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AES encrypt file in C# and Java

I have encrypted file in C# with this method:
public byte[] Crypt(byte[] filearray, string sKey)
{
AesManaged DES = new AesManaged();
DES.Key = Encoding.UTF8.GetBytes(sKey);
DES.Mode = CipherMode.ECB;
DES.Padding = PaddingMode.PKCS7;
ICryptoTransform crypt = DES.CreateEncryptor();
byte[] cipher = crypt.TransformFinalBlock(niz, 0, filearray.Length);
String encryptedText = Convert.ToBase64String(cipher);
return cipher.ToArray();
}
Now I try to decrypt file with Java:
private static byte[] transform(string base64Key, final byte[] fileBytes) throws InvalidKeyException, InvalidAlgorithmParameterException, NoSuchProviderException
{
final byte[] keyBytes = base64Key.getBytes(StandardCharsets.UTF_8);
final byte[] ivBytes = base64Iv.getBytes(StandardCharsets.UTF_8);
final SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");
final IvParameterSpec ivSpec = new IvParameterSpec(ivBytes);
byte[] transformedBytes = null;
try
{
Security.addProvider(new BouncyCastleProvider());
final Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding");;
cipher.init(Cipher.DECRYPT_MODE, keySpec);
transformedBytes = cipher.doFinal(fileBytes);
}
catch (NoSuchAlgorithmException | NoSuchPaddingException | IllegalBlockSizeException |
BadPaddingException e)
{
e.printStackTrace();
}
return transformedBytes;
}
When I try to execute this function I get exception
javax.crypto.BadPaddingException: pad block corrupted
at org.bouncycastle.jcajce.provider.symmetric.util.BaseBlockCipher$BufferedGenericBlockCipher.doFinal(Unknown Source)
at org.bouncycastle.jcajce.provider.symmetric.util.BaseBlockCipher.engineDoFinal(Unknown Source)
at javax.crypto.Cipher.doFinal(Cipher.java:2165)

Try using a different padding, for example:
Cipher.getInstance("AES/ECB/NoPadding");
or
Cipher.getInstance("AES/ECB/PKCS5Padding");
instead of
Cipher.getInstance("AES/ECB/PKCS7Padding");

How to decrypt aes-256-cbc in Java

I have encrypted the string in php. Decrypted successfully from php and node.js. In addition, it must be decrypted by java.
Help me an example of decrypting from java?
PHP Encrypt code
/* encrypt */
$encryption_method = 'aes-256-cbc';
$secretHash = "d95acd54c6a821ff32c52825b931c194";
$iv_size = openssl_cipher_iv_length($encryption_method);
$iv = openssl_random_pseudo_bytes($iv_size);
//encrypt
$encryptedMessage = openssl_encrypt($new_token, $encryption_method, $secretHash, 0, $iv);
//Concatenate iv with data
$ciphertext = bin2hex($iv).$encryptedMessage;
/* decrypt the cipher */
$iv_size = openssl_cipher_iv_length($encryptionMethod);
$iv = hex2bin(substr($encryptedMessageWithIv, 0, $iv_size * 2));
$decryptedMessage = openssl_decrypt(substr($encryptedMessageWithIv, $iv_size * 2), $encryptionMethod, $secretHash, 0, $iv);

