I have run into a problem - an existing program uses the code below to encrypt data
public static String encryptData(String data, final String key) {
try {
byte[] kb=key.getBytes("utf-8");
byte[] dig= MessageDigest.getInstance("SHA-1").digest(kb);
byte[] kdig= Arrays.copyOf(dig, 24);
final SecretKeySpec secretKeySpec = new SecretKeySpec(kdig, "DESede");
final Cipher instance = Cipher.getInstance("DESede");
instance.init(ENCRYPT_MODE, secretKeySpec);
byte[] ecb=instance.doFinal(data.getBytes("utf-8"));
byte[] enb64=Base64.encode(ecb, Base64.DEFAULT);
return new String(enb64);
} catch (Exception ex) {
ErmsLogger.e(TAG, ex.getMessage());
return null;
}
}
I need to write code on Node.Js that decrypts this encrypted data. So far - I have come up with
function decryptData(encrpted_data,fn){
var hashedKey = crypto.createHash('sha1').update(config.dataPassword).digest('hex');
if(hashedKey.length < 48){
var num=48 - hashedKey.length;
for(var i=0;i < num; i++){
hashedKey +='0';
}
}
var key=Buffer.from(hashedKey, 'hex');
var decipher = crypto.createDecipher('des-ede', key);
decoded = decipher.update(encrpted_data, 'base64', 'utf8');
decoded += decipher.final('utf8');
log.debug(JSON.stringify(decoded));
return fn(decoded);
}
I keep on running into
Error: error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt
at Decipher.final (internal/crypto/cipher.js:104:26)
whenever I try to decrypt data sent from the android app.
the working decryption code on Android (Java) is
public static String decryptData(final String data, final String password) throws Exception {
MessageDigest instance=MessageDigest.getInstance("SHA-1");
byte[] passworddigest=instance.digest(password.getBytes("utf-8"));
byte[] key=Arrays.copyOf(passworddigest, 24);
final SecretKeySpec secretKeySpec = new SecretKeySpec(key, "DESede");
final byte[] decodeddata = Base64.decode(data.getBytes("utf-8"), Base64.DEFAULT);
final Cipher ciperInstance = Cipher.getInstance("DESede");
ciperInstance.init(DECRYPT_MODE, secretKeySpec);
byte[] res= ciperInstance.doFinal(decodeddata);
return new String(res, "UTF-8");
}
Could you assist me translate this in Node?
After a bit of research and hitting my head against it - I finally came up with something that works
function decryptData(encrpted_data,fn){
var encodeKey = crypto.createHash('sha1').update(config.dataPassword).digest('hex');
var cryptkey=Buffer.alloc(24);
encodeKey.copy(cryptkey);
var decipher = crypto.createDecipheriv('des-ede3', cryptkey,'');
decipher.setAutoPadding(true);
decoded = decipher.update(encrpted_data, 'base64', 'utf8');
decoded += decipher.final('utf8');
log.debug(JSON.stringify(decoded));
return fn(decoded);
}
the explanation -
crypto.createDecipher() - internally uses the MD5 hash for the key passed to it and so it really doesn't matter what key value you send in - it will be changed. So the best option is to use createDecipheriv which accepts a raw key. This allows you to hash your key outside before passing it in. Since I was not using any IV - I passed the value of ''.
In Java (Android) DESede is really TripleDES and the equivalent on on crypto is 'des-ede3' and not 'des-ede'.
I hope this saves someone a couple of hours.
I kind of got stuck with this exception:
java.lang.RuntimeException: error:0407806d:RSA routines:decrypt:DATA_LEN_NOT_EQUAL_TO_MOD_LEN
at com.android.org.conscrypt.NativeCrypto.RSA_private_decrypt(Native Method)
at com.android.org.conscrypt.OpenSSLCipherRSA.engineDoFinal(OpenSSLCipherRSA.java:274)
at javax.crypto.Cipher.doFinal(Cipher.java:1440)
at javax.crypto.CipherInputStream.close(CipherInputStream.java:190)
...
It is thrown when I close the CipherInputStream on Android Marshmallow. Everything seems to work with earlier Android Versions.
What does DATA_LEN_NOT_EQUAL_TO_MOD_LEN mean? Why does it seem to decrypt (call to RSA_private_decrypt) when it should free resource handles (close)?
UPDATE:
I managed to reproduce the error with some test code. It encrypts and decrypts "foobar". One time using the cipher directly and one time through a CipherInputStream (like it's done in the original app).
