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javax.crypto.BadPaddingException: pad block corrupted sometimes

I have the following code for encrypt
public static String encrypt(String value, char[] secret) {
try {
final byte[] bytes = value != null ? value.getBytes(StandardCharsets.UTF_8) : new byte[0];
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
SecretKey key = keyFactory.generateSecret(new PBEKeySpec(secret));
Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
pbeCipher.init(Cipher.ENCRYPT_MODE, key, new PBEParameterSpec(IsoGame.$().crossPlatformManager.getCrossPlatformUtilsInstance().getDeviceUniqueIdentifier().getBytes(StandardCharsets.UTF_8), 20));
return new String(Base64.encodeBase64(pbeCipher.doFinal(bytes)), StandardCharsets.UTF_8);
} catch (Exception e) {
e.printStackTrace();
}
return value;
}
and the following code for decrypt.
public static String decrypt(String value, char[] secret) {
try {
final byte[] bytes = value != null ? Base64.decodeBase64(value.getBytes(StandardCharsets.UTF_8)) : new byte[0];
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
SecretKey key = keyFactory.generateSecret(new PBEKeySpec(secret));
Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
pbeCipher.init(Cipher.DECRYPT_MODE, key, new PBEParameterSpec(IsoGame.$().crossPlatformManager.getCrossPlatformUtilsInstance().getDeviceUniqueIdentifier().getBytes(StandardCharsets.UTF_8), 20));
return new String(pbeCipher.doFinal(bytes), StandardCharsets.UTF_8);
} catch (Exception e) {
e.printStackTrace();
}
return value;
}
However, sometimes the exception is being thrown at
pbeCipher.doFinal(bytes)
in decrypt method.
The exception is javax.crypto.BadPaddingException: pad block corrupted
It's strange, as I'm getting this exception sometimes with the same values .
Any ideas?
Thanks.

The most likely reason would simply be the wrong password to be supplied. If the wrong password is supplied then the wrong key is derived. Then the ciphertext will be decrypted to garbage plaintext. This will only be noticed if the padding exception gets thrown: unpadding random bytes is likely to fail.
You could e.g. first validate that the derived key is correct by performing a HMAC over known data using the derived key. In addition, it would be a good idea to use some kind of authenticated encryption, so that if the key or data is wrong or corrupted that decryption does indeed fail. If you're unlucky then - at this time - the data will decrypt, unpadding will succeed and you end up with garbage plaintext.
Of course, you'd better upgrade to PBKDF2 for key derivation, and upgrade AES to e.g. AES-GCM instead of DES. Currently your encryption is entirely insecure, even if you use a strong password.

Your problem is
IsoGame.$().crossPlatformManager.getCrossPlatformUtilsInstance().getDeviceUniqueIdentifier().getBytes(StandardCharsets.UTF_8)
I have ran the following code multiple times and no exception occurred and the decrypted data was equal to "Hello there!":
public static void main(String[] args)
{
new CryptographyError();
}
private CryptographyError()
{
char[] secret = "MySecret".toCharArray();
String mesasge = "Hello there!";
EncryptedData encryptedData = encrypt(mesasge, secret);
System.out.println("ENCRYPTED " + encryptedData.encryptedString);
String decrypted = decrypt(encryptedData, secret);
System.out.println("DECRYPTED " + decrypted);
}
private static final SecureRandom RANDOM = new SecureRandom();
public static EncryptedData encrypt(String value, char[] secret) {
try {
final byte[] bytes = value != null ? value.getBytes(StandardCharsets.UTF_8) : new byte[0];
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
SecretKey key = keyFactory.generateSecret(new PBEKeySpec(secret));
Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
byte[] salt = new byte[8];
RANDOM.nextBytes(salt);
pbeCipher.init(Cipher.ENCRYPT_MODE, key, new PBEParameterSpec(salt, 20));
return new EncryptedData(salt, new String(Base64.getEncoder().encode(pbeCipher.doFinal(bytes)), StandardCharsets.UTF_8));
} catch (Exception e) {
e.printStackTrace();
System.out.println(value);
}
return null;
}
public static String decrypt(EncryptedData encryptedData, char[] secret) {
try {
String value = encryptedData.encryptedString;
byte[] salt = encryptedData.salt;
final byte[] bytes = value != null ? Base64.getDecoder().decode(value.getBytes(StandardCharsets.UTF_8)) : new byte[0];
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
SecretKey key = keyFactory.generateSecret(new PBEKeySpec(secret));
Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
pbeCipher.init(Cipher.DECRYPT_MODE, key, new PBEParameterSpec(salt, 20));
return new String(pbeCipher.doFinal(bytes), StandardCharsets.UTF_8);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
private static class EncryptedData
{
private final byte[] salt;
private final String encryptedString;
private EncryptedData(byte[] salt, String encryptedString)
{
this.salt = salt;
this.encryptedString = encryptedString;
}
}
The only main difference between my code and your code is
IsoGame.$().crossPlatformManager.getCrossPlatformUtilsInstance().getDeviceUniqueIdentifier().getBytes(StandardCharsets.UTF_8)
which means that must not return the same value on encryption and decryption.
Also if you want to test this you can just change the salt between them and notice the exception is thrown again.
Also Maarten Bodewes gave you some good notes about how to improve your code.