Below is the encryption and decryption process for a string using AES algorithm.
private static final String key = "aesEncryptionKey";
private static final String initVector = "encryptionIntVec";
public static String encrypt(String value) {
try {
IvParameterSpec iv = new IvParameterSpec(initVector.getBytes("UTF-8"));
SecretKeySpec skeySpec = new SecretKeySpec(key.getBytes("UTF-8"), "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv);
byte[] encrypted = cipher.doFinal(value.getBytes());
return Base64.encodeBase64String(encrypted);
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
public static String decrypt(String encrypted) {
try {
IvParameterSpec iv = new IvParameterSpec(initVector.getBytes("UTF-8"));
SecretKeySpec skeySpec = new SecretKeySpec(key.getBytes("UTF-8"), "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
cipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);
byte[] original = cipher.doFinal(Base64.decodeBase64(encrypted));
return new String(original);
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
In case init vector is not known, try using below code segment.
public byte[] decrypt(String encryptedString) throws DataLengthException, InvalidCipherTextException {
byte[] input = encryptedString.getBytes("UTF-8");
CBCBlockCipher cbcBlockCipher = new CBCBlockCipher(new AESEngine());
SecureRandom random = new SecureRandom();;
KeyParameter key = new KeyParameter("$secretHash".getBytes());// your key string
BlockCipherPadding blockCipherPadding = new PKCS7Padding();;
PaddedBufferedBlockCipher pbbc = new PaddedBufferedBlockCipher(cbcBlockCipher, blockCipherPadding);
int blockSize = cbcBlockCipher.getBlockSize(); // Make sure this block size is same as that used while encrypting the string.
int inputOffset = 0;
int inputLength = input.length;
int outputOffset = 0;
byte[] initializationVector = new byte[blockSize];
System.arraycopy(input, 0, initializationVector, 0, blockSize);
inputOffset += blockSize;
inputLength -= blockSize;
pbbc.init(encrypt, new ParametersWithIV(key, initializationVector));
byte[] output = new byte[pbbc.getOutputSize(inputLength) + outputOffset];
int outputLength = outputOffset + pbbc.processBytes(input, inputOffset, inputLength, output, outputOffset);
outputLength += pbbc.doFinal(output, outputLength);
return Arrays.copyOf(output, outputLength);
}

Just in case it helps someone in the future: encryption with AES/CBC/PKCS5PADDING along with the generation of a dynamic IV that is appended to the final ciphertext in Java can be done through the following code:
Encryption (JAVA)
public String encryptPlainText(String plainText) {
String cipherText = "";
try {
String keyString = "examplesecretkeyexamplesecretkey";
//Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy
Security.setProperty("crypto.policy", "unlimited");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
SecretKeySpec keyspec = new SecretKeySpec(keyString.getBytes(), "AES");
byte[] v = new byte[16];
new SecureRandom().nextBytes(v);
IvParameterSpec iv = new IvParameterSpec(v);
cipher.init(Cipher.ENCRYPT_MODE, keyspec, iv);
byte[] cipherTextByteArray = cipher.doFinal(plainText.getBytes());
//appending iv to ciphertext without any additional libraries to handle the concatenation of the two byte arrays
byte[] ivWithCipherTextByteArray = new byte[v.length + cipherTextByteArray.length];
System.arraycopy(v, 0, ivWithCipherTextByteArray, 0, v.length);
System.arraycopy(cipherTextByteArray, 0, ivWithCipherTextByteArray, v.length, cipherTextByteArray.length);
cipherText = new String(Base64.getEncoder().encode(ivWithCipherTextByteArray));
} catch (Exception e) {
LOG.info("Exception", e);
}
return cipherText;
}
Decryption of the cipherText obtained with the code above can be implemented in the following way:
Decryption (JAVA)
public static String decryptCipherText(String cipherText) {
String plainText="";
try {
String keyString = "examplesecretkeyexamplesecretkey";
Security.setProperty("crypto.policy", "unlimited");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
SecretKeySpec keyspec = new SecretKeySpec(keyString.getBytes(), "AES");
byte[] cipherTextByteArray = Base64.getDecoder().decode(cipherText);
//initialize the IvParameterSpec with the first 16 bytes of the cipherText
IvParameterSpec iv = new IvParameterSpec(Arrays.copyOfRange(cipherTextByteArray, 0, 16));
//cipherText to decrypt is now the original one with the first 16 bytes removed (the IV used above)
cipherTextByteArray = Arrays.copyOfRange(cipherTextByteArray, 16, cipherTextByteArray.length);
cipher.init(Cipher.DECRYPT_MODE, keyspec, iv);
plainText = new String(cipher.doFinal(cipherTextByteArray));
} catch (Exception e) {
LOG.info("Exception", e);
}
return plainText;
}

