Using 96 bit of random data and a 32 bit counter (as specified in https://tools.ietf.org/html/rfc3686#section-4). Thus maximum file size supported by Cryptomator is 64GiB, but decreasing risk of IV collisions to 1 : 2^48

main/crypto-api/src/main/java/org/cryptomator/crypto/Cryptor.java

@@ -16,6 +16,7 @@ import java.nio.file.DirectoryStream.Filter;
 import java.nio.file.Path;
 
 import org.cryptomator.crypto.exceptions.DecryptFailedException;
+import org.cryptomator.crypto.exceptions.EncryptFailedException;
 import org.cryptomator.crypto.exceptions.UnsupportedKeyLengthException;
 import org.cryptomator.crypto.exceptions.WrongPasswordException;
 
@@ -97,7 +98,7 @@ public interface Cryptor extends SensitiveDataSwipeListener {
 	/**
 	 * @return Number of encrypted bytes. This might not be equal to the encrypted file size due to optional metadata written to it.
 	 */
-	Long encryptFile(InputStream plaintextFile, SeekableByteChannel encryptedFile) throws IOException;
+	Long encryptFile(InputStream plaintextFile, SeekableByteChannel encryptedFile) throws IOException, EncryptFailedException;
 
 	/**
 	 * @return A filter, that returns <code>true</code> for encrypted files, i.e. if the file is an actual user payload and not a supporting

main/crypto-api/src/main/java/org/cryptomator/crypto/SamplingDecorator.java

@@ -10,6 +10,7 @@ import java.util.concurrent.atomic.AtomicLong;
 
 import org.apache.commons.lang3.StringUtils;
 import org.cryptomator.crypto.exceptions.DecryptFailedException;
+import org.cryptomator.crypto.exceptions.EncryptFailedException;
 import org.cryptomator.crypto.exceptions.UnsupportedKeyLengthException;
 import org.cryptomator.crypto.exceptions.WrongPasswordException;
 
@@ -99,7 +100,7 @@ public class SamplingDecorator implements Cryptor, CryptorIOSampling {
 	}
 
 	@Override
-	public Long encryptFile(InputStream plaintextFile, SeekableByteChannel encryptedFile) throws IOException {
+	public Long encryptFile(InputStream plaintextFile, SeekableByteChannel encryptedFile) throws IOException, EncryptFailedException {
 		final InputStream countingInputStream = new CountingInputStream(encryptedBytes, plaintextFile);
 		return cryptor.encryptFile(countingInputStream, encryptedFile);
 	}

main/crypto-api/src/main/java/org/cryptomator/crypto/exceptions/CounterOverflowException.java

@@ -0,0 +1,10 @@
+package org.cryptomator.crypto.exceptions;
+
+public class CounterOverflowException extends EncryptFailedException {
+	private static final long serialVersionUID = 380066751064534731L;
+
+	public CounterOverflowException(String msg) {
+		super(msg);
+	}
+
+}

main/crypto-api/src/main/java/org/cryptomator/crypto/exceptions/EncryptFailedException.java

@@ -0,0 +1,9 @@
+package org.cryptomator.crypto.exceptions;
+
+public class EncryptFailedException extends StorageCryptingException {
+	private static final long serialVersionUID = -3855673600374897828L;
+
+	public EncryptFailedException(String msg) {
+		super(msg);
+	}
+}