Everything works on android < 6 and the non-streaming code is even working on android 6.
I was able to get the streaming code to work on android 6 when I changed the explicit cipher RSA/ECB/PKCS1Padding to generic RSA.
But I would bet that it's there for a reason ;)
static final String RSA_ALGO = "RSA/ECB/PKCS1Padding";
// static final String RSA_ALGO = "RSA";
private void _testCrypto2() throws Exception {
KeyPairGenerator keyGen;
KeyPair keys;
byte[] encrypted;
byte[] decrypted;
String input;
String output;
keyGen = KeyPairGenerator.getInstance("RSA");
keyGen.initialize(2048);
keys = keyGen.generateKeyPair();
input = "foobar";
// Plain crypto.
encrypted = this.RSAEncrypt(input, keys.getPublic());
output = this.RSADecrypt(encrypted, keys.getPrivate());
// Streaming crypto.
encrypted = this.RSAEncryptStream(input, keys.getPublic());
output = this.RSADecryptStream(encrypted, keys.getPrivate());
}
public byte[] RSAEncrypt(final String plain, PublicKey _publicKey) throws Exception {
byte[] encryptedBytes;
Cipher cipher;
cipher = Cipher.getInstance(RSA_ALGO);
cipher.init(Cipher.ENCRYPT_MODE, _publicKey);
encryptedBytes = cipher.doFinal(plain.getBytes());
return encryptedBytes;
}
public String RSADecrypt(final byte[] encryptedBytes, PrivateKey _privateKey) throws Exception {
Cipher cipher;
byte[] decryptedBytes;
String decrypted;
cipher = Cipher.getInstance(RSA_ALGO);
cipher.init(Cipher.DECRYPT_MODE, _privateKey);
decryptedBytes = cipher.doFinal(encryptedBytes);
decrypted = new String(decryptedBytes);
return decrypted;
}
public byte[] RSAEncryptStream(final String _plain, PublicKey _publicKey) throws Exception {
Cipher cipher;
InputStream in;
ByteArrayOutputStream out;
int numBytes;
byte buffer[] = new byte[0xffff];
in = new ByteArrayInputStream(_plain.getBytes());
out = new ByteArrayOutputStream();
cipher = Cipher.getInstance(RSA_ALGO);
cipher.init(Cipher.ENCRYPT_MODE, _publicKey);
try {
in = new CipherInputStream(in, cipher);
while ((numBytes = in.read(buffer)) != -1) {
out.write(buffer, 0, numBytes);
}
}
finally {
in.close();
}
return out.toByteArray();
}
public String RSADecryptStream(final byte[] _encryptedBytes, PrivateKey _privateKey) throws Exception {
Cipher cipher;
InputStream in;
ByteArrayOutputStream out;
int numBytes;
byte buffer[] = new byte[0xffff];
in = new ByteArrayInputStream(_encryptedBytes);
out = new ByteArrayOutputStream();
cipher = Cipher.getInstance(RSA_ALGO);
cipher.init(Cipher.DECRYPT_MODE, _privateKey);
try {
in = new CipherInputStream(in, cipher);
while ((numBytes = in.read(buffer)) != -1) {
out.write(buffer, 0, numBytes);
}
}
finally {
in.close();
}
return new String(out.toByteArray());
}
However, it looks like there are two directions for a fix:
Getting rid of the streaming for RSA
Removing explicit RSA cipher instantiation
What do you think?
It looks like there were some changes for the default security providers of android.
Cipher c;
Provider p;
StringBuilder bldr;
c = Cipher.getInstance("RSA");
p = cipher.getProvider();
bldr = new StringBuilder();
bldr.append(_p.getName())
.append(" ").append(_p.getVersion())
.append(" (").append(_p.getInfo()).append(")");
Log.i("test", bldr.toString());
It seems to use a version of BouncyCastle on all tested Android versions (I tested down to 2.3):
Android 5:
BC 1.5 (BouncyCastle Security Provider v1.50)
Android 6:
BC 1.52 (BouncyCastle Security Provider v1.52)
However, something changed with the "explicit" cipher:
c = Cipher.getInstance("RSA/ECB/PKCS1Padding");
Android 4.1.2:
BC 1.46 (BouncyCastle Security Provider v1.46)
Android 4.4.2:
AndroidOpenSSL 1.0 (Android's OpenSSL-backed security provider)
Android 5.1.1:
AndroidOpenSSL 1.0 (Android's OpenSSL-backed security provider)
Android 6.0.1:
AndroidKeyStoreBCWorkaround 1.0 (Android KeyStore security provider to work around Bouncy Castle)
So the final solution is setting the provider explicitly to BouncyCastle which is working on all tested android versions, even with streaming:
Provider p;
Cipher c;
p = Security.getProvider("BC");
c = Cipher.getInstance("RSA/ECB/PKCS1Padding", p);
Why I ask this question:
I know there have been a lot of questions about AES encryption, even for Android. And there are lots of code snippets if you search the Web. But on every single page, in every Stack Overflow question, I find another implementation with major differences.