AES Encryption in android and decryption in php and vice versa

I am trying to learn AES by testing my code against https://aesencryption.net. I previously had an error in Base64.encodeBase64String and also Base64.decodeBase64 // encode/decode Base64. So I manipulated Base64 somehow to resolve the error. Now in my app the text is encrypted and decrypted properly, I think. But when I try to encrypt or decrypt the same text server-side (at aesencryption.net), the site is not able to decrypt my encrypted string. Please help.
Following is my code :
public class MainActivity extends AppCompatActivity {
static final String TAG = "SymmetricAlgorithmAES";
private static SecretKeySpec secretKey ;
private static byte[] key ;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Original text
// {"type":"Success","httpCode":"200","code":"200","message":{"pin":"11111"},"extra":""}
String theTestText = "hi";
TextView tvorig = (TextView)findViewById(R.id.tvorig);
tvorig.setText("\n[ORIGINAL]:\n" + theTestText + "\n");
final String strPssword = "android";
setKey(strPssword);
// Encode the original data with AES
byte[] encodedBytes = null;
try {
Cipher c = Cipher.getInstance("AES");
c.init(Cipher.ENCRYPT_MODE,secretKey);
encodedBytes = c.doFinal(theTestText.getBytes());
} catch (Exception e) {
Log.e(TAG, "AES encryption error");
}
TextView tvencoded = (TextView)findViewById(R.id.tvencoded);
tvencoded.setText("[ENCODED]:\n" +
Base64.encodeToString(encodedBytes, Base64.DEFAULT) + "\n");
Log.d(TAG, Base64.encodeToString(encodedBytes, Base64.DEFAULT));
// Decode the encoded data with AES
byte[] decodedBytes = null;
try {
Cipher c = Cipher.getInstance("AES");
c.init(Cipher.DECRYPT_MODE, secretKey);
decodedBytes = c.doFinal(encodedBytes);
} catch (Exception e) {
Log.e(TAG, "AES decryption error");
}
TextView tvdecoded = (TextView)findViewById(R.id.tvdecoded);
tvdecoded.setText("[DECODED]:\n" + new String(decodedBytes) + "\n");
}
public static void setKey(String myKey){
MessageDigest sha = null;
try {
key = myKey.getBytes("UTF-8");
System.out.println(key.length);
sha = MessageDigest.getInstance("SHA-1");
key = sha.digest(key);
key = Arrays.copyOf(key, 16); // use only first 128 bit
System.out.println(key.length);
System.out.println(new String(key,"UTF-8"));
secretKey = new SecretKeySpec(key, "AES");
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
}
Thanks in advance.

I do something like this which actually works ;)
public class AESCrypter {
private final Cipher cipher;
private final SecretKeySpec key;
private AlgorithmParameterSpec spec;
public AESCrypter(String password) throws Exception
{
// hash password with SHA-256 and crop the output to 128-bit for key
MessageDigest digest = MessageDigest.getInstance("SHA-256");
digest.update(password.getBytes("UTF-8"));
byte[] keyBytes = new byte[32];
System.arraycopy(digest.digest(), 0, keyBytes, 0, keyBytes.length);
cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
key = new SecretKeySpec(keyBytes, "AES");
spec = getIV();
}
public AlgorithmParameterSpec getIV()
{
byte[] iv = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, };
IvParameterSpec ivParameterSpec;
ivParameterSpec = new IvParameterSpec(iv);
return ivParameterSpec;
}
public String encrypt(String plainText) throws Exception
{
cipher.init(Cipher.ENCRYPT_MODE, key, spec);
byte[] encrypted = cipher.doFinal(plainText.getBytes("UTF-8"));
String encryptedText = new String(Base64.encode(encrypted, Base64.DEFAULT), "UTF-8");
return encryptedText;
}
public String decrypt(String cryptedText) throws Exception
{
cipher.init(Cipher.DECRYPT_MODE, key, spec);
byte[] bytes = Base64.decode(cryptedText, Base64.DEFAULT);
byte[] decrypted = cipher.doFinal(bytes);
String decryptedText = new String(decrypted, "UTF-8");
return decryptedText;
}
}
Call this class like this :
try {
AESCrypter _crypt = new AESCrypter("password");
String output = "";
String plainText = "top secret message";
output = _crypt.encrypt(plainText); //encrypt
System.out.println("encrypted text=" + output);
output = _crypt.decrypt(output); //decrypt
System.out.println("decrypted text=" + output);
} catch (Exception e) {
e.printStackTrace();
}
And for iPhone (Code is here) : https://github.com/Gurpartap/AESCrypt-ObjC
Hope this code works for you too :)

