diff --git a/cmd/tendermint/commands/gen_validator.go b/cmd/tendermint/commands/gen_validator.go
index 97c583c22..984176d2a 100644
--- a/cmd/tendermint/commands/gen_validator.go
+++ b/cmd/tendermint/commands/gen_validator.go
@@ -9,18 +9,16 @@ import (
 	"github.com/tendermint/tendermint/types"
 )
 
-var genValidatorCmd = &cobra.Command{
+// GenValidatorCmd allows the generation of a keypair for a
+// validator.
+var GenValidatorCmd = &cobra.Command{
 	Use:   "gen_validator",
 	Short: "Generate new validator keypair",
 	Run:   genValidator,
 }
 
-func init() {
-	RootCmd.AddCommand(genValidatorCmd)
-}
-
 func genValidator(cmd *cobra.Command, args []string) {
-	privValidator := types.GenPrivValidator()
+	privValidator := types.GenPrivValidatorFS("")
 	privValidatorJSONBytes, _ := json.MarshalIndent(privValidator, "", "\t")
 	fmt.Printf(`%v
 `, string(privValidatorJSONBytes))
diff --git a/cmd/tendermint/commands/init.go b/cmd/tendermint/commands/init.go
index ce900defa..cbafac3ef 100644
--- a/cmd/tendermint/commands/init.go
+++ b/cmd/tendermint/commands/init.go
@@ -9,21 +9,17 @@ import (
 	cmn "github.com/tendermint/tmlibs/common"
 )
 
-var initFilesCmd = &cobra.Command{
+// InitFilesCmd initialises a fresh Tendermint Core instance.
+var InitFilesCmd = &cobra.Command{
 	Use:   "init",
 	Short: "Initialize Tendermint",
 	Run:   initFiles,
 }
 
-func init() {
-	RootCmd.AddCommand(initFilesCmd)
-}
-
 func initFiles(cmd *cobra.Command, args []string) {
 	privValFile := config.PrivValidatorFile()
 	if _, err := os.Stat(privValFile); os.IsNotExist(err) {
-		privValidator := types.GenPrivValidator()
-		privValidator.SetFile(privValFile)
+		privValidator := types.GenPrivValidatorFS(privValFile)
 		privValidator.Save()
 
 		genFile := config.GenesisFile()
@@ -33,7 +29,7 @@ func initFiles(cmd *cobra.Command, args []string) {
 				ChainID: cmn.Fmt("test-chain-%v", cmn.RandStr(6)),
 			}
 			genDoc.Validators = []types.GenesisValidator{types.GenesisValidator{
-				PubKey: privValidator.PubKey,
+				PubKey: privValidator.GetPubKey(),
 				Power:  10,
 			}}
 
diff --git a/cmd/tendermint/commands/probe_upnp.go b/cmd/tendermint/commands/probe_upnp.go
index e23e48973..643b7713f 100644
--- a/cmd/tendermint/commands/probe_upnp.go
+++ b/cmd/tendermint/commands/probe_upnp.go
@@ -9,16 +9,13 @@ import (
 	"github.com/tendermint/tendermint/p2p/upnp"
 )
 
-var probeUpnpCmd = &cobra.Command{
+// ProbeUpnpCmd adds capabilities to test the UPnP functionality.
+var ProbeUpnpCmd = &cobra.Command{
 	Use:   "probe_upnp",
 	Short: "Test UPnP functionality",
 	RunE:  probeUpnp,
 }
 
-func init() {
-	RootCmd.AddCommand(probeUpnpCmd)
-}
-
 func probeUpnp(cmd *cobra.Command, args []string) error {
 	capabilities, err := upnp.Probe(logger)
 	if err != nil {
diff --git a/cmd/tendermint/commands/replay.go b/cmd/tendermint/commands/replay.go
index 0c88b2443..303ccba6b 100644
--- a/cmd/tendermint/commands/replay.go
+++ b/cmd/tendermint/commands/replay.go
@@ -6,7 +6,8 @@ import (
 	"github.com/tendermint/tendermint/consensus"
 )
 
-var replayCmd = &cobra.Command{
+// ReplayCmd allows replaying of messages from the WAL.
+var ReplayCmd = &cobra.Command{
 	Use:   "replay",
 	Short: "Replay messages from WAL",
 	Run: func(cmd *cobra.Command, args []string) {
@@ -14,15 +15,12 @@ var replayCmd = &cobra.Command{
 	},
 }
 
-var replayConsoleCmd = &cobra.Command{
+// ReplayConsoleCmd allows replaying of messages from the WAL in a
+// console.
+var ReplayConsoleCmd = &cobra.Command{
 	Use:   "replay_console",
 	Short: "Replay messages from WAL in a console",
 	Run: func(cmd *cobra.Command, args []string) {
 		consensus.RunReplayFile(config.BaseConfig, config.Consensus, true)
 	},
 }
-
-func init() {
-	RootCmd.AddCommand(replayCmd)
-	RootCmd.AddCommand(replayConsoleCmd)
-}
diff --git a/cmd/tendermint/commands/reset_priv_validator.go b/cmd/tendermint/commands/reset_priv_validator.go
index fa12be4ea..b9c08715f 100644
--- a/cmd/tendermint/commands/reset_priv_validator.go
+++ b/cmd/tendermint/commands/reset_priv_validator.go
@@ -9,21 +9,27 @@ import (
 	"github.com/tendermint/tmlibs/log"
 )
 
-var resetAllCmd = &cobra.Command{
+// ResetAllCmd removes the database of this Tendermint core
+// instance.
+var ResetAllCmd = &cobra.Command{
 	Use:   "unsafe_reset_all",
 	Short: "(unsafe) Remove all the data and WAL, reset this node's validator",
 	Run:   resetAll,
 }
 
-var resetPrivValidatorCmd = &cobra.Command{
+// ResetPrivValidatorCmd resets the private validator files.
+var ResetPrivValidatorCmd = &cobra.Command{
 	Use:   "unsafe_reset_priv_validator",
 	Short: "(unsafe) Reset this node's validator",
 	Run:   resetPrivValidator,
 }
 
-func init() {
-	RootCmd.AddCommand(resetAllCmd)
-	RootCmd.AddCommand(resetPrivValidatorCmd)
+// ResetAll removes the privValidator files.
+// Exported so other CLI tools can use  it
+func ResetAll(dbDir, privValFile string, logger log.Logger) {
+	resetPrivValidatorFS(privValFile, logger)
+	os.RemoveAll(dbDir)
+	logger.Info("Removed all data", "dir", dbDir)
 }
 
 // XXX: this is totally unsafe.
@@ -35,26 +41,17 @@ func resetAll(cmd *cobra.Command, args []string) {
 // XXX: this is totally unsafe.
 // it's only suitable for testnets.
 func resetPrivValidator(cmd *cobra.Command, args []string) {
-	resetPrivValidatorLocal(config.PrivValidatorFile(), logger)
+	resetPrivValidatorFS(config.PrivValidatorFile(), logger)
 }
 
-// Exported so other CLI tools can use  it
-func ResetAll(dbDir, privValFile string, logger log.Logger) {
-	resetPrivValidatorLocal(privValFile, logger)
-	os.RemoveAll(dbDir)
-	logger.Info("Removed all data", "dir", dbDir)
-}
-
-func resetPrivValidatorLocal(privValFile string, logger log.Logger) {
+func resetPrivValidatorFS(privValFile string, logger log.Logger) {
 	// Get PrivValidator
-	var privValidator *types.PrivValidator
 	if _, err := os.Stat(privValFile); err == nil {
-		privValidator = types.LoadPrivValidator(privValFile)
+		privValidator := types.LoadPrivValidatorFS(privValFile)
 		privValidator.Reset()
 		logger.Info("Reset PrivValidator", "file", privValFile)
 	} else {
-		privValidator = types.GenPrivValidator()
-		privValidator.SetFile(privValFile)
+		privValidator := types.GenPrivValidatorFS(privValFile)
 		privValidator.Save()
 		logger.Info("Generated PrivValidator", "file", privValFile)
 	}
diff --git a/cmd/tendermint/commands/root.go b/cmd/tendermint/commands/root.go
index 6cef5daa9..a54b50069 100644
--- a/cmd/tendermint/commands/root.go
+++ b/cmd/tendermint/commands/root.go
@@ -34,11 +34,12 @@ func ParseConfig() (*cfg.Config, error) {
 	return conf, err
 }
 
+// RootCmd is the root command for Tendermint core.
 var RootCmd = &cobra.Command{
 	Use:   "tendermint",
 	Short: "Tendermint Core (BFT Consensus) in Go",
 	PersistentPreRunE: func(cmd *cobra.Command, args []string) (err error) {
-		if cmd.Name() == versionCmd.Name() {
+		if cmd.Name() == VersionCmd.Name() {
 			return nil
 		}
 		config, err = ParseConfig()
diff --git a/cmd/tendermint/commands/run_node.go b/cmd/tendermint/commands/run_node.go
index 6740df289..f0a1eede2 100644
--- a/cmd/tendermint/commands/run_node.go
+++ b/cmd/tendermint/commands/run_node.go
@@ -5,21 +5,9 @@ import (
 
 	"github.com/spf13/cobra"
 
-	"github.com/tendermint/tendermint/node"
-	"github.com/tendermint/tendermint/types"
+	nm "github.com/tendermint/tendermint/node"
 )
 
-var runNodeCmd = &cobra.Command{
-	Use:   "node",
-	Short: "Run the tendermint node",
-	RunE:  runNode,
-}
-
-func init() {
-	AddNodeFlags(runNodeCmd)
-	RootCmd.AddCommand(runNodeCmd)
-}
-
 // AddNodeFlags exposes some common configuration options on the command-line
 // These are exposed for convenience of commands embedding a tendermint node
 func AddNodeFlags(cmd *cobra.Command) {
@@ -48,31 +36,32 @@ func AddNodeFlags(cmd *cobra.Command) {
 	cmd.Flags().Bool("consensus.create_empty_blocks", config.Consensus.CreateEmptyBlocks, "Set this to false to only produce blocks when there are txs or when the AppHash changes")
 }
 
-// Users wishing to:
-//	* Use an external signer for their validators
-//	* Supply an in-proc abci app
-// should import github.com/tendermint/tendermint/node and implement
-// their own run_node to call node.NewNode (instead of node.NewNodeDefault)
-// with their custom priv validator and/or custom proxy.ClientCreator
-func runNode(cmd *cobra.Command, args []string) error {
+// NewRunNodeCmd returns the command that allows the CLI to start a
+// node. It can be used with a custom PrivValidator and in-process ABCI application.
+func NewRunNodeCmd(nodeProvider nm.NodeProvider) *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "node",
+		Short: "Run the tendermint node",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			// Create & start node
+			n, err := nodeProvider(config, logger)
+			if err != nil {
+				return fmt.Errorf("Failed to create node: %v", err)
+			}
 
-	genDocFile := config.GenesisFile()
-	genDoc, err := types.GenesisDocFromFile(genDocFile)
-	if err != nil {
-		return err
-	}
-	config.ChainID = genDoc.ChainID
+			if _, err := n.Start(); err != nil {
+				return fmt.Errorf("Failed to start node: %v", err)
+			} else {
+				logger.Info("Started node", "nodeInfo", n.Switch().NodeInfo())
+			}
 
-	// Create & start node
-	n := node.NewNodeDefault(config, logger.With("module", "node"))
-	if _, err := n.Start(); err != nil {
-		return fmt.Errorf("Failed to start node: %v", err)
-	} else {
-		logger.Info("Started node", "nodeInfo", n.Switch().NodeInfo())
+			// Trap signal, run forever.
+			n.RunForever()
+
+			return nil
+		},
 	}
 
-	// Trap signal, run forever.
-	n.RunForever()
-
-	return nil
+	AddNodeFlags(cmd)
+	return cmd
 }
diff --git a/cmd/tendermint/commands/show_validator.go b/cmd/tendermint/commands/show_validator.go
index 53a687c6d..458f11c2d 100644
--- a/cmd/tendermint/commands/show_validator.go
+++ b/cmd/tendermint/commands/show_validator.go
@@ -9,18 +9,15 @@ import (
 	"github.com/tendermint/tendermint/types"
 )
 
