@Override
public String decrypt(ZWEncryptedData encryptedData) throws ZWKeyCrypterException {
try {
String encrypted = encryptedData.getEncryptedData();
Cipher decryptionCipher = Cipher.getInstance(CIPHER_ALGORITHM);
int ivLength = decryptionCipher.getBlockSize();
String ivHex = encrypted.substring(0, ivLength * 2);
String encryptedHex = encrypted.substring(ivLength * 2);
IvParameterSpec ivspec = new IvParameterSpec(ZiftrUtils.hexStringToBytes(ivHex));
decryptionCipher.init(Cipher.DECRYPT_MODE, this.secretKey, ivspec);
byte[] decryptedText = decryptionCipher.doFinal(ZiftrUtils.hexStringToBytes(encryptedHex));
String decrypted = new String(decryptedText, "UTF-8");
return decrypted;
} catch (Exception e) {
throw new ZWKeyCrypterException("Unable to decrypt", e);
}
}
private static byte[] generateIv(int ivLength) {
SecureRandom random = ZiftrUtils.createTrulySecureRandom();
if (random == null) {
String rngError = ZWApplication.getApplication().getString(R.string.zw_dialog_error_rng);
ZiftrDialogManager.showSimpleAlert(rngError);
}
byte[] iv = new byte[ivLength];
random.nextBytes(iv);
return iv;
}
public static String generateSalt() throws ZWKeyCrypterException {
try {
SecureRandom random = ZiftrUtils.createTrulySecureRandom();
if (random == null) {
String rngError = ZWApplication.getApplication().getString(R.string.zw_dialog_error_rng);
ZiftrDialogManager.showSimpleAlert(rngError);
}
byte[] salt = new byte[SALT_LENGTH];
random.nextBytes(salt);
String saltHex = ZiftrUtils.bytesToHexString(salt);
try {
ZLog.log("salt: " + salt);
} catch (Exception e) {
System.out.println("salt: " + saltHex);
}
return saltHex;
} catch (Exception e) {
throw new ZWKeyCrypterException("Unable to generate salt", e);
}
}
@Override
public ZWEncryptedData encrypt(String clearText) throws ZWKeyCrypterException {
try {
Cipher encryptionCipher = Cipher.getInstance(CIPHER_ALGORITHM);
byte[] iv = generateIv(encryptionCipher.getBlockSize());
String ivHex = ZiftrUtils.bytesToHexString(iv);
IvParameterSpec ivSpec = new IvParameterSpec(iv);
encryptionCipher.init(Cipher.ENCRYPT_MODE, this.secretKey, ivSpec);
byte[] encryptedText = encryptionCipher.doFinal(clearText.getBytes("UTF-8"));
String encryptedHex = ZiftrUtils.bytesToHexString(encryptedText);
// Why are we appending these values?
// AES requires a random initialization vector (IV). We save the IV
// with the encrypted value so we can get it back later in decrypt()
return new ZWEncryptedData(ivHex + encryptedHex);
} catch (Exception e) {
System.out.println("error message: " + e.getMessage());
throw new ZWKeyCrypterException("Unable to encrypt", e);
}
}
public static SecretKey generateSecretKey(String password, String salt)
throws ZWKeyCrypterException {
try {
PBEKeySpec pbeKeySpec =
new PBEKeySpec(
password.toCharArray(),
ZiftrUtils.hexStringToBytes(salt),
PBE_ITERATION_COUNT,
KEY_LENGTH);
SecretKeyFactory factory = SecretKeyFactory.getInstance(PBE_ALGORITHM);
SecretKey tmp = factory.generateSecret(pbeKeySpec);
SecretKey secret = new SecretKeySpec(tmp.getEncoded(), SECRET_KEY_ALGORITHM);
return secret;
} catch (Exception e) {
throw new ZWKeyCrypterException("Unable to get secret key", e);
}
}
@Override
public byte[] decryptToBytes(ZWEncryptedData encryptedData) throws ZWKeyCrypterException {
return ZiftrUtils.hexStringToBytes(decrypt(encryptedData));
}