how to convert a string in to a byte array

I've wrote a method to encrypt/decrypt a string. Encryption is happening successfully but I cannot manage to make the decryption work... This is the code I have written:
public String encrypt(String a, int x) {
String ret = "";
String text = a;
String key = "Bar12345Bar12345"; // 128 bit key
try {
// Create key and cipher
Key aesKey = new SecretKeySpec(key.getBytes(), "AES");
Cipher cipher = Cipher.getInstance("AES");
if(x == 0) { //x==0 means I want to encrypt
// encrypt the text
cipher.init(Cipher.ENCRYPT_MODE, aesKey);
byte[] encrypted = cipher.doFinal(text.getBytes());
ret =new String(encrypted);
}
else { //if not 0 I want to decrypt
// decrypt the text
byte[] encrypted = text.getBytes(Charset.forName("UTF-8"));
cipher.init(Cipher.DECRYPT_MODE, aesKey);
String decrypted = new String(cipher.doFinal(encrypted));
ret=decrypted;
}
} catch(Exception e) {
e.printStackTrace();
}
return ret;
}
I think the problem arise when I'm trying to convert the string into byte array. The error I get is:
javax.crypto.BadPaddingException: Given final block not properly padded
So what is the problem ? If I am not converting the string into byte array in right way, how should I do it ?

AES encryption, got extra trash characters in decrypted file

Im making a debug loggin function in an android app.
I have a simple class which is logging to .txt file using 128 bit AES encryption.
After the logging is done, i decrypt the logged file with a simple JAVA program.
The problem is when i decrypt the encrypted log i got some weird content in it, i also got the encrypted content, but there are some extra characters, see below.
Android app logging part:
public class FileLogger {
//file and folder name
public static String LOG_FILE_NAME = "my_log.txt";
public static String LOG_FOLDER_NAME = "my_log_folder";
static SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd_HH-mm-ss_SSS");
//My secret key, 16 bytes = 128 bit
static byte[] key = {1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6};
//Appends to a log file, using encryption
public static void appendToLog(Context context, Object msg) {
String msgStr;
String timestamp = "t:" + formatter.format(new java.util.Date());
msgStr = msg + "|" + timestamp + "\n";
File sdcard = Environment.getExternalStorageDirectory();
File dir = new File(sdcard.getAbsolutePath() + "/" + LOG_FOLDER_NAME);
if (!dir.exists()) {
dir.mkdir();
}
File encryptedFile = new File(dir, LOG_FILE_NAME);
try {
//Encryption using my key above defined
Key secretKey = new SecretKeySpec(key, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
byte[] outputBytes = cipher.doFinal(msgStr.getBytes());
//Writing to the file using append mode
FileOutputStream outputStream = new FileOutputStream(encryptedFile, true);
outputStream.write(outputBytes);
outputStream.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (NoSuchPaddingException e) {
e.printStackTrace();
} catch (IllegalBlockSizeException e) {
e.printStackTrace();
} catch (BadPaddingException e) {
e.printStackTrace();
} catch (InvalidKeyException e) {
e.printStackTrace();
}
}
}
And this is the decrypter JAVA program:
public class Main {
//output file name after decryption
private static String decryptedFileName;
//input encrypted file
private static String fileSource;
//a prefix tag for output file name
private static String outputFilePrefix = "decrypted_";
//My key for decryption, its the same as in the encrypter program.
static byte[] key = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6 };
//Decrypting function
public static void decrypt(byte[] key, File inputFile, File outputFile) throws Exception {
try {
Key secretKey = new SecretKeySpec(key, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.DECRYPT_MODE, secretKey);
FileInputStream inputStream = new FileInputStream(inputFile);
byte[] inputBytes = new byte[(int) inputFile.length()];
inputStream.read(inputBytes);
byte[] outputBytes = cipher.doFinal(inputBytes);
FileOutputStream outputStream = new FileOutputStream(outputFile, true);
outputStream.write(outputBytes);
inputStream.close();
outputStream.close();
} catch (Exception ex) {
ex.printStackTrace();
}
}
//first argument is the intput file source
public static void main(String[] args) {
if (args.length != 1) {
System.out.println("Add log file name as a parameter.");
} else {
fileSource = args[0];
try {
File sourceFile = new File(fileSource);
if (sourceFile.exists()) {
//Decrption
decryptedFileName = outputFilePrefix + sourceFile.getName();
File decryptedFile = new File(decryptedFileName);
decrypt(key, sourceFile, decryptedFile);
} else {
System.out.println("Log file not found: " + fileSource);
}
} catch (Exception e) {
e.printStackTrace();
}
System.out.println("Decryption done, output file: " + decryptedFileName);
}
}
}
Output decrypted log (Opened with notepad++):
There is the valid content, but you also can see the extra thrash characters. If I open with the default windows text editor i also got thrash charaters, but different ones.
This is my first try with encrypt -decrypt, what m i doing wrong?
Any ideas?