So I created this question to find a "best practice". I hope we can collect a list of the most important requirements and set up an implementation that is really secure!
I read about initialization vectors and salts. Not all implementations I found had these features. So do you need it? Does it increase the security a lot? How do you implement it? Should the algorithm raise exceptions if the encrypted data cannot be decrypted? Or is that insecure and it should just return an unreadable string? Can the algorithm use Bcrypt instead of SHA?
What about these two implementations I found? Are they okay? Perfect or some important things missing? What of these is secure?
The algorithm should take a string and a "password" for encryption and then encrypt the string with that password. The output should be a string (hex or base64?) again. Decryption should be possible as well, of course.
What is the perfect AES implementation for Android?
Implementation #1:
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
public class AdvancedCrypto implements ICrypto {
public static final String PROVIDER = "BC";
public static final int SALT_LENGTH = 20;
public static final int IV_LENGTH = 16;
public static final int PBE_ITERATION_COUNT = 100;
private static final String RANDOM_ALGORITHM = "SHA1PRNG";
private static final String HASH_ALGORITHM = "SHA-512";
private static final String PBE_ALGORITHM = "PBEWithSHA256And256BitAES-CBC-BC";
private static final String CIPHER_ALGORITHM = "AES/CBC/PKCS5Padding";
private static final String SECRET_KEY_ALGORITHM = "AES";
public String encrypt(SecretKey secret, String cleartext) throws CryptoException {
try {
byte[] iv = generateIv();
String ivHex = HexEncoder.toHex(iv);
IvParameterSpec ivspec = new IvParameterSpec(iv);
Cipher encryptionCipher = Cipher.getInstance(CIPHER_ALGORITHM, PROVIDER);
encryptionCipher.init(Cipher.ENCRYPT_MODE, secret, ivspec);
byte[] encryptedText = encryptionCipher.doFinal(cleartext.getBytes("UTF-8"));
String encryptedHex = HexEncoder.toHex(encryptedText);
return ivHex + encryptedHex;
} catch (Exception e) {
throw new CryptoException("Unable to encrypt", e);
}
}
public String decrypt(SecretKey secret, String encrypted) throws CryptoException {
try {
Cipher decryptionCipher = Cipher.getInstance(CIPHER_ALGORITHM, PROVIDER);
String ivHex = encrypted.substring(0, IV_LENGTH * 2);
String encryptedHex = encrypted.substring(IV_LENGTH * 2);
IvParameterSpec ivspec = new IvParameterSpec(HexEncoder.toByte(ivHex));
decryptionCipher.init(Cipher.DECRYPT_MODE, secret, ivspec);
byte[] decryptedText = decryptionCipher.doFinal(HexEncoder.toByte(encryptedHex));
String decrypted = new String(decryptedText, "UTF-8");
return decrypted;
} catch (Exception e) {
throw new CryptoException("Unable to decrypt", e);
}
}
public SecretKey getSecretKey(String password, String salt) throws CryptoException {
try {
PBEKeySpec pbeKeySpec = new PBEKeySpec(password.toCharArray(), HexEncoder.toByte(salt), PBE_ITERATION_COUNT, 256);
SecretKeyFactory factory = SecretKeyFactory.getInstance(PBE_ALGORITHM, PROVIDER);
SecretKey tmp = factory.generateSecret(pbeKeySpec);
SecretKey secret = new SecretKeySpec(tmp.getEncoded(), SECRET_KEY_ALGORITHM);
return secret;
} catch (Exception e) {
throw new CryptoException("Unable to get secret key", e);
}
}
public String getHash(String password, String salt) throws CryptoException {
try {
String input = password + salt;
MessageDigest md = MessageDigest.getInstance(HASH_ALGORITHM, PROVIDER);
byte[] out = md.digest(input.getBytes("UTF-8"));
return HexEncoder.toHex(out);
} catch (Exception e) {
throw new CryptoException("Unable to get hash", e);
}
}
public String generateSalt() throws CryptoException {
try {
SecureRandom random = SecureRandom.getInstance(RANDOM_ALGORITHM);
byte[] salt = new byte[SALT_LENGTH];
random.nextBytes(salt);
String saltHex = HexEncoder.toHex(salt);
return saltHex;
} catch (Exception e) {
throw new CryptoException("Unable to generate salt", e);
}
}
private byte[] generateIv() throws NoSuchAlgorithmException, NoSuchProviderException {
SecureRandom random = SecureRandom.getInstance(RANDOM_ALGORITHM);
byte[] iv = new byte[IV_LENGTH];
random.nextBytes(iv);
return iv;
}
}
Source: http://pocket-for-android.1047292.n5.nabble.com/Encryption-method-and-reading-the-Dropbox-backup-td4344194.html
Implementation #2:
import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
/**
* Usage:
* <pre>
* String crypto = SimpleCrypto.encrypt(masterpassword, cleartext)
* ...