-var showValidatorCmd = &cobra.Command{
+// ShowValidatorCmd adds capabilities for showing the validator info.
+var ShowValidatorCmd = &cobra.Command{
 	Use:   "show_validator",
 	Short: "Show this node's validator info",
 	Run:   showValidator,
 }
 
-func init() {
-	RootCmd.AddCommand(showValidatorCmd)
-}
-
 func showValidator(cmd *cobra.Command, args []string) {
-	privValidator := types.LoadOrGenPrivValidator(config.PrivValidatorFile(), logger)
+	privValidator := types.LoadOrGenPrivValidatorFS(config.PrivValidatorFile())
 	pubKeyJSONBytes, _ := data.ToJSON(privValidator.PubKey)
 	fmt.Println(string(pubKeyJSONBytes))
 }
diff --git a/cmd/tendermint/commands/testnet.go b/cmd/tendermint/commands/testnet.go
index 315f3b498..ac6f337a9 100644
--- a/cmd/tendermint/commands/testnet.go
+++ b/cmd/tendermint/commands/testnet.go
@@ -11,12 +11,6 @@ import (
 	cmn "github.com/tendermint/tmlibs/common"
 )
 
-var testnetFilesCmd = &cobra.Command{
-	Use:   "testnet",
-	Short: "Initialize files for a Tendermint testnet",
-	Run:   testnetFiles,
-}
-
 //flags
 var (
 	nValidators int
@@ -24,12 +18,18 @@ var (
 )
 
 func init() {
-	testnetFilesCmd.Flags().IntVar(&nValidators, "n", 4,
+	TestnetFilesCmd.Flags().IntVar(&nValidators, "n", 4,
 		"Number of validators to initialize the testnet with")
-	testnetFilesCmd.Flags().StringVar(&dataDir, "dir", "mytestnet",
+	TestnetFilesCmd.Flags().StringVar(&dataDir, "dir", "mytestnet",
 		"Directory to store initialization data for the testnet")
+}
 
-	RootCmd.AddCommand(testnetFilesCmd)
+// TestnetFilesCmd allows initialisation of files for a
+// Tendermint testnet.
+var TestnetFilesCmd = &cobra.Command{
+	Use:   "testnet",
+	Short: "Initialize files for a Tendermint testnet",
+	Run:   testnetFiles,
 }
 
 func testnetFiles(cmd *cobra.Command, args []string) {
@@ -45,9 +45,9 @@ func testnetFiles(cmd *cobra.Command, args []string) {
 		}
 		// Read priv_validator.json to populate vals
 		privValFile := path.Join(dataDir, mach, "priv_validator.json")
-		privVal := types.LoadPrivValidator(privValFile)
+		privVal := types.LoadPrivValidatorFS(privValFile)
 		genVals[i] = types.GenesisValidator{
-			PubKey: privVal.PubKey,
+			PubKey: privVal.GetPubKey(),
 			Power:  1,
 			Name:   mach,
 		}
@@ -87,7 +87,6 @@ func ensurePrivValidator(file string) {
 	if cmn.FileExists(file) {
 		return
 	}
-	privValidator := types.GenPrivValidator()
-	privValidator.SetFile(file)
+	privValidator := types.GenPrivValidatorFS(file)
 	privValidator.Save()
 }
diff --git a/cmd/tendermint/commands/version.go b/cmd/tendermint/commands/version.go
index 5c92160ea..f9f545e59 100644
--- a/cmd/tendermint/commands/version.go
+++ b/cmd/tendermint/commands/version.go
@@ -8,14 +8,11 @@ import (
 	"github.com/tendermint/tendermint/version"
 )
 
-var versionCmd = &cobra.Command{
+// VersionCmd ...
+var VersionCmd = &cobra.Command{
 	Use:   "version",
 	Short: "Show version info",
 	Run: func(cmd *cobra.Command, args []string) {
 		fmt.Println(version.Version)
 	},
 }
-
-func init() {
-	RootCmd.AddCommand(versionCmd)
-}
diff --git a/cmd/tendermint/main.go b/cmd/tendermint/main.go
index 5493e4f2f..86ca1531d 100644
--- a/cmd/tendermint/main.go
+++ b/cmd/tendermint/main.go
@@ -3,11 +3,39 @@ package main
 import (
 	"os"
 
-	"github.com/tendermint/tendermint/cmd/tendermint/commands"
 	"github.com/tendermint/tmlibs/cli"
+
+	cmd "github.com/tendermint/tendermint/cmd/tendermint/commands"
+	nm "github.com/tendermint/tendermint/node"
 )
 
 func main() {
-	cmd := cli.PrepareBaseCmd(commands.RootCmd, "TM", os.ExpandEnv("$HOME/.tendermint"))
+	rootCmd := cmd.RootCmd
+	rootCmd.AddCommand(
+		cmd.GenValidatorCmd,
+		cmd.InitFilesCmd,
+		cmd.ProbeUpnpCmd,
+		cmd.ReplayCmd,
+		cmd.ReplayConsoleCmd,
+		cmd.ResetAllCmd,
+		cmd.ResetPrivValidatorCmd,
+		cmd.ShowValidatorCmd,
+		cmd.TestnetFilesCmd,
+		cmd.VersionCmd)
+
+	// NOTE:
+	// Users wishing to:
+	//	* Use an external signer for their validators
+	//	* Supply an in-proc abci app
+	//	* Supply a genesis doc file from another source
+	//	* Provide their own DB implementation
+	// can copy this file and use something other than the
+	// DefaultNewNode function
+	nodeFunc := nm.DefaultNewNode
+
+	// Create & start node
+	rootCmd.AddCommand(cmd.NewRunNodeCmd(nodeFunc))
+
+	cmd := cli.PrepareBaseCmd(rootCmd, "TM", os.ExpandEnv("$HOME/.tendermint"))
 	cmd.Execute()
 }
diff --git a/consensus/byzantine_test.go b/consensus/byzantine_test.go
index 81a4ab42c..0f2d7b040 100644
--- a/consensus/byzantine_test.go
+++ b/consensus/byzantine_test.go
@@ -5,6 +5,8 @@ import (
 	"testing"
 	"time"
 
+	crypto "github.com/tendermint/go-crypto"
+	data "github.com/tendermint/go-wire/data"
 	"github.com/tendermint/tendermint/p2p"
 	"github.com/tendermint/tendermint/types"
 	. "github.com/tendermint/tmlibs/common"
@@ -53,7 +55,7 @@ func TestByzantine(t *testing.T) {
 	eventLogger := logger.With("module", "events")
 	for i := 0; i < N; i++ {
 		if i == 0 {
-			css[i].privValidator = NewByzantinePrivValidator(css[i].privValidator.(*types.PrivValidator))
+			css[i].privValidator = NewByzantinePrivValidator(css[i].privValidator)
 			// make byzantine
 			css[i].decideProposal = func(j int) func(int, int) {
 				return func(height, round int) {
@@ -257,51 +259,42 @@ func (br *ByzantineReactor) Receive(chID byte, peer p2p.Peer, msgBytes []byte) {
 // byzantine privValidator
 
 type ByzantinePrivValidator struct {
-	Address      []byte `json:"address"`
-	types.Signer `json:"-"`
+	types.Signer
 
-	mtx sync.Mutex
+	pv types.PrivValidator
 }
 
 // Return a priv validator that will sign anything
-func NewByzantinePrivValidator(pv *types.PrivValidator) *ByzantinePrivValidator {
+func NewByzantinePrivValidator(pv types.PrivValidator) *ByzantinePrivValidator {
 	return &ByzantinePrivValidator{
-		Address: pv.Address,
-		Signer:  pv.Signer,
+		Signer: pv.(*types.PrivValidatorFS).Signer,
+		pv:     pv,
 	}
 }
 
-func (privVal *ByzantinePrivValidator) GetAddress() []byte {
-	return privVal.Address
+func (privVal *ByzantinePrivValidator) GetAddress() data.Bytes {
+	return privVal.pv.GetAddress()
+}
+
+func (privVal *ByzantinePrivValidator) GetPubKey() crypto.PubKey {
+	return privVal.pv.GetPubKey()
 }
 
 func (privVal *ByzantinePrivValidator) SignVote(chainID string, vote *types.Vote) (err error) {
-	privVal.mtx.Lock()
-	defer privVal.mtx.Unlock()
-
-	// Sign
 	vote.Signature, err = privVal.Sign(types.SignBytes(chainID, vote))
 	return err
 }
 
 func (privVal *ByzantinePrivValidator) SignProposal(chainID string, proposal *types.Proposal) (err error) {
-	privVal.mtx.Lock()
-	defer privVal.mtx.Unlock()
-
-	// Sign
 	proposal.Signature, err = privVal.Sign(types.SignBytes(chainID, proposal))
 	return nil
 }
 
 func (privVal *ByzantinePrivValidator) SignHeartbeat(chainID string, heartbeat *types.Heartbeat) (err error) {
-	privVal.mtx.Lock()
-	defer privVal.mtx.Unlock()
-
-	// Sign
 	heartbeat.Signature, err = privVal.Sign(types.SignBytes(chainID, heartbeat))
 	return nil
 }
 
 func (privVal *ByzantinePrivValidator) String() string {
-	return Fmt("PrivValidator{%X}", privVal.Address)
+	return Fmt("PrivValidator{%X}", privVal.GetAddress())
 }
diff --git a/consensus/common_test.go b/consensus/common_test.go
index 6a05b74e3..b16afc3d0 100644
--- a/consensus/common_test.go
+++ b/consensus/common_test.go
@@ -50,12 +50,12 @@ type validatorStub struct {
 	Index  int // Validator index. NOTE: we don't assume validator set changes.
 	Height int
 	Round  int
-	*types.PrivValidator
+	types.PrivValidator
 }
 
 var testMinPower = 10
 
-func NewValidatorStub(privValidator *types.PrivValidator, valIndex int) *validatorStub {
+func NewValidatorStub(privValidator types.PrivValidator, valIndex int) *validatorStub {
 	return &validatorStub{
 		Index:         valIndex,
 		PrivValidator: privValidator,
@@ -65,7 +65,7 @@ func NewValidatorStub(privValidator *types.PrivValidator, valIndex int) *validat
 func (vs *validatorStub) signVote(voteType byte, hash []byte, header types.PartSetHeader) (*types.Vote, error) {
 	vote := &types.Vote{
 		ValidatorIndex:   vs.Index,
-		ValidatorAddress: vs.PrivValidator.Address,
+		ValidatorAddress: vs.PrivValidator.GetAddress(),
 		Height:           vs.Height,
 		Round:            vs.Round,
 		Type:             voteType,
@@ -142,7 +142,7 @@ func signAddVotes(to *ConsensusState, voteType byte, hash []byte, header types.P
 func validatePrevote(t *testing.T, cs *ConsensusState, round int, privVal *validatorStub, blockHash []byte) {
 	prevotes := cs.Votes.Prevotes(round)
 	var vote *types.Vote
-	if vote = prevotes.GetByAddress(privVal.Address); vote == nil {
+	if vote = prevotes.GetByAddress(privVal.GetAddress()); vote == nil {
 		panic("Failed to find prevote from validator")
 	}
 	if blockHash == nil {
@@ -159,7 +159,7 @@ func validatePrevote(t *testing.T, cs *ConsensusState, round int, privVal *valid
 func validateLastPrecommit(t *testing.T, cs *ConsensusState, privVal *validatorStub, blockHash []byte) {
 	votes := cs.LastCommit
 	var vote *types.Vote
-	if vote = votes.GetByAddress(privVal.Address); vote == nil {
+	if vote = votes.GetByAddress(privVal.GetAddress()); vote == nil {
 		panic("Failed to find precommit from validator")
 	}
 	if !bytes.Equal(vote.BlockID.Hash, blockHash) {
@@ -170,7 +170,7 @@ func validateLastPrecommit(t *testing.T, cs *ConsensusState, privVal *validatorS
 func validatePrecommit(t *testing.T, cs *ConsensusState, thisRound, lockRound int, privVal *validatorStub, votedBlockHash, lockedBlockHash []byte) {
 	precommits := cs.Votes.Precommits(thisRound)
 	var vote *types.Vote
-	if vote = precommits.GetByAddress(privVal.Address); vote == nil {
+	if vote = precommits.GetByAddress(privVal.GetAddress()); vote == nil {
 		panic("Failed to find precommit from validator")
 	}
 