AES is a block cipher which only works on blocks. The plaintext that you want to encrypt can be of any length, so the cipher must always pad the plaintext to fill it up to a multiple of the block size (or add a complete block when it already is a multiple of the block size). In this PKCS#5/PKCS#7 padding each padding byte denotes the number of padded bytes.
The easy fix would be to iterate over outputBytes during decryption and remove those padding bytes which are always on the next line. This will break as soon as you use multiline log messages or use a semantically secure mode (more on that later).
The better fix would be to write the number of bytes for each log message before the message, read that and decrypt only that many bytes. This also probably easier to implement with file streams.
You currently use Cipher.getInstance("AES"); which is a non-fully qualified version of Cipher.getInstance("AES/ECB/PKCS5Padding");. ECB mode is not semantically secure. It simply encrypts each block (16 bytes) with AES and the key. So blocks that are the same will be the same in ciphertext. This is particularly bad, because some log messages start the same and an attacker might be able to distinguish them. This is also the reason why the decryption of the whole file worked despite being encrypted in chunks. You should use CBC mode with a random IV.
Here is some sample code for proper use of AES in CBC mode with a random IV using streams:
private static SecretKey key = generateAESkey();
private static String cipherString = "AES/CBC/PKCS5Padding";
public static void main(String[] args) throws Exception {
ByteArrayOutputStream log = new ByteArrayOutputStream();
appendToLog("Test1", log);
appendToLog("Test2 is longer", log);
appendToLog("Test3 is multiple of block size!", log);
appendToLog("Test4 is shorter.", log);
byte[] encLog = log.toByteArray();
List<String> logs = decryptLog(new ByteArrayInputStream(encLog));
for(String logLine : logs) {
System.out.println(logLine);
}
}
private static SecretKey generateAESkey() {
try {
return KeyGenerator.getInstance("AES").generateKey();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
}
return null;
}
private static byte[] generateIV() {
SecureRandom random = new SecureRandom();
byte[] iv = new byte[16];
random.nextBytes(iv);
return iv;
}
public static void appendToLog(String s, OutputStream os) throws Exception {
Cipher cipher = Cipher.getInstance(cipherString);
byte[] iv = generateIV();
cipher.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(iv));
byte[] data = cipher.doFinal(s.getBytes("UTF-8"));
os.write(data.length);
os.write(iv);
os.write(data);
}
public static List<String> decryptLog(InputStream is) throws Exception{
ArrayList<String> logs = new ArrayList<String>();
while(is.available() > 0) {
int len = is.read();
byte[] encLogLine = new byte[len];
byte[] iv = new byte[16];
is.read(iv);
is.read(encLogLine);
Cipher cipher = Cipher.getInstance(cipherString);
cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(iv));
byte[] data = cipher.doFinal(encLogLine);
logs.add(new String(data, "UTF-8"));
}
return logs;
}