* String cleartext = SimpleCrypto.decrypt(masterpassword, crypto)
* </pre>
* #author ferenc.hechler
*/
public class SimpleCrypto {
public static String encrypt(String seed, String cleartext) throws Exception {
byte[] rawKey = getRawKey(seed.getBytes());
byte[] result = encrypt(rawKey, cleartext.getBytes());
return toHex(result);
}
public static String decrypt(String seed, String encrypted) throws Exception {
byte[] rawKey = getRawKey(seed.getBytes());
byte[] enc = toByte(encrypted);
byte[] result = decrypt(rawKey, enc);
return new String(result);
}
private static byte[] getRawKey(byte[] seed) throws Exception {
KeyGenerator kgen = KeyGenerator.getInstance("AES");
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
sr.setSeed(seed);
kgen.init(128, sr); // 192 and 256 bits may not be available
SecretKey skey = kgen.generateKey();
byte[] raw = skey.getEncoded();
return raw;
}
private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
byte[] encrypted = cipher.doFinal(clear);
return encrypted;
}
private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.DECRYPT_MODE, skeySpec);
byte[] decrypted = cipher.doFinal(encrypted);
return decrypted;
}
public static String toHex(String txt) {
return toHex(txt.getBytes());
}
public static String fromHex(String hex) {
return new String(toByte(hex));
}
public static byte[] toByte(String hexString) {
int len = hexString.length()/2;
byte[] result = new byte[len];
for (int i = 0; i < len; i++)
result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
return result;
}
public static String toHex(byte[] buf) {
if (buf == null)
return "";
StringBuffer result = new StringBuffer(2*buf.length);
for (int i = 0; i < buf.length; i++) {
appendHex(result, buf[i]);
}
return result.toString();
}
private final static String HEX = "0123456789ABCDEF";
private static void appendHex(StringBuffer sb, byte b) {
sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
}
}
Source: http://www.tutorials-android.com/learn/How_to_encrypt_and_decrypt_strings.rhtml
Neither implementation you give in your question is entirely correct, and neither implementation you give should be used as is. In what follows, I will discuss aspects of password-based encryption in Android.
Keys and Hashes
I will start discussing the password-based system with salts. The salt is a randomly generated number. It is not "deduced". Implementation 1 includes a generateSalt() method that generates a cryptographically strong random number. Because the salt is important to security, it should be kept secret once it is generated, though it only needs to be generated once. If this is a Web site, it's relatively easy to keep the salt secret, but for installed applications (for desktop and mobile devices), this will be much more difficult.
The method getHash() returns a hash of the given password and salt, concatenated into a single string. The algorithm used is SHA-512, which returns a 512-bit hash. This method returns a hash that's useful for checking a string's integrity, so it might as well be used by calling getHash() with just a password or just a salt, since it simply concatenates both parameters. Since this method won't be used in the password-based encryption system, I won't be discussing it further.
The method getSecretKey(), derives a key from a char array of the password and a hex-encoded salt, as returned from generateSalt(). The algorithm used is PBKDF1 (I think) from PKCS5 with SHA-256 as the hash function, and returns a 256-bit key. getSecretKey() generates a key by repeatedly generating hashes of the password, salt, and a counter (up to the iteration count given in PBE_ITERATION_COUNT, here 100) in order to increase the time needed to mount a brute-force attack. The salt's length should be at least as long as the key being generated, in this case, at least 256 bits. The iteration count should be set as long as possible without causing unreasonable delay. For more information on salts and iteration counts in key derivation, see section 4 in RFC2898.