@@ -225,11 +225,11 @@ func subscribeToVoter(cs *ConsensusState, addr []byte) chan interface{} {
 //-------------------------------------------------------------------------------
 // consensus states
 
-func newConsensusState(state *sm.State, pv *types.PrivValidator, app abci.Application) *ConsensusState {
+func newConsensusState(state *sm.State, pv types.PrivValidator, app abci.Application) *ConsensusState {
 	return newConsensusStateWithConfig(config, state, pv, app)
 }
 
-func newConsensusStateWithConfig(thisConfig *cfg.Config, state *sm.State, pv *types.PrivValidator, app abci.Application) *ConsensusState {
+func newConsensusStateWithConfig(thisConfig *cfg.Config, state *sm.State, pv types.PrivValidator, app abci.Application) *ConsensusState {
 	// Get BlockStore
 	blockDB := dbm.NewMemDB()
 	blockStore := bc.NewBlockStore(blockDB)
@@ -258,17 +258,17 @@ func newConsensusStateWithConfig(thisConfig *cfg.Config, state *sm.State, pv *ty
 	return cs
 }
 
-func loadPrivValidator(config *cfg.Config) *types.PrivValidator {
+func loadPrivValidator(config *cfg.Config) *types.PrivValidatorFS {
 	privValidatorFile := config.PrivValidatorFile()
 	ensureDir(path.Dir(privValidatorFile), 0700)
-	privValidator := types.LoadOrGenPrivValidator(privValidatorFile, log.TestingLogger())
+	privValidator := types.LoadOrGenPrivValidatorFS(privValidatorFile)
 	privValidator.Reset()
 	return privValidator
 }
 
 func fixedConsensusStateDummy() *ConsensusState {
 	stateDB := dbm.NewMemDB()
-	state := sm.MakeGenesisStateFromFile(stateDB, config.GenesisFile())
+	state, _ := sm.MakeGenesisStateFromFile(stateDB, config.GenesisFile())
 	state.SetLogger(log.TestingLogger().With("module", "state"))
 	privValidator := loadPrivValidator(config)
 	cs := newConsensusState(state, privValidator, dummy.NewDummyApplication())
@@ -338,7 +338,7 @@ func randConsensusNet(nValidators int, testName string, tickerFunc func() Timeou
 	logger := consensusLogger()
 	for i := 0; i < nValidators; i++ {
 		db := dbm.NewMemDB() // each state needs its own db
-		state := sm.MakeGenesisState(db, genDoc)
+		state, _ := sm.MakeGenesisState(db, genDoc)
 		state.SetLogger(logger.With("module", "state", "validator", i))
 		state.Save()
 		thisConfig := ResetConfig(Fmt("%s_%d", testName, i))
@@ -359,18 +359,17 @@ func randConsensusNetWithPeers(nValidators, nPeers int, testName string, tickerF
 	css := make([]*ConsensusState, nPeers)
 	for i := 0; i < nPeers; i++ {
 		db := dbm.NewMemDB() // each state needs its own db
-		state := sm.MakeGenesisState(db, genDoc)
+		state, _ := sm.MakeGenesisState(db, genDoc)
 		state.SetLogger(log.TestingLogger().With("module", "state"))
 		state.Save()
 		thisConfig := ResetConfig(Fmt("%s_%d", testName, i))
 		ensureDir(path.Dir(thisConfig.Consensus.WalFile()), 0700) // dir for wal
-		var privVal *types.PrivValidator
+		var privVal types.PrivValidator
 		if i < nValidators {
 			privVal = privVals[i]
 		} else {
-			privVal = types.GenPrivValidator()
 			_, tempFilePath := Tempfile("priv_validator_")
-			privVal.SetFile(tempFilePath)
+			privVal = types.GenPrivValidatorFS(tempFilePath)
 		}
 
 		css[i] = newConsensusStateWithConfig(thisConfig, state, privVal, appFunc())
@@ -393,9 +392,9 @@ func getSwitchIndex(switches []*p2p.Switch, peer p2p.Peer) int {
 //-------------------------------------------------------------------------------
 // genesis
 
-func randGenesisDoc(numValidators int, randPower bool, minPower int64) (*types.GenesisDoc, []*types.PrivValidator) {
+func randGenesisDoc(numValidators int, randPower bool, minPower int64) (*types.GenesisDoc, []*types.PrivValidatorFS) {
 	validators := make([]types.GenesisValidator, numValidators)
-	privValidators := make([]*types.PrivValidator, numValidators)
+	privValidators := make([]*types.PrivValidatorFS, numValidators)
 	for i := 0; i < numValidators; i++ {
 		val, privVal := types.RandValidator(randPower, minPower)
 		validators[i] = types.GenesisValidator{
@@ -412,10 +411,10 @@ func randGenesisDoc(numValidators int, randPower bool, minPower int64) (*types.G
 	}, privValidators
 }
 
-func randGenesisState(numValidators int, randPower bool, minPower int64) (*sm.State, []*types.PrivValidator) {
+func randGenesisState(numValidators int, randPower bool, minPower int64) (*sm.State, []*types.PrivValidatorFS) {
 	genDoc, privValidators := randGenesisDoc(numValidators, randPower, minPower)
 	db := dbm.NewMemDB()
-	s0 := sm.MakeGenesisState(db, genDoc)
+	s0, _ := sm.MakeGenesisState(db, genDoc)
 	s0.SetLogger(log.TestingLogger().With("module", "state"))
 	s0.Save()
 	return s0, privValidators
diff --git a/consensus/height_vote_set_test.go b/consensus/height_vote_set_test.go
index 29751b40a..7e03e40f5 100644
--- a/consensus/height_vote_set_test.go
+++ b/consensus/height_vote_set_test.go
@@ -44,10 +44,10 @@ func TestPeerCatchupRounds(t *testing.T) {
 
 }
 
-func makeVoteHR(t *testing.T, height, round int, privVals []*types.PrivValidator, valIndex int) *types.Vote {
+func makeVoteHR(t *testing.T, height, round int, privVals []*types.PrivValidatorFS, valIndex int) *types.Vote {
 	privVal := privVals[valIndex]
 	vote := &types.Vote{
-		ValidatorAddress: privVal.Address,
+		ValidatorAddress: privVal.GetAddress(),
 		ValidatorIndex:   valIndex,
 		Height:           height,
 		Round:            round,
diff --git a/consensus/reactor_test.go b/consensus/reactor_test.go
index b1f9a0a5b..623a65413 100644
--- a/consensus/reactor_test.go
+++ b/consensus/reactor_test.go
@@ -132,7 +132,7 @@ func TestVotingPowerChange(t *testing.T) {
 	//---------------------------------------------------------------------------
 	t.Log("---------------------------- Testing changing the voting power of one validator a few times")
 
-	val1PubKey := css[0].privValidator.(*types.PrivValidator).PubKey
+	val1PubKey := css[0].privValidator.GetPubKey()
 	updateValidatorTx := dummy.MakeValSetChangeTx(val1PubKey.Bytes(), 25)
 	previousTotalVotingPower := css[0].GetRoundState().LastValidators.TotalVotingPower()
 
@@ -193,7 +193,7 @@ func TestValidatorSetChanges(t *testing.T) {
 	//---------------------------------------------------------------------------
 	t.Log("---------------------------- Testing adding one validator")
 
-	newValidatorPubKey1 := css[nVals].privValidator.(*types.PrivValidator).PubKey
+	newValidatorPubKey1 := css[nVals].privValidator.GetPubKey()
 	newValidatorTx1 := dummy.MakeValSetChangeTx(newValidatorPubKey1.Bytes(), uint64(testMinPower))
 
 	// wait till everyone makes block 2
@@ -219,7 +219,7 @@ func TestValidatorSetChanges(t *testing.T) {
 	//---------------------------------------------------------------------------
 	t.Log("---------------------------- Testing changing the voting power of one validator")
 
-	updateValidatorPubKey1 := css[nVals].privValidator.(*types.PrivValidator).PubKey
+	updateValidatorPubKey1 := css[nVals].privValidator.GetPubKey()
 	updateValidatorTx1 := dummy.MakeValSetChangeTx(updateValidatorPubKey1.Bytes(), 25)
 	previousTotalVotingPower := css[nVals].GetRoundState().LastValidators.TotalVotingPower()
 
@@ -235,10 +235,10 @@ func TestValidatorSetChanges(t *testing.T) {
 	//---------------------------------------------------------------------------
 	t.Log("---------------------------- Testing adding two validators at once")
 
-	newValidatorPubKey2 := css[nVals+1].privValidator.(*types.PrivValidator).PubKey
+	newValidatorPubKey2 := css[nVals+1].privValidator.GetPubKey()
 	newValidatorTx2 := dummy.MakeValSetChangeTx(newValidatorPubKey2.Bytes(), uint64(testMinPower))
 
-	newValidatorPubKey3 := css[nVals+2].privValidator.(*types.PrivValidator).PubKey
+	newValidatorPubKey3 := css[nVals+2].privValidator.GetPubKey()
 	newValidatorTx3 := dummy.MakeValSetChangeTx(newValidatorPubKey3.Bytes(), uint64(testMinPower))
 
 	waitForAndValidateBlock(t, nPeers, activeVals, eventChans, css, newValidatorTx2, newValidatorTx3)
diff --git a/consensus/replay_file.go b/consensus/replay_file.go
index 39ce47c5e..1182aaf04 100644
--- a/consensus/replay_file.go
+++ b/consensus/replay_file.go
@@ -241,12 +241,15 @@ func newConsensusStateForReplay(config cfg.BaseConfig, csConfig *cfg.ConsensusCo
 
 	// Get State
 	stateDB := dbm.NewDB("state", config.DBBackend, config.DBDir())
-	state := sm.MakeGenesisStateFromFile(stateDB, config.GenesisFile())
+	state, err := sm.MakeGenesisStateFromFile(stateDB, config.GenesisFile())
+	if err != nil {
+		cmn.Exit(err.Error())
+	}
 
 	// Create proxyAppConn connection (consensus, mempool, query)
 	clientCreator := proxy.DefaultClientCreator(config.ProxyApp, config.ABCI, config.DBDir())
 	proxyApp := proxy.NewAppConns(clientCreator, NewHandshaker(state, blockStore))
-	_, err := proxyApp.Start()
+	_, err = proxyApp.Start()
 	if err != nil {
 		cmn.Exit(cmn.Fmt("Error starting proxy app conns: %v", err))
 	}
diff --git a/consensus/replay_test.go b/consensus/replay_test.go
index 03ca6c8d7..765434677 100644
--- a/consensus/replay_test.go
+++ b/consensus/replay_test.go
@@ -162,8 +162,8 @@ LOOP:
 	cs.Wait()
 }
 
-func toPV(pv PrivValidator) *types.PrivValidator {
-	return pv.(*types.PrivValidator)
+func toPV(pv types.PrivValidator) *types.PrivValidatorFS {
+	return pv.(*types.PrivValidatorFS)
 }
 
 func setupReplayTest(t *testing.T, thisCase *testCase, nLines int, crashAfter bool) (*ConsensusState, chan interface{}, string, string) {
@@ -317,7 +317,7 @@ func testHandshakeReplay(t *testing.T, nBlocks int, mode uint) {
 	walFile := writeWAL(string(walBody))
 	config.Consensus.SetWalFile(walFile)
 
-	privVal := types.LoadPrivValidator(config.PrivValidatorFile())
+	privVal := types.LoadPrivValidatorFS(config.PrivValidatorFile())
 
 	wal, err := NewWAL(walFile, false)
 	if err != nil {
@@ -332,7 +332,7 @@ func testHandshakeReplay(t *testing.T, nBlocks int, mode uint) {
 		t.Fatalf(err.Error())
 	}
 
-	state, store := stateAndStore(config, privVal.PubKey)
+	state, store := stateAndStore(config, privVal.GetPubKey())
 	store.chain = chain
 	store.commits = commits
 
@@ -346,7 +346,7 @@ func testHandshakeReplay(t *testing.T, nBlocks int, mode uint) {
 		// run nBlocks against a new client to build up the app state.
 		// use a throwaway tendermint state
 		proxyApp := proxy.NewAppConns(clientCreator2, nil)
-		state, _ := stateAndStore(config, privVal.PubKey)
+		state, _ := stateAndStore(config, privVal.GetPubKey())
 		buildAppStateFromChain(proxyApp, state, chain, nBlocks, mode)
 	}
 