The PHP code uses CBC mode by default while your Java code does not specify the same, and leaves it to the underlying implementation. If I recall correctly its probably ECB/PKCS5Padding. Your PHP implementation is using 'CBC' with no padding (mcrypt doesn't support padding by default but you can do so manually).
Its very important be be very specific about mode, padding, and charset when working with different platforms else you will run into different defaults.
Try initializing your cipher as follows: Cipher.getInstance("AES/CBC/NoPadding");

fun encrypt(encrypted: String): String? {
try {
val secretKey = "secretKey" //The secret key, 32 bytes string.
val ivKey = "ivKey" // The initialization vector, 16 bytes string.
val iv = IvParameterSpec(hashIV.toByteArray(Charsets.UTF_8))
val skySpec = SecretKeySpec(hashKey.toByteArray(Charsets.UTF_8), "AES-256-CBC")
val cipher: Cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING")
cipher.init(Cipher.ENCRYPT_MODE, skySpec, iv)
val original: ByteArray = cipher.doFinal(encrypted.toByteArray())
return Base64.encode(
Base64.encodeToString(original, Base64.NO_WRAP).toByteArray(charset("UTF-8")),
Base64.NO_WRAP
).decodeToString()
} catch (ex: Exception) {
ex.printStackTrace()
}
return null
}
fun decrypt(encrypted: String?): String? {
try {
val secretKey = "secretKey" //The secret key, 32 bytes string.
val ivKey = "ivKey" // The initialization vector, 16 bytes string.
val iv = IvParameterSpec(hashIV.toByteArray(Charsets.UTF_8))
val skySpec = SecretKeySpec(hashKey.toByteArray(Charsets.UTF_8), algorithm)
val cipher: Cipher = Cipher.getInstance(transformation)
cipher.init(Cipher.DECRYPT_MODE, skySpec, iv)
val original: ByteArray = cipher.doFinal(
Base64.decode(
Base64.decode(encrypted, Base64.NO_WRAP),
Base64.NO_WRAP
)
)
return original.decodeToString()
} catch (ex: Exception) {
ex.printStackTrace()
}
return null
}
openssl_encrypt

How to decrypt a String using PBE algorithm

I have a PBE-generated secret key and I ciphered a string using the algorithm "PBEWithHmacSHA256AndAES_128" however I'm unable to decipher the said string.
Secret key generate:
private final static byte[] SALT = { (byte) 0xc9, (byte) 0x36, (byte) 0x78, (byte) 0x99, (byte) 0x52, (byte) 0x3e, (byte) 0xea,
(byte) 0xf2 };
PBEKeySpec keySpec = new PBEKeySpec(pwd.toCharArray(), SALT, 20 , 128);
try {
SecretKeyFactory kf = SecretKeyFactory.getInstance("PBEWithHmacSHA256AndAES_128");
PRIVATE_KEY = kf.generateSecret(keySpec);
} catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
e.printStackTrace();
}
Encypt String:
private static String cipherString(String string) {
PBEParameterSpec pbeParameterSpec = new PBEParameterSpec(SALT, 100);
Cipher cipher;
try {
cipher = Cipher.getInstance("PBEWithHmacSHA256AndAES_128");
cipher.init(Cipher.ENCRYPT_MODE, PRIVATE_KEY, pbeParameterSpec);
byte[] input = string.getBytes();
byte[] encryptedp = cipher.doFinal(input);
return encryptedp.toString();
} catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | InvalidAlgorithmParameterException | IllegalBlockSizeException | BadPaddingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Decrypt String:
private static String decipherString(String string) {
Cipher c;
try {
c = Cipher.getInstance("PBEWithHmacSHA256AndAES_128");
c.init(Cipher.DECRYPT_MODE, PRIVATE_KEY);
byte[] input = string.getBytes();
byte[] encryptedp = c.doFinal(input);
return encryptedp.toString();
} catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IllegalBlockSizeException | BadPaddingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}