You've encrypted each log message with a distinct encryption context. When you call the doFinal method on the cipher object the plaintext is padded out to a multiple of 16. Effectively, your log file is sequence of many small encrypted messages. However on decryption you are ignoring these message boundaries and treating the file as a single encrypted message. The result is that the padding characters are not being properly stripped. What you are seeing as 'trash' characters are likely these padding bytes. You will need to redesign your logfile format, either to preserve the message boundaries so the decryptor can discover them or to eliminate them altogether.
Also, don't use defaults in Java cryptography: they're not portable. For example, Cipher.getInstance() takes a string of the form alg/mode/padding. Always specify all three. I notice you also use the default no-args String.getBytes() method. Always specify a Charset, and almost always "UTF8" is the best choice.

Android: Having issues saving encrypted username/password

I have the following class I use to store encrypted preferences to use with my application (using interface with 3rd part site which does not support OAuth)...
public class CryptoTranslator {
private static SecretKey SEC_KEY;
/**
* #return the sEC_KEY
*/
public static SecretKey getSEC_KEY() {
return SEC_KEY;
}
public static String getSEC_KEY_String(){
return Base64.encodeToString(SEC_KEY.getEncoded(), Base64.DEFAULT);
}
/**
* #param sEC_KEY the sEC_KEY to set
*/
public static void setSEC_KEY(SecretKey sEC_KEY) {
SEC_KEY = sEC_KEY;
}
public static void setSEC_KEY_STRING(String sEC_KEY){
byte[] key = Base64.decode(sEC_KEY, Base64.DEFAULT);
SEC_KEY = new SecretKeySpec(key, 0, key.length, "AES");
}
public static void generateKey() throws NoSuchAlgorithmException {
// Generate a 256-bit key
final int outputKeyLength = 256;
SecureRandom secureRandom = new SecureRandom();
// Do *not* seed secureRandom! Automatically seeded from system entropy.
KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
keyGenerator.init(outputKeyLength, secureRandom);
SecretKey key = keyGenerator.generateKey();
SEC_KEY = key;
}
private static byte[] getRawKey() throws Exception {
if (SEC_KEY == null){
generateKey();
}
byte[] raw = SEC_KEY.getEncoded();
return raw;
}
/**
*
*
* #param clear clear text string
* #param mode this should either be Cipher.ENCRYPT_MODE or Cipher.DECRYPT_MODE
* #return
* #throws Exception
*/
private static String translate(String clear, int mode) throws Exception {
if(mode != Cipher.ENCRYPT_MODE && mode != Cipher.DECRYPT_MODE)
throw new IllegalArgumentException("Encryption invalid. Mode should be either Cipher.ENCRYPT_MODE or Cipher.DECRYPT_MODE");
SecretKeySpec skeySpec = new SecretKeySpec(getRawKey(), "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(mode, skeySpec);
byte[] encrypted = cipher.doFinal(clear.getBytes());
return new String(encrypted);
}
public static String encrypt(String clear) throws Exception {
return translate(clear,Cipher.ENCRYPT_MODE);
}
public static String decrypt(String encrypted) throws Exception {
return translate(encrypted,Cipher.DECRYPT_MODE);
}
}
So now I have encrypted and stored the data. Now I want to pull it out...
String secString = settings.getString(SEC_KEY, null);
if (secString == null) {
try {
CryptoTranslator.generateKey();
settings.edit()
.putString(SEC_KEY,
CryptoTranslator.getSEC_KEY_String()).commit();
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} else {
CryptoTranslator.setSEC_KEY_STRING(secString);
}
try {
getUserNamePassword();
} catch (Exception ex) {
Log.i("Preferences",
"There was an issue getting username and password");
isStored = CRED_STATUS_DEF;
}
...
private static void getUserNamePassword() throws Exception {
isStored = settings.getBoolean(CRED_STATUS, CRED_STATUS_DEF);
if (isStored) {
if (settings.contains(USERNAME_KEY))
username = settings.getString(USERNAME_KEY, "");
if (settings.contains(PASSWORD_KEY))
password = settings.getString(PASSWORD_KEY, "");
}
isUsernamePasswordValid();
if (isStored) {
String username2 = CryptoTranslator.decrypt(username);
Log.d("Security", "Username encrypted");
String password2 = CryptoTranslator.decrypt(password);
username = username2;
password = password2;
Log.d("Security", "Password encrypted");
}
}
But this gives me the following error....
javax.crypto.IllegalBlockSizeException: last block incomplete in decryption
Can someone see what I am doing wrong?
Update
Ok per the response I went ahead and changed my code to the following...
public static final int IV_LENGTH = 16;
private static final String RANDOM_ALGORITHM = "SHA1PRNG";
...
private static String translate(String clear, int mode) throws Exception {
if (mode != Cipher.ENCRYPT_MODE && mode != Cipher.DECRYPT_MODE)
throw new IllegalArgumentException(
"Encryption invalid. Mode should be either Cipher.ENCRYPT_MODE or Cipher.DECRYPT_MODE");
SecretKeySpec skeySpec = new SecretKeySpec(getRawKey(), "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
IvParameterSpec ivSpec = new IvParameterSpec(generateIv());
cipher.init(mode, skeySpec, ivSpec);
byte[] encrypted = cipher.doFinal(clear.getBytes());
return new String(encrypted);
}
...
private static byte[] generateIv() throws NoSuchAlgorithmException,
NoSuchProviderException {
SecureRandom random = SecureRandom.getInstance(RANDOM_ALGORITHM);
byte[] iv = new byte[IV_LENGTH];
random.nextBytes(iv);
return iv;
}
Now I get...
javax.crypto.BadPaddingException: pad block corrupted
To try and use hex changed to...
private static byte[] translate(byte[] val, int mode) throws Exception {
if (mode != Cipher.ENCRYPT_MODE && mode != Cipher.DECRYPT_MODE)
throw new IllegalArgumentException(
"Encryption invalid. Mode should be either Cipher.ENCRYPT_MODE or Cipher.DECRYPT_MODE");
SecretKeySpec skeySpec = new SecretKeySpec(getRawKey(), "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
IvParameterSpec ivSpec = new IvParameterSpec(generateIv());
cipher.init(mode, skeySpec, ivSpec);
byte[] encrypted = cipher.doFinal(val);
return encrypted;
}
This seems to almost work (I am getting the .com back) but the chars are still pretty jumbled.
public static String encrypt(String clear) throws Exception {
byte[] test = translate(clear.getBytes(), Cipher.ENCRYPT_MODE);
return new String(Hex.encodeHex(test));
}
public static String decrypt(String encrypted) throws Exception {
return new String(translate(Hex.decodeHex(encrypted.toCharArray()), Cipher.DECRYPT_MODE));
}
*The converting to Hex and back is screwed up here.