@@ -558,7 +558,7 @@ func readPieceFromWAL(msgBytes []byte) (interface{}, error) {
 // fresh state and mock store
 func stateAndStore(config *cfg.Config, pubKey crypto.PubKey) (*sm.State, *mockBlockStore) {
 	stateDB := dbm.NewMemDB()
-	state := sm.MakeGenesisStateFromFile(stateDB, config.GenesisFile())
+	state, _ := sm.MakeGenesisStateFromFile(stateDB, config.GenesisFile())
 	state.SetLogger(log.TestingLogger().With("module", "state"))
 
 	store := NewMockBlockStore(config, state.Params())
diff --git a/consensus/state.go b/consensus/state.go
index ac1656209..648fc0559 100644
--- a/consensus/state.go
+++ b/consensus/state.go
@@ -180,14 +180,6 @@ func (ti *timeoutInfo) String() string {
 	return fmt.Sprintf("%v ; %d/%d %v", ti.Duration, ti.Height, ti.Round, ti.Step)
 }
 
-// PrivValidator is a validator that can sign votes and proposals.
-type PrivValidator interface {
-	GetAddress() []byte
-	SignVote(chainID string, vote *types.Vote) error
-	SignProposal(chainID string, proposal *types.Proposal) error
-	SignHeartbeat(chainID string, heartbeat *types.Heartbeat) error
-}
-
 // ConsensusState handles execution of the consensus algorithm.
 // It processes votes and proposals, and upon reaching agreement,
 // commits blocks to the chain and executes them against the application.
@@ -197,7 +189,7 @@ type ConsensusState struct {
 
 	// config details
 	config        *cfg.ConsensusConfig
-	privValidator PrivValidator // for signing votes
+	privValidator types.PrivValidator // for signing votes
 
 	// services for creating and executing blocks
 	proxyAppConn proxy.AppConnConsensus
@@ -308,7 +300,7 @@ func (cs *ConsensusState) GetValidators() (int, []*types.Validator) {
 }
 
 // SetPrivValidator sets the private validator account for signing votes.
-func (cs *ConsensusState) SetPrivValidator(priv PrivValidator) {
+func (cs *ConsensusState) SetPrivValidator(priv types.PrivValidator) {
 	cs.mtx.Lock()
 	defer cs.mtx.Unlock()
 	cs.privValidator = priv
diff --git a/consensus/state_test.go b/consensus/state_test.go
index 9ae052033..c4a6769e9 100644
--- a/consensus/state_test.go
+++ b/consensus/state_test.go
@@ -79,7 +79,7 @@ func TestProposerSelection0(t *testing.T) {
 	<-newRoundCh
 
 	prop = cs1.GetRoundState().Validators.GetProposer()
-	if !bytes.Equal(prop.Address, vss[1].Address) {
+	if !bytes.Equal(prop.Address, vss[1].GetAddress()) {
 		panic(Fmt("expected proposer to be validator %d. Got %X", 1, prop.Address))
 	}
 }
@@ -100,7 +100,7 @@ func TestProposerSelection2(t *testing.T) {
 	// everyone just votes nil. we get a new proposer each round
 	for i := 0; i < len(vss); i++ {
 		prop := cs1.GetRoundState().Validators.GetProposer()
-		if !bytes.Equal(prop.Address, vss[(i+2)%len(vss)].Address) {
+		if !bytes.Equal(prop.Address, vss[(i+2)%len(vss)].GetAddress()) {
 			panic(Fmt("expected proposer to be validator %d. Got %X", (i+2)%len(vss), prop.Address))
 		}
 
@@ -502,8 +502,6 @@ func TestLockPOLRelock(t *testing.T) {
 	newRoundCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringNewRound(), 1)
 	newBlockCh := subscribeToEvent(cs1.evsw, "tester", types.EventStringNewBlockHeader(), 1)
 
-	t.Logf("vs2 last round %v", vs2.PrivValidator.LastRound)
-
 	// everything done from perspective of cs1
 
 	/*
diff --git a/node/node.go b/node/node.go
index e0ddeb5d4..4286fece2 100644
--- a/node/node.go
+++ b/node/node.go
@@ -3,6 +3,7 @@ package node
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"net"
 	"net/http"
 	"strings"
@@ -10,11 +11,15 @@ import (
 	abci "github.com/tendermint/abci/types"
 	crypto "github.com/tendermint/go-crypto"
 	wire "github.com/tendermint/go-wire"
+	cmn "github.com/tendermint/tmlibs/common"
+	dbm "github.com/tendermint/tmlibs/db"
+	"github.com/tendermint/tmlibs/log"
+
 	bc "github.com/tendermint/tendermint/blockchain"
 	cfg "github.com/tendermint/tendermint/config"
 	"github.com/tendermint/tendermint/consensus"
 	mempl "github.com/tendermint/tendermint/mempool"
-	p2p "github.com/tendermint/tendermint/p2p"
+	"github.com/tendermint/tendermint/p2p"
 	"github.com/tendermint/tendermint/proxy"
 	rpccore "github.com/tendermint/tendermint/rpc/core"
 	grpccore "github.com/tendermint/tendermint/rpc/grpc"
@@ -26,20 +31,66 @@ import (
 	"github.com/tendermint/tendermint/state/txindex/null"
 	"github.com/tendermint/tendermint/types"
 	"github.com/tendermint/tendermint/version"
-	cmn "github.com/tendermint/tmlibs/common"
-	dbm "github.com/tendermint/tmlibs/db"
-	"github.com/tendermint/tmlibs/log"
 
 	_ "net/http/pprof"
 )
 
+//------------------------------------------------------------------------------
+
+// DBContext specifies config information for loading a new DB.
+type DBContext struct {
+	ID     string
+	Config *cfg.Config
+}
+
+// DBProvider takes a DBContext and returns an instantiated DB.
+type DBProvider func(*DBContext) (dbm.DB, error)
+
+// DefaultDBProvider returns a database using the DBBackend and DBDir
+// specified in the ctx.Config.
+func DefaultDBProvider(ctx *DBContext) (dbm.DB, error) {
+	return dbm.NewDB(ctx.ID, ctx.Config.DBBackend, ctx.Config.DBDir()), nil
+}
+
+// GenesisDocProvider returns a GenesisDoc.
+// It allows the GenesisDoc to be pulled from sources other than the
+// filesystem, for instance from a distributed key-value store cluster.
+type GenesisDocProvider func() (*types.GenesisDoc, error)
+
+// DefaultGenesisDocProviderFunc returns a GenesisDocProvider that loads
+// the GenesisDoc from the config.GenesisFile() on the filesystem.
+func DefaultGenesisDocProviderFunc(config *cfg.Config) GenesisDocProvider {
+	return func() (*types.GenesisDoc, error) {
+		return types.GenesisDocFromFile(config.GenesisFile())
+	}
+}
+
+// NodeProvider takes a config and a logger and returns a ready to go Node.
+type NodeProvider func(*cfg.Config, log.Logger) (*Node, error)
+
+// DefaultNewNode returns a Tendermint node with default settings for the
+// PrivValidator, ClientCreator, GenesisDoc, and DBProvider.
+// It implements NodeProvider.
+func DefaultNewNode(config *cfg.Config, logger log.Logger) (*Node, error) {
+	return NewNode(config,
+		types.LoadOrGenPrivValidatorFS(config.PrivValidatorFile()),
+		proxy.DefaultClientCreator(config.ProxyApp, config.ABCI, config.DBDir()),
+		DefaultGenesisDocProviderFunc(config),
+		DefaultDBProvider,
+		logger)
+}
+
+//------------------------------------------------------------------------------
+
+// Node is the highest level interface to a full Tendermint node.
+// It includes all configuration information and running services.
 type Node struct {
 	cmn.BaseService
 
 	// config
 	config        *cfg.Config
-	genesisDoc    *types.GenesisDoc    // initial validator set
-	privValidator *types.PrivValidator // local node's validator key
+	genesisDoc    *types.GenesisDoc   // initial validator set
+	privValidator types.PrivValidator // local node's validator key
 
 	// network
 	privKey  crypto.PrivKeyEd25519 // local node's p2p key
@@ -58,24 +109,42 @@ type Node struct {
 	txIndexer        txindex.TxIndexer
 }
 
-func NewNodeDefault(config *cfg.Config, logger log.Logger) *Node {
-	// Get PrivValidator
-	privValidator := types.LoadOrGenPrivValidator(config.PrivValidatorFile(), logger)
-	return NewNode(config, privValidator,
-		proxy.DefaultClientCreator(config.ProxyApp, config.ABCI, config.DBDir()), logger)
-}
+// NewNode returns a new, ready to go, Tendermint Node.
+func NewNode(config *cfg.Config,
+	privValidator types.PrivValidator,
+	clientCreator proxy.ClientCreator,
+	genesisDocProvider GenesisDocProvider,
+	dbProvider DBProvider,
+	logger log.Logger) (*Node, error) {
 
-func NewNode(config *cfg.Config, privValidator *types.PrivValidator, clientCreator proxy.ClientCreator, logger log.Logger) *Node {
 	// Get BlockStore
-	blockStoreDB := dbm.NewDB("blockstore", config.DBBackend, config.DBDir())
+	blockStoreDB, err := dbProvider(&DBContext{"blockstore", config})
+	if err != nil {
+		return nil, err
+	}
 	blockStore := bc.NewBlockStore(blockStoreDB)
 
 	consensusLogger := logger.With("module", "consensus")
 	stateLogger := logger.With("module", "state")
 
 	// Get State
-	stateDB := dbm.NewDB("state", config.DBBackend, config.DBDir())
-	state := sm.GetState(stateDB, config.GenesisFile())
+	stateDB, err := dbProvider(&DBContext{"state", config})
+	if err != nil {
+		return nil, err
+	}
+	state := sm.LoadState(stateDB)
+	if state == nil {
+		genDoc, err := genesisDocProvider()
+		if err != nil {
+			return nil, err
+		}
+		state, err = sm.MakeGenesisState(stateDB, genDoc)
+		if err != nil {
+			return nil, err
+		}
+		state.Save()
+	}
+
 	state.SetLogger(stateLogger)
 
 	// Create the proxyApp, which manages connections (consensus, mempool, query)
@@ -85,7 +154,7 @@ func NewNode(config *cfg.Config, privValidator *types.PrivValidator, clientCreat
 	proxyApp := proxy.NewAppConns(clientCreator, handshaker)
 	proxyApp.SetLogger(logger.With("module", "proxy"))
 	if _, err := proxyApp.Start(); err != nil {
-		cmn.Exit(cmn.Fmt("Error starting proxy app connections: %v", err))
+		return nil, fmt.Errorf("Error starting proxy app connections: %v", err)
 	}
 
 	// reload the state (it may have been updated by the handshake)
@@ -96,7 +165,10 @@ func NewNode(config *cfg.Config, privValidator *types.PrivValidator, clientCreat
 	var txIndexer txindex.TxIndexer
 	switch config.TxIndex {
 	case "kv":
-		store := dbm.NewDB("tx_index", config.DBBackend, config.DBDir())
+		store, err := dbProvider(&DBContext{"tx_index", config})
+		if err != nil {
+			return nil, err
+		}
 		txIndexer = kv.NewTxIndex(store)
 	default:
 		txIndexer = &null.TxIndex{}
@@ -109,9 +181,8 @@ func NewNode(config *cfg.Config, privValidator *types.PrivValidator, clientCreat
 	// Make event switch
 	eventSwitch := types.NewEventSwitch()
 	eventSwitch.SetLogger(logger.With("module", "types"))
-	_, err := eventSwitch.Start()
-	if err != nil {
-		cmn.Exit(cmn.Fmt("Failed to start switch: %v", err))
+	if _, err := eventSwitch.Start(); err != nil {
+		return nil, fmt.Errorf("Failed to start switch: %v", err)
 	}
 
 	// Decide whether to fast-sync or not
@@ -119,13 +190,13 @@ func NewNode(config *cfg.Config, privValidator *types.PrivValidator, clientCreat
 	fastSync := config.FastSync
 	if state.Validators.Size() == 1 {
 		addr, _ := state.Validators.GetByIndex(0)
-		if bytes.Equal(privValidator.Address, addr) {
+		if bytes.Equal(privValidator.GetAddress(), addr) {
 			fastSync = false
 		}
 	}
 