The implementation in Java's PBE, however, is flawed if the password contains Unicode characters, that is, those that require more than 8 bits to be represented. As stated in PBEKeySpec, "the PBE mechanism defined in PKCS #5 looks at only the low order 8 bits of each character". To work around this problem, you can try generating a hex string (which will contain only 8-bit characters) of all 16-bit characters in the password before passing it to PBEKeySpec. For example, "ABC" becomes "004100420043". Note also that PBEKeySpec "requests the password as a char array, so it can be overwritten [with clearPassword()] when done". (With respect to "protecting strings in memory", see this question.) I don't see any problems, though, with representing a salt as a hex-encoded string.
Encryption
Once a key is generated, we can use it to encrypt and decrypt text.
In implementation 1, the cipher algorithm used is AES/CBC/PKCS5Padding, that is, AES in the Cipher Block Chaining (CBC) cipher mode, with padding defined in PKCS#5. (Other AES cipher modes include counter mode (CTR), electronic codebook mode (ECB), and Galois counter mode (GCM). Another question on Stack Overflow contains answers that discuss in detail the various AES cipher modes and the recommended ones to use. Be aware, too, that there are several attacks on CBC mode encryption, some of which are mentioned in RFC 7457.)
Note that you should use an encryption mode that also checks the encrypted data for integrity (e.g., authenticated encryption with associated data, AEAD, described in RFC 5116). However, AES/CBC/PKCS5Padding doesn't provide integrity checking, so it alone is not recommended. For AEAD purposes, using a secret that's at least twice as long as a normal encryption key is recommended, to avoid related key attacks: the first half serves as the encryption key, and the second half serves as the key for the integrity check. (That is, in this case, generate a single secret from a password and salt, and split that secret in two.)
Java Implementation
The various functions in implementation 1 use a specific provider, namely "BC", for its algorithms. In general, though, it is not recommended to request specific providers, since not all providers are available on all Java implementations, whether for lack of support, to avoid code duplication, or for other reasons. This advice has especially become important since the release of Android P preview in early 2018, because some functionality from the "BC" provider has been deprecated there — see the article "Cryptography Changes in Android P" in the Android Developers Blog. See also the Introduction to Oracle Providers.
Thus, PROVIDER should not exist and the string -BC should be removed from PBE_ALGORITHM. Implementation 2 is correct in this respect.
It is inappropriate for a method to catch all exceptions, but rather to handle only the exceptions it can. The implementations given in your question can throw a variety of checked exceptions. A method can choose to wrap only those checked exceptions with CryptoException, or specify those checked exceptions in the throws clause. For convenience, wrapping the original exception with CryptoException may be appropriate here, since there are potentially many checked exceptions the classes can throw.
SecureRandom in Android
As detailed in the article "Some SecureRandom Thoughts", in the Android Developers Blog, the implementation of java.security.SecureRandom in Android releases before 2013 has a flaw that reduces the strength of random numbers it delivers. This flaw can be mitigated as described in that article.
#2 should never be used as it uses only "AES" (which means ECB mode encryption on text, a big no-no) for the cipher. I'll just talk about #1.
The first implementation seems to adhere to best practices for encryption. The constants are generally OK, although both the salt size and the number of iterations for performing PBE are on the short side. Futhermore, it seems to be for AES-256 since the PBE key generation uses 256 as a hard coded value (a shame after all those constants). It uses CBC and PKCS5Padding which is at least what you would expect.
Completely missing is any authentication/integrity protection, so an attacker can change the cipher text. This means that padding oracle attacks are possible in a client/server model. It also means that an attacker can try and change the encrypted data. This will likely result in some error somewhere becaues the padding or content is not accepted by the application, but that's not a situation that you want to be in.
Exception handling and input validation could be enhanced, catching Exception is always wrong in my book. Furhtermore, the class implements ICrypt, which I don't know. I do know that having only methods without side effects in a class is a bit weird. Normally, you would make those static. There is no buffering of Cipher instances etc., so every required object gets created ad-nauseum. However, you can safely remove ICrypto from the definition it seems, in that case you could also refactor the code to static methods (or rewrite it to be more object oriented, your choice).
The problem is that any wrapper always makes assumptions about the use case. To say that a wrapper is right or wrong is therefore bunk. This is why I always try to avoid generating wrapper classes. But at least it does not seem explicitly wrong.