So there are a couple of issues with your code.
First is the output of an AES cipher is not character data, you are mangling your ciphertext by trying to put it in a String. When you try to decrypt your mangled ciphertext it is now the wrong length. You need to Base64 or Hex encode the ciphertext if you want to store it in a String and then decode it back in to a byte[] before decrypting it.
Second, when you specify just AES for your cipher spec Java expands that to AES/ECB/PKCS5Padding. ECB is an insecure cipher mode if you intend to encrypt more than 1 block of data (16 bytes for AES). I recommend you switch to a different spec AES/CBC/PKCS5Padding should be acceptable. Using a mode other than ECB will require an Initialization Vector (IV). The IV should be randomly generated but does not need to be secret, so you can store as plaintext with your ciphertext as you'll need it to decrypt as well. The initialization vector needs to be one block in length (16 bytes for AES). Do not reuse the same IV with the same AES key ever, generate a new IV for each encryption being done.
Finally, if your going to store IV + ciphertext in a third party service I recommend you add a MAC (such as HMACSHA1). A MAC will ensure the integrity of your IV + ciphertext before you attempt to decrypt it. A MAC will require a secret key as well, and you should not use the same key you generated for the cipher itself. You can prepend the generated MAC to your IV + ciphertext, so now you are storing MAC + IV + ciphertext.

Android AES client side + PHP AES server side it will throw this error :)
The solution is:
cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
Please search over the internet for the full source code. I am under NDA and to lazzy to make anonymous my whole code regarding this part, but I am sure you will find it.