 	// Log whether this node is a validator or an observer
-	if state.Validators.HasAddress(privValidator.Address) {
+	if state.Validators.HasAddress(privValidator.GetAddress()) {
 		consensusLogger.Info("This node is a validator")
 	} else {
 		consensusLogger.Info("This node is not a validator")
@@ -232,9 +303,10 @@ func NewNode(config *cfg.Config, privValidator *types.PrivValidator, clientCreat
 		txIndexer:        txIndexer,
 	}
 	node.BaseService = *cmn.NewBaseService(logger, "Node", node)
-	return node
+	return node, nil
 }
 
+// OnStart starts the Node. It implements cmn.Service.
 func (n *Node) OnStart() error {
 	// Create & add listener
 	protocol, address := ProtocolAndAddress(n.config.P2P.ListenAddress)
@@ -270,6 +342,7 @@ func (n *Node) OnStart() error {
 	return nil
 }
 
+// OnStop stops the Node. It implements cmn.Service.
 func (n *Node) OnStop() {
 	n.BaseService.OnStop()
 
@@ -285,6 +358,7 @@ func (n *Node) OnStop() {
 	}
 }
 
+// RunForever waits for an interupt signal and stops the node.
 func (n *Node) RunForever() {
 	// Sleep forever and then...
 	cmn.TrapSignal(func() {
@@ -292,15 +366,15 @@ func (n *Node) RunForever() {
 	})
 }
 
-// Add the event switch to reactors, mempool, etc.
+// SetEventSwitch adds the event switch to reactors, mempool, etc.
 func SetEventSwitch(evsw types.EventSwitch, eventables ...types.Eventable) {
 	for _, e := range eventables {
 		e.SetEventSwitch(evsw)
 	}
 }
 
-// Add a Listener to accept inbound peer connections.
-// Add listeners before starting the Node.
+// AddListener adds a listener to accept inbound peer connections.
+// It should be called before starting the Node.
 // The first listener is the primary listener (in NodeInfo)
 func (n *Node) AddListener(l p2p.Listener) {
 	n.sw.AddListener(l)
@@ -314,7 +388,7 @@ func (n *Node) ConfigureRPC() {
 	rpccore.SetConsensusState(n.consensusState)
 	rpccore.SetMempool(n.mempoolReactor.Mempool)
 	rpccore.SetSwitch(n.sw)
-	rpccore.SetPubKey(n.privValidator.PubKey)
+	rpccore.SetPubKey(n.privValidator.GetPubKey())
 	rpccore.SetGenesisDoc(n.genesisDoc)
 	rpccore.SetAddrBook(n.addrBook)
 	rpccore.SetProxyAppQuery(n.proxyApp.Query())
@@ -360,39 +434,48 @@ func (n *Node) startRPC() ([]net.Listener, error) {
 	return listeners, nil
 }
 
+// Switch returns the Node's Switch.
 func (n *Node) Switch() *p2p.Switch {
 	return n.sw
 }
 
+// BlockStore returns the Node's BlockStore.
 func (n *Node) BlockStore() *bc.BlockStore {
 	return n.blockStore
 }
 
+// ConsensusState returns the Node's ConsensusState.
 func (n *Node) ConsensusState() *consensus.ConsensusState {
 	return n.consensusState
 }
 
+// ConsensusReactor returns the Node's ConsensusReactor.
 func (n *Node) ConsensusReactor() *consensus.ConsensusReactor {
 	return n.consensusReactor
 }
 
+// MempoolReactor returns the Node's MempoolReactor.
 func (n *Node) MempoolReactor() *mempl.MempoolReactor {
 	return n.mempoolReactor
 }
 
+// EventSwitch returns the Node's EventSwitch.
 func (n *Node) EventSwitch() types.EventSwitch {
 	return n.evsw
 }
 
-// XXX: for convenience
-func (n *Node) PrivValidator() *types.PrivValidator {
+// PrivValidator returns the Node's PrivValidator.
+// XXX: for convenience only!
+func (n *Node) PrivValidator() types.PrivValidator {
 	return n.privValidator
 }
 
+// GenesisDoc returns the Node's GenesisDoc.
 func (n *Node) GenesisDoc() *types.GenesisDoc {
 	return n.genesisDoc
 }
 
+// ProxyApp returns the Node's AppConns, representing its connections to the ABCI application.
 func (n *Node) ProxyApp() proxy.AppConns {
 	return n.proxyApp
 }
@@ -442,15 +525,18 @@ func (n *Node) makeNodeInfo() *p2p.NodeInfo {
 
 //------------------------------------------------------------------------------
 
+// NodeInfo returns the Node's Info from the Switch.
 func (n *Node) NodeInfo() *p2p.NodeInfo {
 	return n.sw.NodeInfo()
 }
 
+// DialSeeds dials the given seeds on the Switch.
 func (n *Node) DialSeeds(seeds []string) error {
 	return n.sw.DialSeeds(n.addrBook, seeds)
 }
 
-// Defaults to tcp
+// ProtocolAndAddress returns the transport protocol
+// and the ip address from the given string. Defaults to tcp.
 func ProtocolAndAddress(listenAddr string) (string, string) {
 	protocol, address := "tcp", listenAddr
 	parts := strings.SplitN(address, "://", 2)
diff --git a/node/node_test.go b/node/node_test.go
index 3c751af6e..641e606c3 100644
--- a/node/node_test.go
+++ b/node/node_test.go
@@ -4,15 +4,19 @@ import (
 	"testing"
 	"time"
 
-	cfg "github.com/tendermint/tendermint/config"
+	"github.com/stretchr/testify/assert"
+
 	"github.com/tendermint/tmlibs/log"
+
+	cfg "github.com/tendermint/tendermint/config"
 )
 
 func TestNodeStartStop(t *testing.T) {
 	config := cfg.ResetTestRoot("node_node_test")
 
 	// Create & start node
-	n := NewNodeDefault(config, log.TestingLogger())
+	n, err := DefaultNewNode(config, log.TestingLogger())
+	assert.NoError(t, err, "expected no err on DefaultNewNode")
 	n.Start()
 	t.Logf("Started node %v", n.sw.NodeInfo())
 
diff --git a/rpc/test/helpers.go b/rpc/test/helpers.go
index 14da15c94..55e27f5b8 100644
--- a/rpc/test/helpers.go
+++ b/rpc/test/helpers.go
@@ -79,8 +79,13 @@ func NewTendermint(app abci.Application) *nm.Node {
 	logger := log.NewTMLogger(log.NewSyncWriter(os.Stdout))
 	logger = log.NewFilter(logger, log.AllowError())
 	privValidatorFile := config.PrivValidatorFile()
-	privValidator := types.LoadOrGenPrivValidator(privValidatorFile, logger)
+	privValidator := types.LoadOrGenPrivValidatorFS(privValidatorFile)
 	papp := proxy.NewLocalClientCreator(app)
-	node := nm.NewNode(config, privValidator, papp, logger)
+	node, err := nm.NewNode(config, privValidator, papp,
+		nm.DefaultGenesisDocProviderFunc(config),
+		nm.DefaultDBProvider, logger)
+	if err != nil {
+		panic(err)
+	}
 	return node
 }
diff --git a/state/execution_test.go b/state/execution_test.go
index 3ebc05d37..2987667c5 100644
--- a/state/execution_test.go
+++ b/state/execution_test.go
@@ -55,13 +55,14 @@ func makeTxs(blockNum int) (txs []types.Tx) {
 }
 
 func state() *State {
-	return MakeGenesisState(dbm.NewMemDB(), &types.GenesisDoc{
+	s, _ := MakeGenesisState(dbm.NewMemDB(), &types.GenesisDoc{
 		ChainID: chainID,
 		Validators: []types.GenesisValidator{
 			types.GenesisValidator{privKey.PubKey(), 10000, "test"},
 		},
 		AppHash: nil,
 	})
+	return s
 }
 
 func makeBlock(num int, state *State) *types.Block {
diff --git a/state/state.go b/state/state.go
index 2ebbec10e..53ec8cc03 100644
--- a/state/state.go
+++ b/state/state.go
@@ -68,14 +68,17 @@ type State struct {
 // GetState loads the most recent state from the database,
 // or creates a new one from the given genesisFile and persists the result
 // to the database.
-func GetState(stateDB dbm.DB, genesisFile string) *State {
+func GetState(stateDB dbm.DB, genesisFile string) (*State, error) {
+	var err error
 	state := LoadState(stateDB)
 	if state == nil {
-		state = MakeGenesisStateFromFile(stateDB, genesisFile)
+		state, err = MakeGenesisStateFromFile(stateDB, genesisFile)
+		if err != nil {
+			return nil, err
+		}
 		state.Save()
 	}
-
-	return state
+	return state, nil
 }
 
 // LoadState loads the State from the database.
@@ -316,25 +319,34 @@ func (vi *ValidatorsInfo) Bytes() []byte {
 // file.
 //
 // Used during replay and in tests.
-func MakeGenesisStateFromFile(db dbm.DB, genDocFile string) *State {
+func MakeGenesisStateFromFile(db dbm.DB, genDocFile string) (*State, error) {
+	genDoc, err := MakeGenesisDocFromFile(genDocFile)
+	if err != nil {
+		return nil, err
+	}
+	return MakeGenesisState(db, genDoc)
+}
+
+// MakeGenesisDocFromFile reads and unmarshals genesis doc from the given file.
+func MakeGenesisDocFromFile(genDocFile string) (*types.GenesisDoc, error) {
 	genDocJSON, err := ioutil.ReadFile(genDocFile)
 	if err != nil {
-		cmn.Exit(cmn.Fmt("Couldn't read GenesisDoc file: %v", err))
+		return nil, fmt.Errorf("Couldn't read GenesisDoc file: %v", err)
 	}
 	genDoc, err := types.GenesisDocFromJSON(genDocJSON)
 	if err != nil {
-		cmn.Exit(cmn.Fmt("Error reading GenesisDoc: %v", err))
+		return nil, fmt.Errorf("Error reading GenesisDoc: %v", err)
 	}
-	return MakeGenesisState(db, genDoc)
+	return genDoc, nil
 }
 
 // MakeGenesisState creates state from types.GenesisDoc.
 //
 // Used in tests.
-func MakeGenesisState(db dbm.DB, genDoc *types.GenesisDoc) *State {
+func MakeGenesisState(db dbm.DB, genDoc *types.GenesisDoc) (*State, error) {
 	err := genDoc.ValidateAndComplete()
 	if err != nil {
-		cmn.Exit(cmn.Fmt("Error in genesis file: %v", err))
+		return nil, fmt.Errorf("Error in genesis file: %v", err)
 	}
 
 	// Make validators slice
@@ -363,5 +375,5 @@ func MakeGenesisState(db dbm.DB, genDoc *types.GenesisDoc) *State {
 		AppHash:                     genDoc.AppHash,
 		TxIndexer:                   &null.TxIndex{}, // we do not need indexer during replay and in tests
 		LastHeightValidatorsChanged: 1,
-	}
+	}, nil
 }
diff --git a/state/state_test.go b/state/state_test.go
index 4ff367fa3..2c19a4164 100644
--- a/state/state_test.go
+++ b/state/state_test.go
@@ -23,7 +23,8 @@ import (
 func setupTestCase(t *testing.T) (func(t *testing.T), dbm.DB, *State) {
 	config := cfg.ResetTestRoot("state_")
 	stateDB := dbm.NewDB("state", config.DBBackend, config.DBDir())
-	state := GetState(stateDB, config.GenesisFile())
+	state, err := GetState(stateDB, config.GenesisFile())
+	assert.NoError(t, err, "expected no error on GetState")
 	state.SetLogger(log.TestingLogger())
 
 	tearDown := func(t *testing.T) {}
diff --git a/types/priv_validator.go b/types/priv_validator.go
index 3e84e7f36..8834eb7cc 100644
--- a/types/priv_validator.go
+++ b/types/priv_validator.go
@@ -11,8 +11,7 @@ import (
 
 	crypto "github.com/tendermint/go-crypto"
 	data "github.com/tendermint/go-wire/data"
-	. "github.com/tendermint/tmlibs/common"
-	"github.com/tendermint/tmlibs/log"
+	cmn "github.com/tendermint/tmlibs/common"
 )
 