You have asked a pretty interesting question. As with all algorithms the cipher key is the "secret sauce", since once that's known to the public, everything else is too. So you look into ways to this document by Google
security
Besides Google In-App Billing also gives thoughts on security which is insightful as well
billing_best_practices
Use BouncyCastle Lightweight API. It provides 256 AES With PBE and Salt.
Here sample code, which can encrypt/decrypt files.
public void encrypt(InputStream fin, OutputStream fout, String password) {
try {
PKCS12ParametersGenerator pGen = new PKCS12ParametersGenerator(new SHA256Digest());
char[] passwordChars = password.toCharArray();
final byte[] pkcs12PasswordBytes = PBEParametersGenerator.PKCS12PasswordToBytes(passwordChars);
pGen.init(pkcs12PasswordBytes, salt.getBytes(), iterationCount);
CBCBlockCipher aesCBC = new CBCBlockCipher(new AESEngine());
ParametersWithIV aesCBCParams = (ParametersWithIV) pGen.generateDerivedParameters(256, 128);
aesCBC.init(true, aesCBCParams);
PaddedBufferedBlockCipher aesCipher = new PaddedBufferedBlockCipher(aesCBC, new PKCS7Padding());
aesCipher.init(true, aesCBCParams);
// Read in the decrypted bytes and write the cleartext to out
int numRead = 0;
while ((numRead = fin.read(buf)) >= 0) {
if (numRead == 1024) {
byte[] plainTemp = new byte[aesCipher.getUpdateOutputSize(numRead)];
int offset = aesCipher.processBytes(buf, 0, numRead, plainTemp, 0);
final byte[] plain = new byte[offset];
System.arraycopy(plainTemp, 0, plain, 0, plain.length);
fout.write(plain, 0, plain.length);
} else {
byte[] plainTemp = new byte[aesCipher.getOutputSize(numRead)];
int offset = aesCipher.processBytes(buf, 0, numRead, plainTemp, 0);
int last = aesCipher.doFinal(plainTemp, offset);
final byte[] plain = new byte[offset + last];
System.arraycopy(plainTemp, 0, plain, 0, plain.length);
fout.write(plain, 0, plain.length);
}
}
fout.close();
fin.close();
} catch (Exception e) {
e.printStackTrace();
}
}
public void decrypt(InputStream fin, OutputStream fout, String password) {
try {
PKCS12ParametersGenerator pGen = new PKCS12ParametersGenerator(new SHA256Digest());
char[] passwordChars = password.toCharArray();
final byte[] pkcs12PasswordBytes = PBEParametersGenerator.PKCS12PasswordToBytes(passwordChars);
pGen.init(pkcs12PasswordBytes, salt.getBytes(), iterationCount);
CBCBlockCipher aesCBC = new CBCBlockCipher(new AESEngine());
ParametersWithIV aesCBCParams = (ParametersWithIV) pGen.generateDerivedParameters(256, 128);
aesCBC.init(false, aesCBCParams);
PaddedBufferedBlockCipher aesCipher = new PaddedBufferedBlockCipher(aesCBC, new PKCS7Padding());
aesCipher.init(false, aesCBCParams);
// Read in the decrypted bytes and write the cleartext to out
int numRead = 0;
while ((numRead = fin.read(buf)) >= 0) {
if (numRead == 1024) {
byte[] plainTemp = new byte[aesCipher.getUpdateOutputSize(numRead)];
int offset = aesCipher.processBytes(buf, 0, numRead, plainTemp, 0);
// int last = aesCipher.doFinal(plainTemp, offset);
final byte[] plain = new byte[offset];
System.arraycopy(plainTemp, 0, plain, 0, plain.length);
fout.write(plain, 0, plain.length);
} else {
byte[] plainTemp = new byte[aesCipher.getOutputSize(numRead)];
int offset = aesCipher.processBytes(buf, 0, numRead, plainTemp, 0);
int last = aesCipher.doFinal(plainTemp, offset);
final byte[] plain = new byte[offset + last];
System.arraycopy(plainTemp, 0, plain, 0, plain.length);
fout.write(plain, 0, plain.length);
}
}
fout.close();
fin.close();
} catch (Exception e) {
e.printStackTrace();
}
}
I found a nice implementation here :
http://nelenkov.blogspot.fr/2012/04/using-password-based-encryption-on.html
and
https://github.com/nelenkov/android-pbe
That was also helpful in my quest for a good enough AES Implementation for Android