diff --git a/go.mod b/go.mod
index 2573f8e..71f50f1 100644
--- a/go.mod
+++ b/go.mod
@@ -2,7 +2,4 @@ module filippo.io/age
 
 go 1.13
 
-require (
-	github.com/sergi/go-diff v1.1.0
-	golang.org/x/crypto v0.0.0-20200323165209-0ec3e9974c59
-)
+require golang.org/x/crypto v0.0.0-20200323165209-0ec3e9974c59
diff --git a/go.sum b/go.sum
index 89822ea..112faf0 100644
--- a/go.sum
+++ b/go.sum
@@ -1,18 +1,3 @@
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
-github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
-github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
-github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
-github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
-github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
-github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
-github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/sergi/go-diff v1.1.0 h1:we8PVUC3FE2uYfodKH/nBHMSetSfHDR6scGdBi+erh0=
-github.com/sergi/go-diff v1.1.0/go.mod h1:STckp+ISIX8hZLjrqAeVduY0gWCT9IjLuqbuNXdaHfM=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
-github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20200323165209-0ec3e9974c59 h1:3zb4D3T4G8jdExgVU/95+vQXfpEPiMdCaZgmGVxjNHM=
 golang.org/x/crypto v0.0.0-20200323165209-0ec3e9974c59/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
@@ -21,9 +6,3 @@ golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5h
 golang.org/x/sys v0.0.0-20190412213103-97732733099d h1:+R4KGOnez64A81RvjARKc4UT5/tI9ujCIVX+P5KiHuI=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
-gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v2 v2.2.4 h1:/eiJrUcujPVeJ3xlSWaiNi3uSVmDGBK1pDHUHAnao1I=
-gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
diff --git a/internal/format/Dockerfile.go-fuzz b/internal/format/Dockerfile.go-fuzz
deleted file mode 100644
index 589e510..0000000
--- a/internal/format/Dockerfile.go-fuzz
+++ /dev/null
@@ -1,21 +0,0 @@
-# Copyright 2019 Google LLC
-#
-# Use of this source code is governed by a BSD-style
-# license that can be found in the LICENSE file or at
-# https://developers.google.com/open-source/licenses/bsd
-
-# docker run --rm -v $PWD/workdir:/workdir $(docker build -q -f internal/format/Dockerfile.go-fuzz .)
-
-FROM golang:1.14-alpine3.11
-
-RUN apk add --no-cache git
-RUN go get github.com/dvyukov/go-fuzz/...
-
-ADD . $GOPATH/src/filippo.io/age/
-WORKDIR $GOPATH/src/filippo.io/age
-
-RUN go-fuzz-build ./internal/format
-
-VOLUME /workdir
-
-ENTRYPOINT ["go-fuzz", "-workdir", "/workdir", "-bin", "format-fuzz.zip"]
diff --git a/internal/format/format_gofuzz.go b/internal/format/format_gofuzz.go
deleted file mode 100644
index 674f8eb..0000000
--- a/internal/format/format_gofuzz.go
+++ /dev/null
@@ -1,60 +0,0 @@
-// Copyright 2019 Google LLC
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file or at
-// https://developers.google.com/open-source/licenses/bsd
-
-// +build gofuzz
-
-package format
-
-import (
-	"bytes"
-	"fmt"
-	"io"
-	"strings"
-
-	"github.com/sergi/go-diff/diffmatchpatch"
-)
-
-func Fuzz(data []byte) int {
-	isArmored := bytes.HasPrefix(data, []byte("-----BEGIN AGE ENCRYPTED FILE-----"))
-	h, payload, err := Parse(bytes.NewReader(data))
-	if err != nil {
-		if h != nil {
-			panic("h != nil on error")
-		}
-		if payload != nil {
-			panic("payload != nil on error")
-		}
-		return 0
-	}
-	w := &bytes.Buffer{}
-	if isArmored {
-		w := ArmoredWriter(w)
-		if err := h.Marshal(w); err != nil {
-			panic(err)
-		}
-		if _, err := io.Copy(w, payload); err != nil {
-			if strings.Contains(err.Error(), "invalid armor") {
-				return 0
-			}
-			panic(err)
-		}
-		w.Close()
-	} else {
-		if err := h.Marshal(w); err != nil {
-			panic(err)
-		}
-		if _, err := io.Copy(w, payload); err != nil {
-			panic(err)
-		}
-	}
-	if !bytes.Equal(w.Bytes(), data) {
-		dmp := diffmatchpatch.New()
-		diffs := dmp.DiffMain(string(data), string(w.Bytes()), false)
-		fmt.Println(dmp.DiffToDelta(diffs))
-		panic("Marshal output different from input")
-	}
-	return 1
-}