 // TODO: type ?
@@ -30,12 +29,26 @@ func voteToStep(vote *Vote) int8 {
 	case VoteTypePrecommit:
 		return stepPrecommit
 	default:
-		PanicSanity("Unknown vote type")
+		cmn.PanicSanity("Unknown vote type")
 		return 0
 	}
 }
 
-type PrivValidator struct {
+// PrivValidator defines the functionality of a local Tendermint validator
+// that signs votes, proposals, and heartbeats, and never double signs.
+type PrivValidator interface {
+	GetAddress() data.Bytes // redundant since .PubKey().Address()
+	GetPubKey() crypto.PubKey
+
+	SignVote(chainID string, vote *Vote) error
+	SignProposal(chainID string, proposal *Proposal) error
+	SignHeartbeat(chainID string, heartbeat *Heartbeat) error
+}
+
+// PrivValidatorFS implements PrivValidator using data persisted to disk
+// to prevent double signing. The Signer itself can be mutated to use
+// something besides the default, for instance a hardware signer.
+type PrivValidatorFS struct {
 	Address       data.Bytes       `json:"address"`
 	PubKey        crypto.PubKey    `json:"pub_key"`
 	LastHeight    int              `json:"last_height"`
@@ -54,121 +67,124 @@ type PrivValidator struct {
 	mtx      sync.Mutex
 }
 
-// This is used to sign votes.
+// Signer is an interface that defines how to sign messages.
 // It is the caller's duty to verify the msg before calling Sign,
 // eg. to avoid double signing.
-// Currently, the only callers are SignVote and SignProposal
+// Currently, the only callers are SignVote, SignProposal, and SignHeartbeat.
 type Signer interface {
-	PubKey() crypto.PubKey
 	Sign(msg []byte) (crypto.Signature, error)
 }
 
-// Implements Signer
+// DefaultSigner implements Signer.
+// It uses a standard, unencrypted crypto.PrivKey.
 type DefaultSigner struct {
-	priv crypto.PrivKey
+	PrivKey crypto.PrivKey `json:"priv_key"`
 }
 
+// NewDefaultSigner returns an instance of DefaultSigner.
 func NewDefaultSigner(priv crypto.PrivKey) *DefaultSigner {
-	return &DefaultSigner{priv: priv}
+	return &DefaultSigner{
+		PrivKey: priv,
+	}
 }
 
-// Implements Signer
+// Sign implements Signer. It signs the byte slice with a private key.
 func (ds *DefaultSigner) Sign(msg []byte) (crypto.Signature, error) {
-	return ds.priv.Sign(msg), nil
+	return ds.PrivKey.Sign(msg), nil
 }
 
-// Implements Signer
-func (ds *DefaultSigner) PubKey() crypto.PubKey {
-	return ds.priv.PubKey()
+// GetAddress returns the address of the validator.
+// Implements PrivValidator.
+func (pv *PrivValidatorFS) GetAddress() data.Bytes {
+	return pv.Address
 }
 
-func (privVal *PrivValidator) SetSigner(s Signer) {
-	privVal.Signer = s
-	privVal.setPubKeyAndAddress()
+// GetPubKey returns the public key of the validator.
+// Implements PrivValidator.
+func (pv *PrivValidatorFS) GetPubKey() crypto.PubKey {
+	return pv.PubKey
 }
 
-// Overwrite address and pubkey for convenience
-func (privVal *PrivValidator) setPubKeyAndAddress() {
-	privVal.PubKey = privVal.Signer.PubKey()
-	privVal.Address = privVal.PubKey.Address()
-}
-
-// Generates a new validator with private key.
-func GenPrivValidator() *PrivValidator {
+// GenPrivValidatorFS generates a new validator with randomly generated private key
+// and sets the filePath, but does not call Save().
+func GenPrivValidatorFS(filePath string) *PrivValidatorFS {
 	privKey := crypto.GenPrivKeyEd25519().Wrap()
-	pubKey := privKey.PubKey()
-	return &PrivValidator{
-		Address:  pubKey.Address(),
-		PubKey:   pubKey,
+	return &PrivValidatorFS{
+		Address:  privKey.PubKey().Address(),
+		PubKey:   privKey.PubKey(),
 		PrivKey:  privKey,
 		LastStep: stepNone,
-		filePath: "",
 		Signer:   NewDefaultSigner(privKey),
+		filePath: filePath,
 	}
 }
 
-func LoadPrivValidator(filePath string) *PrivValidator {
+// LoadPrivValidatorFS loads a PrivValidatorFS from the filePath.
+func LoadPrivValidatorFS(filePath string) *PrivValidatorFS {
+	return LoadPrivValidatorFSWithSigner(filePath, func(privVal PrivValidator) Signer {
+		return NewDefaultSigner(privVal.(*PrivValidatorFS).PrivKey)
+	})
+}
+
+// LoadOrGenPrivValidatorFS loads a PrivValidatorFS from the given filePath
+// or else generates a new one and saves it to the filePath.
+func LoadOrGenPrivValidatorFS(filePath string) *PrivValidatorFS {
+	var privVal *PrivValidatorFS
+	if _, err := os.Stat(filePath); err == nil {
+		privVal = LoadPrivValidatorFS(filePath)
+	} else {
+		privVal = GenPrivValidatorFS(filePath)
+		privVal.Save()
+	}
+	return privVal
+}
+
+// LoadPrivValidatorWithSigner loads a PrivValidatorFS with a custom
+// signer object. The PrivValidatorFS handles double signing prevention by persisting
+// data to the filePath, while the Signer handles the signing.
+// If the filePath does not exist, the PrivValidatorFS must be created manually and saved.
+func LoadPrivValidatorFSWithSigner(filePath string, signerFunc func(PrivValidator) Signer) *PrivValidatorFS {
 	privValJSONBytes, err := ioutil.ReadFile(filePath)
 	if err != nil {
-		Exit(err.Error())
+		cmn.Exit(err.Error())
 	}
-	privVal := PrivValidator{}
+	privVal := &PrivValidatorFS{}
 	err = json.Unmarshal(privValJSONBytes, &privVal)
 	if err != nil {
-		Exit(Fmt("Error reading PrivValidator from %v: %v\n", filePath, err))
+		cmn.Exit(cmn.Fmt("Error reading PrivValidator from %v: %v\n", filePath, err))
 	}
 
 	privVal.filePath = filePath
-	privVal.Signer = NewDefaultSigner(privVal.PrivKey)
-	privVal.setPubKeyAndAddress()
-	return &privVal
+	privVal.Signer = signerFunc(privVal)
+	return privVal
 }
 
-func LoadOrGenPrivValidator(filePath string, logger log.Logger) *PrivValidator {
-	var privValidator *PrivValidator
-	if _, err := os.Stat(filePath); err == nil {
-		privValidator = LoadPrivValidator(filePath)
-		logger.Info("Loaded PrivValidator",
-			"file", filePath, "privValidator", privValidator)
-	} else {
-		privValidator = GenPrivValidator()
-		privValidator.SetFile(filePath)
-		privValidator.Save()
-		logger.Info("Generated PrivValidator", "file", filePath)
-	}
-	return privValidator
-}
-
-func (privVal *PrivValidator) SetFile(filePath string) {
-	privVal.mtx.Lock()
-	defer privVal.mtx.Unlock()
-	privVal.filePath = filePath
-}
-
-func (privVal *PrivValidator) Save() {
+// Save persists the PrivValidatorFS to disk.
+func (privVal *PrivValidatorFS) Save() {
 	privVal.mtx.Lock()
 	defer privVal.mtx.Unlock()
 	privVal.save()
 }
 
-func (privVal *PrivValidator) save() {
+func (privVal *PrivValidatorFS) save() {
 	if privVal.filePath == "" {
-		PanicSanity("Cannot save PrivValidator: filePath not set")
+		cmn.PanicSanity("Cannot save PrivValidator: filePath not set")
 	}
 	jsonBytes, err := json.Marshal(privVal)
 	if err != nil {
 		// `@; BOOM!!!
-		PanicCrisis(err)
+		cmn.PanicCrisis(err)
 	}
-	err = WriteFileAtomic(privVal.filePath, jsonBytes, 0600)
+	err = cmn.WriteFileAtomic(privVal.filePath, jsonBytes, 0600)
 	if err != nil {
 		// `@; BOOM!!!
-		PanicCrisis(err)
+		cmn.PanicCrisis(err)
 	}
 }
 
+// Reset resets all fields in the PrivValidatorFS.
 // NOTE: Unsafe!
-func (privVal *PrivValidator) Reset() {
+func (privVal *PrivValidatorFS) Reset() {
 	privVal.LastHeight = 0
 	privVal.LastRound = 0
 	privVal.LastStep = 0
@@ -177,22 +193,22 @@ func (privVal *PrivValidator) Reset() {
 	privVal.Save()
 }
 
-func (privVal *PrivValidator) GetAddress() []byte {
-	return privVal.Address
-}
-
-func (privVal *PrivValidator) SignVote(chainID string, vote *Vote) error {
+// SignVote signs a canonical representation of the vote, along with the chainID.
+// Implements PrivValidator.
+func (privVal *PrivValidatorFS) SignVote(chainID string, vote *Vote) error {
 	privVal.mtx.Lock()
 	defer privVal.mtx.Unlock()
 	signature, err := privVal.signBytesHRS(vote.Height, vote.Round, voteToStep(vote), SignBytes(chainID, vote))
 	if err != nil {
-		return errors.New(Fmt("Error signing vote: %v", err))
+		return errors.New(cmn.Fmt("Error signing vote: %v", err))
 	}
 	vote.Signature = signature
 	return nil
 }
 
-func (privVal *PrivValidator) SignProposal(chainID string, proposal *Proposal) error {
+// SignProposal signs a canonical representation of the proposal, along with the chainID.
+// Implements PrivValidator.
+func (privVal *PrivValidatorFS) SignProposal(chainID string, proposal *Proposal) error {
 	privVal.mtx.Lock()
 	defer privVal.mtx.Unlock()
 	signature, err := privVal.signBytesHRS(proposal.Height, proposal.Round, stepPropose, SignBytes(chainID, proposal))
@@ -203,8 +219,11 @@ func (privVal *PrivValidator) SignProposal(chainID string, proposal *Proposal) e
 	return nil
 }
 
-// check if there's a regression. Else sign and write the hrs+signature to disk
-func (privVal *PrivValidator) signBytesHRS(height, round int, step int8, signBytes []byte) (crypto.Signature, error) {
+// signBytesHRS signs the given signBytes if the height/round/step (HRS)
+// are greater than the latest state. If the HRS are equal,
+// it returns the privValidator.LastSignature.
+func (privVal *PrivValidatorFS) signBytesHRS(height, round int, step int8, signBytes []byte) (crypto.Signature, error) {
+
 	sig := crypto.Signature{}
 	// If height regression, err
 	if privVal.LastHeight > height {
@@ -223,7 +242,7 @@ func (privVal *PrivValidator) signBytesHRS(height, round int, step int8, signByt
 			} else if privVal.LastStep == step {
 				if privVal.LastSignBytes != nil {
 					if privVal.LastSignature.Empty() {
-						PanicSanity("privVal: LastSignature is nil but LastSignBytes is not!")
+						cmn.PanicSanity("privVal: LastSignature is nil but LastSignBytes is not!")
 					}
 					// so we dont sign a conflicting vote or proposal
 					// NOTE: proposals are non-deterministic (include time),
@@ -253,10 +272,11 @@ func (privVal *PrivValidator) signBytesHRS(height, round int, step int8, signByt
 	privVal.save()
 
 	return sig, nil
-
 }
 
-func (privVal *PrivValidator) SignHeartbeat(chainID string, heartbeat *Heartbeat) error {
+// SignHeartbeat signs a canonical representation of the heartbeat, along with the chainID.
+// Implements PrivValidator.
+func (privVal *PrivValidatorFS) SignHeartbeat(chainID string, heartbeat *Heartbeat) error {
 	privVal.mtx.Lock()
 	defer privVal.mtx.Unlock()
 	var err error
@@ -264,20 +284,21 @@ func (privVal *PrivValidator) SignHeartbeat(chainID string, heartbeat *Heartbeat
 	return err
 }
 