"Wrong algorithm" Error when trying to Decrypt in Java

I am first going to describe the problem which I have, and then give some background to what I am trying to do. Finally I shall paste some relevant code snippets.
I am trying to implement secret key encryption/decryption using the method specified in https://stackoverflow.com/a/992413/171993. If I use that example as-is, it works (although I did notice that I need to re-instantiate the Cipher class, otherwise the decryption produces garbage). However, in my implementation I get the following exception:
java.security.InvalidKeyException: Wrong algorithm: AES or Rijndael required
at com.sun.crypto.provider.AESCrypt.init(AESCrypt.java:77)
at com.sun.crypto.provider.CipherBlockChaining.init(CipherBlockChaining.java:91)
at com.sun.crypto.provider.CipherCore.init(CipherCore.java:469)
at com.sun.crypto.provider.AESCipher.engineInit(AESCipher.java:217)
at javax.crypto.Cipher.implInit(Cipher.java:790)
at javax.crypto.Cipher.chooseProvider(Cipher.java:848)
at javax.crypto.Cipher.init(Cipher.java:1347)
at javax.crypto.Cipher.init(Cipher.java:1281)
at securitytest.SecurityManager.getCipher(SecurityManager.java:175)
at securitytest.SecurityManager.decryptSecretKey(SecurityManager.java:379)
at securitytest.SecurityManager.<init>(SecurityManager.java:82)
at securitytest.Test.main(Test.java:44)
To beat off the obvious question, yes, I do use the same algorithm: in fact, I assigned AES/CBC/PKCS5Padding to a constant and use that for instantiating both the Cipher class for encryption and decryption. I have also tried using only AES instantiate Cipher for the decryption, but that did not work either.
What I am trying to do is to password-protect a secret key by using AES/CBC/PKCS5Padding. I generate a random salt and initialisation vector. After encrypting the secret key, I append the initialisation vector (an array of bytes) to the encrypted value (also an array of bytes, creating a new array). I then encode this value in Base64 and store it in a Sqlite database, along with the salt (which, for the sake of simplicity, I store as a comma-separated string of values). However when I try to decrypt, I get the above exception. I can verify that directly after my call to the encryption method and directly before the decryption method, the following values are exactly the same (when converted to Base64 so that I can print it out):
The salt
The initialisation vector
The encrypted secret key (i.e. the cipher text)
I have tried both Java 6 and 7: both give the same results. I have also ruled out the unlimited strength jurisdiction policy files as an issue. In fact, I get a similar error if I substitute "AES" with another algorithm and adjust the length of the salt accordingly (for example "Blowfish" with IV length 8, which produces java.security.InvalidKeyException: Wrong algorithm: Blowfish required).
Google has not been able to help me with this problem. If anyone can shed some light on this, I would be very appreciative.
Here are some code snippets (my apologies, it is a little rough):
private static final int INIT_VECTOR_LENGTH = 16;
private static final int PRIVATE_KEY_LENGTH = 128;
private static final int SALT_LENGTH = 16;
private static final int PBE_KEYSPEC_ITERATIONS = 65536;
private static final String CIPHER_ALGORITHM = "AES";
private static final String CIPHER_ALGORITHM_MODE = "CBC";
private static final String CIPHER_ALGORITHM_PADDING = "PKCS5Padding";
private static final String DIGEST = "SHA1";
private static final String PLAINTEXT_ENCODING = "UTF8";
private static final String PRNG = DIGEST + "PRNG";
private static final String SECRET_KEY_FACTORY = "PBKDF2WithHmac" + DIGEST;
private static final String CIPHER = CIPHER_ALGORITHM + "/" + CIPHER_ALGORITHM_MODE + "/" + CIPHER_ALGORITHM_PADDING;
private IvParameterSpec ivSpec;
private final BASE64Encoder encoder = new BASE64Encoder();