-func (privVal *PrivValidator) String() string {
-	return fmt.Sprintf("PrivValidator{%v LH:%v, LR:%v, LS:%v}", privVal.Address, privVal.LastHeight, privVal.LastRound, privVal.LastStep)
+// String returns a string representation of the PrivValidatorFS.
+func (privVal *PrivValidatorFS) String() string {
+	return fmt.Sprintf("PrivValidator{%v LH:%v, LR:%v, LS:%v}", privVal.GetAddress(), privVal.LastHeight, privVal.LastRound, privVal.LastStep)
 }
 
 //-------------------------------------
 
-type PrivValidatorsByAddress []*PrivValidator
+type PrivValidatorsByAddress []*PrivValidatorFS
 
 func (pvs PrivValidatorsByAddress) Len() int {
 	return len(pvs)
 }
 
 func (pvs PrivValidatorsByAddress) Less(i, j int) bool {
-	return bytes.Compare(pvs[i].Address, pvs[j].Address) == -1
+	return bytes.Compare(pvs[i].GetAddress(), pvs[j].GetAddress()) == -1
 }
 
 func (pvs PrivValidatorsByAddress) Swap(i, j int) {
diff --git a/types/priv_validator_test.go b/types/priv_validator_test.go
index 1eb0b57db..ac91de861 100644
--- a/types/priv_validator_test.go
+++ b/types/priv_validator_test.go
@@ -4,14 +4,44 @@ import (
 	"encoding/hex"
 	"encoding/json"
 	"fmt"
+	"os"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	crypto "github.com/tendermint/go-crypto"
+	"github.com/tendermint/go-wire/data"
+	cmn "github.com/tendermint/tmlibs/common"
 )
 
-func TestLoadValidator(t *testing.T) {
+func TestGenLoadValidator(t *testing.T) {
+	assert := assert.New(t)
+
+	_, tempFilePath := cmn.Tempfile("priv_validator_")
+	privVal := GenPrivValidatorFS(tempFilePath)
+
+	height := 100
+	privVal.LastHeight = height
+	privVal.Save()
+	addr := privVal.GetAddress()
+
+	privVal = LoadPrivValidatorFS(tempFilePath)
+	assert.Equal(addr, privVal.GetAddress(), "expected privval addr to be the same")
+	assert.Equal(height, privVal.LastHeight, "expected privval.LastHeight to have been saved")
+}
+
+func TestLoadOrGenValidator(t *testing.T) {
+	assert := assert.New(t)
+
+	_, tempFilePath := cmn.Tempfile("priv_validator_")
+	os.Remove(tempFilePath)
+	privVal := LoadOrGenPrivValidatorFS(tempFilePath)
+	addr := privVal.GetAddress()
+	privVal = LoadOrGenPrivValidatorFS(tempFilePath)
+	assert.Equal(addr, privVal.GetAddress(), "expected privval addr to be the same")
+}
+
+func TestUnmarshalValidator(t *testing.T) {
 	assert, require := assert.New(t), require.New(t)
 
 	// create some fixed values
@@ -34,23 +64,23 @@ func TestLoadValidator(t *testing.T) {
     "type": "ed25519",
     "data": "%s"
   },
-  "priv_key": {
-    "type": "ed25519",
-    "data": "%s"
-  },
   "last_height": 0,
   "last_round": 0,
   "last_step": 0,
-  "last_signature": null
+  "last_signature": null,
+  "priv_key": {
+    "type": "ed25519",
+    "data": "%s"
+  }
 }`, addrStr, pubStr, privStr)
 
-	val := PrivValidator{}
+	val := PrivValidatorFS{}
 	err = json.Unmarshal([]byte(serialized), &val)
 	require.Nil(err, "%+v", err)
 
 	// make sure the values match
-	assert.EqualValues(addrBytes, val.Address)
-	assert.EqualValues(pubKey, val.PubKey)
+	assert.EqualValues(addrBytes, val.GetAddress())
+	assert.EqualValues(pubKey, val.GetPubKey())
 	assert.EqualValues(privKey, val.PrivKey)
 
 	// export it and make sure it is the same
@@ -58,3 +88,89 @@ func TestLoadValidator(t *testing.T) {
 	require.Nil(err, "%+v", err)
 	assert.JSONEq(serialized, string(out))
 }
+
+func TestSignVote(t *testing.T) {
+	assert := assert.New(t)
+
+	_, tempFilePath := cmn.Tempfile("priv_validator_")
+	privVal := GenPrivValidatorFS(tempFilePath)
+
+	block1 := BlockID{[]byte{1, 2, 3}, PartSetHeader{}}
+	block2 := BlockID{[]byte{3, 2, 1}, PartSetHeader{}}
+	height, round := 10, 1
+	voteType := VoteTypePrevote
+
+	// sign a vote for first time
+	vote := newVote(privVal.Address, 0, height, round, voteType, block1)
+	err := privVal.SignVote("mychainid", vote)
+	assert.NoError(err, "expected no error signing vote")
+
+	// try to sign the same vote again; should be fine
+	err = privVal.SignVote("mychainid", vote)
+	assert.NoError(err, "expected no error on signing same vote")
+
+	// now try some bad votes
+	cases := []*Vote{
+		newVote(privVal.Address, 0, height, round-1, voteType, block1),   // round regression
+		newVote(privVal.Address, 0, height-1, round, voteType, block1),   // height regression
+		newVote(privVal.Address, 0, height-2, round+4, voteType, block1), // height regression and different round
+		newVote(privVal.Address, 0, height, round, voteType, block2),     // different block
+	}
+
+	for _, c := range cases {
+		err = privVal.SignVote("mychainid", c)
+		assert.Error(err, "expected error on signing conflicting vote")
+	}
+}
+
+func TestSignProposal(t *testing.T) {
+	assert := assert.New(t)
+
+	_, tempFilePath := cmn.Tempfile("priv_validator_")
+	privVal := GenPrivValidatorFS(tempFilePath)
+
+	block1 := PartSetHeader{5, []byte{1, 2, 3}}
+	block2 := PartSetHeader{10, []byte{3, 2, 1}}
+	height, round := 10, 1
+
+	// sign a proposal for first time
+	proposal := newProposal(height, round, block1)
+	err := privVal.SignProposal("mychainid", proposal)
+	assert.NoError(err, "expected no error signing proposal")
+
+	// try to sign the same proposal again; should be fine
+	err = privVal.SignProposal("mychainid", proposal)
+	assert.NoError(err, "expected no error on signing same proposal")
+
+	// now try some bad Proposals
+	cases := []*Proposal{
+		newProposal(height, round-1, block1),   // round regression
+		newProposal(height-1, round, block1),   // height regression
+		newProposal(height-2, round+4, block1), // height regression and different round
+		newProposal(height, round, block2),     // different block
+	}
+
+	for _, c := range cases {
+		err = privVal.SignProposal("mychainid", c)
+		assert.Error(err, "expected error on signing conflicting proposal")
+	}
+}
+
+func newVote(addr data.Bytes, idx, height, round int, typ byte, blockID BlockID) *Vote {
+	return &Vote{
+		ValidatorAddress: addr,
+		ValidatorIndex:   idx,
+		Height:           height,
+		Round:            round,
+		Type:             typ,
+		BlockID:          blockID,
+	}
+}
+
+func newProposal(height, round int, partsHeader PartSetHeader) *Proposal {
+	return &Proposal{
+		Height:           height,
+		Round:            round,
+		BlockPartsHeader: partsHeader,
+	}
+}
diff --git a/types/proposal_test.go b/types/proposal_test.go
index 6f6189595..d1c991849 100644
--- a/types/proposal_test.go
+++ b/types/proposal_test.go
@@ -28,17 +28,17 @@ func BenchmarkProposalWriteSignBytes(b *testing.B) {
 }
 
 func BenchmarkProposalSign(b *testing.B) {
-	privVal := GenPrivValidator()
+	privVal := GenPrivValidatorFS("")
 	for i := 0; i < b.N; i++ {
-		privVal.Sign(SignBytes("test_chain_id", testProposal))
+		privVal.Signer.Sign(SignBytes("test_chain_id", testProposal))
 	}
 }
 
 func BenchmarkProposalVerifySignature(b *testing.B) {
 	signBytes := SignBytes("test_chain_id", testProposal)
-	privVal := GenPrivValidator()
-	signature, _ := privVal.Sign(signBytes)
-	pubKey := privVal.PubKey
+	privVal := GenPrivValidatorFS("")
+	signature, _ := privVal.Signer.Sign(signBytes)
+	pubKey := privVal.GetPubKey()
 
 	for i := 0; i < b.N; i++ {
 		pubKey.VerifyBytes(SignBytes("test_chain_id", testProposal), signature)
diff --git a/types/validator.go b/types/validator.go
index 24f8974f3..506828913 100644
--- a/types/validator.go
+++ b/types/validator.go
@@ -106,14 +106,13 @@ func (vc validatorCodec) Compare(o1 interface{}, o2 interface{}) int {
 //--------------------------------------------------------------------------------
 // For testing...
 
-func RandValidator(randPower bool, minPower int64) (*Validator, *PrivValidator) {
-	privVal := GenPrivValidator()
+func RandValidator(randPower bool, minPower int64) (*Validator, *PrivValidatorFS) {
 	_, tempFilePath := cmn.Tempfile("priv_validator_")
-	privVal.SetFile(tempFilePath)
+	privVal := GenPrivValidatorFS(tempFilePath)
 	votePower := minPower
 	if randPower {
 		votePower += int64(cmn.RandUint32())
 	}
-	val := NewValidator(privVal.PubKey, votePower)
+	val := NewValidator(privVal.GetPubKey(), votePower)
 	return val, privVal
 }
diff --git a/types/validator_set.go b/types/validator_set.go
index e334ed9f3..1e9e3e314 100644
--- a/types/validator_set.go
+++ b/types/validator_set.go
@@ -369,9 +369,9 @@ func (ac accumComparable) Less(o interface{}) bool {
 // For testing
 
 // NOTE: PrivValidator are in order.
-func RandValidatorSet(numValidators int, votingPower int64) (*ValidatorSet, []*PrivValidator) {
+func RandValidatorSet(numValidators int, votingPower int64) (*ValidatorSet, []*PrivValidatorFS) {
 	vals := make([]*Validator, numValidators)
-	privValidators := make([]*PrivValidator, numValidators)
+	privValidators := make([]*PrivValidatorFS, numValidators)
 	for i := 0; i < numValidators; i++ {
 		val, privValidator := RandValidator(false, votingPower)
 		vals[i] = val
diff --git a/types/vote_set_test.go b/types/vote_set_test.go
index ddc055489..80ee6135c 100644
--- a/types/vote_set_test.go
+++ b/types/vote_set_test.go
@@ -11,7 +11,7 @@ import (
 )
 
 // NOTE: privValidators are in order
-func randVoteSet(height int, round int, type_ byte, numValidators int, votingPower int64) (*VoteSet, *ValidatorSet, []*PrivValidator) {
+func randVoteSet(height int, round int, type_ byte, numValidators int, votingPower int64) (*VoteSet, *ValidatorSet, []*PrivValidatorFS) {
 	valSet, privValidators := RandValidatorSet(numValidators, votingPower)
 	return NewVoteSet("test_chain_id", height, round, type_, valSet), valSet, privValidators
 }
@@ -59,9 +59,9 @@ func withBlockPartsHeader(vote *Vote, blockPartsHeader PartSetHeader) *Vote {
 	return vote
 }
 
-func signAddVote(privVal *PrivValidator, vote *Vote, voteSet *VoteSet) (bool, error) {
+func signAddVote(privVal *PrivValidatorFS, vote *Vote, voteSet *VoteSet) (bool, error) {
 	var err error
-	vote.Signature, err = privVal.Sign(SignBytes(voteSet.ChainID(), vote))
+	vote.Signature, err = privVal.Signer.Sign(SignBytes(voteSet.ChainID(), vote))
 	if err != nil {
 		return false, err
 	}
@@ -76,7 +76,7 @@ func TestAddVote(t *testing.T) {
 
 	// t.Logf(">> %v", voteSet)
 
-	if voteSet.GetByAddress(val0.Address) != nil {
+	if voteSet.GetByAddress(val0.GetAddress()) != nil {
 		t.Errorf("Expected GetByAddress(val0.Address) to be nil")
 	}
 	if voteSet.BitArray().GetIndex(0) {
@@ -88,7 +88,7 @@ func TestAddVote(t *testing.T) {
 	}
 
 	vote := &Vote{
-		ValidatorAddress: val0.Address,
+		ValidatorAddress: val0.GetAddress(),
 		ValidatorIndex:   0, // since privValidators are in order
 		Height:           height,
 		Round:            round,
@@ -100,7 +100,7 @@ func TestAddVote(t *testing.T) {
 		t.Error(err)
 	}
 
-	if voteSet.GetByAddress(val0.Address) == nil {
+	if voteSet.GetByAddress(val0.GetAddress()) == nil {
 		t.Errorf("Expected GetByAddress(val0.Address) to be present")
 	}
 	if !voteSet.BitArray().GetIndex(0) {
@@ -126,7 +126,7 @@ func Test2_3Majority(t *testing.T) {
 	}
 	// 6 out of 10 voted for nil.
 	for i := 0; i < 6; i++ {
-		vote := withValidator(voteProto, privValidators[i].Address, i)
+		vote := withValidator(voteProto, privValidators[i].GetAddress(), i)
 		signAddVote(privValidators[i], vote, voteSet)
 	}
 	blockID, ok := voteSet.TwoThirdsMajority()
@@ -136,7 +136,7 @@ func Test2_3Majority(t *testing.T) {
 
 	// 7th validator voted for some blockhash
 	{
-		vote := withValidator(voteProto, privValidators[6].Address, 6)
+		vote := withValidator(voteProto, privValidators[6].GetAddress(), 6)
 		signAddVote(privValidators[6], withBlockHash(vote, RandBytes(32)), voteSet)
 		blockID, ok = voteSet.TwoThirdsMajority()
 		if ok || !blockID.IsZero() {
@@ -146,7 +146,7 @@ func Test2_3Majority(t *testing.T) {
 
 	// 8th validator voted for nil.
 	{
-		vote := withValidator(voteProto, privValidators[7].Address, 7)
+		vote := withValidator(voteProto, privValidators[7].GetAddress(), 7)
 		signAddVote(privValidators[7], vote, voteSet)
 		blockID, ok = voteSet.TwoThirdsMajority()
 		if !ok || !blockID.IsZero() {
@@ -174,7 +174,7 @@ func Test2_3MajorityRedux(t *testing.T) {
 
 	// 66 out of 100 voted for nil.
 	for i := 0; i < 66; i++ {
-		vote := withValidator(voteProto, privValidators[i].Address, i)
+		vote := withValidator(voteProto, privValidators[i].GetAddress(), i)
 		signAddVote(privValidators[i], vote, voteSet)
 	}
 	blockID, ok := voteSet.TwoThirdsMajority()
@@ -184,7 +184,7 @@ func Test2_3MajorityRedux(t *testing.T) {
 
 	// 67th validator voted for nil
 	{
-		vote := withValidator(voteProto, privValidators[66].Address, 66)
+		vote := withValidator(voteProto, privValidators[66].GetAddress(), 66)
 		signAddVote(privValidators[66], withBlockHash(vote, nil), voteSet)
 		blockID, ok = voteSet.TwoThirdsMajority()
 		if ok || !blockID.IsZero() {
@@ -194,7 +194,7 @@ func Test2_3MajorityRedux(t *testing.T) {
 
 	// 68th validator voted for a different BlockParts PartSetHeader
 	{
-		vote := withValidator(voteProto, privValidators[67].Address, 67)
+		vote := withValidator(voteProto, privValidators[67].GetAddress(), 67)
 		blockPartsHeader := PartSetHeader{blockPartsTotal, crypto.CRandBytes(32)}
 		signAddVote(privValidators[67], withBlockPartsHeader(vote, blockPartsHeader), voteSet)
 		blockID, ok = voteSet.TwoThirdsMajority()
@@ -205,7 +205,7 @@ func Test2_3MajorityRedux(t *testing.T) {
 
 	// 69th validator voted for different BlockParts Total
 	{
-		vote := withValidator(voteProto, privValidators[68].Address, 68)
+		vote := withValidator(voteProto, privValidators[68].GetAddress(), 68)
 		blockPartsHeader := PartSetHeader{blockPartsTotal + 1, blockPartsHeader.Hash}
 		signAddVote(privValidators[68], withBlockPartsHeader(vote, blockPartsHeader), voteSet)
 		blockID, ok = voteSet.TwoThirdsMajority()
@@ -216,7 +216,7 @@ func Test2_3MajorityRedux(t *testing.T) {
 
 	// 70th validator voted for different BlockHash
 	{
-		vote := withValidator(voteProto, privValidators[69].Address, 69)
+		vote := withValidator(voteProto, privValidators[69].GetAddress(), 69)
 		signAddVote(privValidators[69], withBlockHash(vote, RandBytes(32)), voteSet)
 		blockID, ok = voteSet.TwoThirdsMajority()
 		if ok || !blockID.IsZero() {
@@ -226,7 +226,7 @@ func Test2_3MajorityRedux(t *testing.T) {
 
 	// 71st validator voted for the right BlockHash & BlockPartsHeader
 	{
-		vote := withValidator(voteProto, privValidators[70].Address, 70)
+		vote := withValidator(voteProto, privValidators[70].GetAddress(), 70)
 		signAddVote(privValidators[70], vote, voteSet)
 		blockID, ok = voteSet.TwoThirdsMajority()
 		if !ok || !blockID.Equals(BlockID{blockHash, blockPartsHeader}) {
@@ -250,7 +250,7 @@ func TestBadVotes(t *testing.T) {
 
 	// val0 votes for nil.
 	{
-		vote := withValidator(voteProto, privValidators[0].Address, 0)
+		vote := withValidator(voteProto, privValidators[0].GetAddress(), 0)
 		added, err := signAddVote(privValidators[0], vote, voteSet)
 		if !added || err != nil {
 			t.Errorf("Expected VoteSet.Add to succeed")
@@ -259,7 +259,7 @@ func TestBadVotes(t *testing.T) {
 
 	// val0 votes again for some block.
 	{
-		vote := withValidator(voteProto, privValidators[0].Address, 0)
+		vote := withValidator(voteProto, privValidators[0].GetAddress(), 0)
 		added, err := signAddVote(privValidators[0], withBlockHash(vote, RandBytes(32)), voteSet)
 		if added || err == nil {
 			t.Errorf("Expected VoteSet.Add to fail, conflicting vote.")
@@ -268,7 +268,7 @@ func TestBadVotes(t *testing.T) {
 
 	// val1 votes on another height
 	{
-		vote := withValidator(voteProto, privValidators[1].Address, 1)
+		vote := withValidator(voteProto, privValidators[1].GetAddress(), 1)
 		added, err := signAddVote(privValidators[1], withHeight(vote, height+1), voteSet)
 		if added || err == nil {
 			t.Errorf("Expected VoteSet.Add to fail, wrong height")
@@ -277,7 +277,7 @@ func TestBadVotes(t *testing.T) {
 
 	// val2 votes on another round
 	{
-		vote := withValidator(voteProto, privValidators[2].Address, 2)
+		vote := withValidator(voteProto, privValidators[2].GetAddress(), 2)
 		added, err := signAddVote(privValidators[2], withRound(vote, round+1), voteSet)
 		if added || err == nil {
 			t.Errorf("Expected VoteSet.Add to fail, wrong round")
@@ -286,7 +286,7 @@ func TestBadVotes(t *testing.T) {
 
 	// val3 votes of another type.
 	{
-		vote := withValidator(voteProto, privValidators[3].Address, 3)
+		vote := withValidator(voteProto, privValidators[3].GetAddress(), 3)
 		added, err := signAddVote(privValidators[3], withType(vote, VoteTypePrecommit), voteSet)
 		if added || err == nil {
 			t.Errorf("Expected VoteSet.Add to fail, wrong type")
@@ -311,7 +311,7 @@ func TestConflicts(t *testing.T) {
 
 	// val0 votes for nil.
 	{
-		vote := withValidator(voteProto, privValidators[0].Address, 0)
+		vote := withValidator(voteProto, privValidators[0].GetAddress(), 0)
 		added, err := signAddVote(privValidators[0], vote, voteSet)
 		if !added || err != nil {
 			t.Errorf("Expected VoteSet.Add to succeed")
@@ -320,7 +320,7 @@ func TestConflicts(t *testing.T) {
 
 	// val0 votes again for blockHash1.
 	{
-		vote := withValidator(voteProto, privValidators[0].Address, 0)
+		vote := withValidator(voteProto, privValidators[0].GetAddress(), 0)
 		added, err := signAddVote(privValidators[0], withBlockHash(vote, blockHash1), voteSet)
 		if added {
 			t.Errorf("Expected VoteSet.Add to fail, conflicting vote.")
@@ -335,7 +335,7 @@ func TestConflicts(t *testing.T) {
 
 	// val0 votes again for blockHash1.
 	{
-		vote := withValidator(voteProto, privValidators[0].Address, 0)
+		vote := withValidator(voteProto, privValidators[0].GetAddress(), 0)
 		added, err := signAddVote(privValidators[0], withBlockHash(vote, blockHash1), voteSet)
 		if !added {
 			t.Errorf("Expected VoteSet.Add to succeed, called SetPeerMaj23().")
@@ -350,7 +350,7 @@ func TestConflicts(t *testing.T) {
 
 	// val0 votes again for blockHash1.
 	{
-		vote := withValidator(voteProto, privValidators[0].Address, 0)
+		vote := withValidator(voteProto, privValidators[0].GetAddress(), 0)
 		added, err := signAddVote(privValidators[0], withBlockHash(vote, blockHash2), voteSet)
 		if added {
 			t.Errorf("Expected VoteSet.Add to fail, duplicate SetPeerMaj23() from peerA")
@@ -362,7 +362,7 @@ func TestConflicts(t *testing.T) {
 
 	// val1 votes for blockHash1.
 	{
-		vote := withValidator(voteProto, privValidators[1].Address, 1)
+		vote := withValidator(voteProto, privValidators[1].GetAddress(), 1)
 		added, err := signAddVote(privValidators[1], withBlockHash(vote, blockHash1), voteSet)
 		if !added || err != nil {
 			t.Errorf("Expected VoteSet.Add to succeed")
@@ -379,7 +379,7 @@ func TestConflicts(t *testing.T) {
 
 	// val2 votes for blockHash2.
 	{
-		vote := withValidator(voteProto, privValidators[2].Address, 2)
+		vote := withValidator(voteProto, privValidators[2].GetAddress(), 2)
 		added, err := signAddVote(privValidators[2], withBlockHash(vote, blockHash2), voteSet)
 		if !added || err != nil {
 			t.Errorf("Expected VoteSet.Add to succeed")
@@ -399,7 +399,7 @@ func TestConflicts(t *testing.T) {
 
 	// val2 votes for blockHash1.
 	{
-		vote := withValidator(voteProto, privValidators[2].Address, 2)
+		vote := withValidator(voteProto, privValidators[2].GetAddress(), 2)
 		added, err := signAddVote(privValidators[2], withBlockHash(vote, blockHash1), voteSet)
 		if !added {
 			t.Errorf("Expected VoteSet.Add to succeed")
@@ -439,7 +439,7 @@ func TestMakeCommit(t *testing.T) {
 
 	// 6 out of 10 voted for some block.
 	for i := 0; i < 6; i++ {
-		vote := withValidator(voteProto, privValidators[i].Address, i)
+		vote := withValidator(voteProto, privValidators[i].GetAddress(), i)
 		signAddVote(privValidators[i], vote, voteSet)
 	}
 
@@ -448,7 +448,7 @@ func TestMakeCommit(t *testing.T) {
 
 	// 7th voted for some other block.
 	{
-		vote := withValidator(voteProto, privValidators[6].Address, 6)
+		vote := withValidator(voteProto, privValidators[6].GetAddress(), 6)
 		vote = withBlockHash(vote, RandBytes(32))
 		vote = withBlockPartsHeader(vote, PartSetHeader{123, RandBytes(32)})
 		signAddVote(privValidators[6], vote, voteSet)
@@ -456,7 +456,7 @@ func TestMakeCommit(t *testing.T) {
 
 	// The 8th voted like everyone else.
 	{
-		vote := withValidator(voteProto, privValidators[7].Address, 7)
+		vote := withValidator(voteProto, privValidators[7].GetAddress(), 7)
 		signAddVote(privValidators[7], vote, voteSet)
 	}