private final BASE64Decoder decoder = new BASE64Decoder();
private Cipher getCipher(SecretKey key, int mode) {
Cipher cipher = null;
try {
cipher = Cipher.getInstance(CIPHER);
}
catch (NoSuchAlgorithmException e) {System.err.println(System.err.println(e.getMessage());}
catch (NoSuchPaddingException e) {System.err.println(e.getMessage());}
try {
if (mode == Cipher.ENCRYPT_MODE) {
cipher.init(mode, key);
AlgorithmParameters params = cipher.getParameters();
ivSpec = params.getParameterSpec(IvParameterSpec.class);
}
else {
/* This is my point-of-failure. */
cipher.init(mode, key, ivSpec);
}
}
catch (InvalidKeyException e) {System.err.println(e.getMessage());}
catch (InvalidAlgorithmParameterException e) {System.err.println(e.getMessage());}
catch (InvalidParameterSpecException e) {System.err.println(e.getMessage());}
return cipher;
}
private SecurityData.Secrets generateSecrets(SecretKey decryptedKey, byte[] salt, String passphrase) {
/* Generate a new key for encrypting the secret key. */
byte[] raw = null;
PBEKey key = null;
PBEKeySpec password = new PBEKeySpec(passphrase.toCharArray(), salt, PBE_KEYSPEC_ITERATIONS, PRIVATE_KEY_LENGTH);
SecretKeyFactory factory = null;
byte[] initVector = null;
byte[] secretKeyBytes = decryptedKey.getEncoded();
try {
factory = SecretKeyFactory.getInstance(SECRET_KEY_FACTORY);
key = (PBEKey) factory.generateSecret(password);
}
catch (NoSuchAlgorithmException e) {System.err.println(e.getMessage());}
catch (InvalidKeySpecException e) {System.err.println(e.getMessage());}
SecretKeySpec newKey = new SecretKeySpec(key.getEncoded(), CIPHER_ALGORITHM);
/* Encrypt the secret key. */
IvParameterSpec ivSpec = new IvParameterSpec(initVector);
Cipher cipher = getCipher(newKey, ivSpec, Cipher.ENCRYPT_MODE);
try {
raw = cipher.doFinal(secretKeyBytes);
}
catch (IllegalBlockSizeException e) {System.err.println(e.getMessage());}
catch (BadPaddingException e) {System.err.println(e.getMessage());}
return new SecurityData.Secrets(encoder.encode(concatByteArrays(initVector, raw)), joinByteArray(salt));
}
private SecretKey decryptSecretKey(String encryptedKey, String salt, String passphrase) {
/* Get initialisation vector. */
byte[] raw = null, decoded = null, initVector = new byte[INIT_VECTOR_LENGTH];
try {
decoded = decoder.decodeBuffer(encryptedKey);
} catch (IOException e) {System.err.println(e.getMessage());}
System.arraycopy(decoded, 0, initVector, 0, INIT_VECTOR_LENGTH);
raw = new byte[decoded.length-INIT_VECTOR_LENGTH];
System.arraycopy(decoded, INIT_VECTOR_LENGTH, raw, 0, decoded.length-INIT_VECTOR_LENGTH);
IvParameterSpec ivSpec = new IvParameterSpec(initVector);
/* Generate the key. */
byte[] rawSalt = splitByteArrayString(salt);
PBEKeySpec password = new PBEKeySpec(passphrase.toCharArray(), rawSalt, PBE_KEYSPEC_ITERATIONS, PRIVATE_KEY_LENGTH);
SecretKeyFactory factory = null;
PBEKey key = null;
try {
factory = SecretKeyFactory.getInstance(SECRET_KEY_FACTORY);
key = (PBEKey) factory.generateSecret(password);
}
catch (NoSuchAlgorithmException e) {System.err.println(e.getMessage());}
catch (InvalidKeySpecException e) {System.err.println(e.getMessage());}
Cipher cipher = getCipher(key, Cipher.DECRYPT_MODE);
/* Decrypt the message. */
byte[] stringBytes = null;
try {
stringBytes = cipher.doFinal(raw);
}
catch (IllegalBlockSizeException e) {System.err.println(e.getMessage());}
catch (BadPaddingException e) {System.err.println(e.getMessage());}
/* Converts the decoded message to a String. */
String clear = null;
try {
clear = new String(stringBytes, PLAINTEXT_ENCODING);
}
catch (UnsupportedEncodingException e) {System.err.println(e.getMessage());}
return new SecretKeySpec(clear.getBytes(), CIPHER_ALGORITHM);
}

The SecretKey object needs to return "AES" from its getAlgorithm() method. That's why the example has these steps:
SecretKey tmp = factory.generateSecret(spec);
SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "AES");