Just use the following code that works on J2SE. As the algorithm PBEWithHmacSHA256AndAES_128 uses AES in CBC mode internally we also have to provide an IV, which is my example generated randomly. You have to use the same IV for encryption as well as decryption. For security reasons for each encryption you should use a new random IV and save it together with the encrypted text.
SecureRandom rnd = new SecureRandom();
byte[] iv = new byte[16];
rnd.nextBytes(iv);
String password = "password";
byte[] plaintext = "plaintext".getBytes(StandardCharsets.UTF_8);
IvParameterSpec ivParamSpec = new IvParameterSpec(iv);
PBEParameterSpec pbeParamSpec = new PBEParameterSpec(SALT, 10000, ivParamSpec);
PBEKeySpec keySpec = new PBEKeySpec(password.toCharArray());
try {
SecretKeyFactory kf = SecretKeyFactory.getInstance("PBEWithHmacSHA256AndAES_128");
SecretKey secretKey = kf.generateSecret(keySpec);
// On J2SE the SecretKeyfactory does not actually generate a key, it just wraps the password.
// The real encryption key is generated later on-the-fly when initializing the cipher
System.out.println(new String(secretKey.getEncoded()));
// Encrypt
Cipher enc = Cipher.getInstance("PBEWithHmacSHA256AndAES_128");
enc.init(Cipher.ENCRYPT_MODE, secretKey, pbeParamSpec);
byte[] encrypted = enc.doFinal(plaintext);
String encryptedBase64 = new BASE64Encoder().encode(encrypted);
System.out.println("Encrypted text: " + encryptedBase64);
// Decrypt
Cipher dec = Cipher.getInstance("PBEWithHmacSHA256AndAES_128");
dec.init(Cipher.DECRYPT_MODE, secretKey, pbeParamSpec);
byte[] decrypted = dec.doFinal(new BASE64Decoder().decode(encryptedBase64));
String message = new String(decrypted, StandardCharsets.UTF_8);
System.out.println(message);
} catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
e.printStackTrace();
}

Not Generating Proper AES Key Size with ECDH KeyAgreement in Java

I'd like to be able to generate proper AES keys from an ECDH key agreement. However, when I generate the secret key, I get a key with an invalid length, usually 66 bits. Here's the error:
java.security.InvalidKeyException: Key length not 128/192/256 bits.
Encrypted cipher text: null
at org.bouncycastle.jcajce.provider.symmetric.util.BaseBlockCipher.engineInit(Unknown Source)
at javax.crypto.Cipher.init(Cipher.java:1346)
at javax.crypto.Cipher.init(Cipher.java:1282)
at Test.encryptString(Test.java:99)
at Test.main(Test.java:44)
And here is the relevant code that generates this exception:
public static byte[] iv = new SecureRandom().generateSeed(16);
public static void main(String[] args) {
String plainText = "Look mah, I'm a message!";
System.out.println("Original plaintext message: " + plainText);
// Initialize two key pairs
KeyPair keyPairA = generateECKeys();
KeyPair keyPairB = generateECKeys();
// Create two AES secret keys to encrypt/decrypt the message
SecretKey secretKeyA = generateSharedSecret(keyPairA.getPrivate(),
keyPairB.getPublic());
System.out.println(bytesToHex(secretKeyA.getEncoded()));
SecretKey secretKeyB = generateSharedSecret(keyPairB.getPrivate(),
keyPairA.getPublic());
System.out.println(bytesToHex(secretKeyB.getEncoded()));
// Encrypt the message using 'secretKeyA'
String cipherText = encryptString(secretKeyA, plainText);
System.out.println("Encrypted cipher text: " + cipherText);
// Decrypt the message using 'secretKeyB'
String decryptedPlainText = decryptString(secretKeyB, cipherText);
System.out.println("Decrypted cipher text: " + decryptedPlainText);
}
public static KeyPair generateECKeys() {
try {
ECNamedCurveParameterSpec parameterSpec = ECNamedCurveTable.getParameterSpec("secp521r1");
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(
"ECDH", "BC");
keyPairGenerator.initialize(parameterSpec);
KeyPair keyPair = keyPairGenerator.generateKeyPair();
System.out.println("Private key length: "
+ keyPair.getPrivate().getEncoded().length);
System.out.println("Public key length: "
+ keyPair.getPublic().getEncoded().length);
return keyPair;
} catch (NoSuchAlgorithmException | InvalidAlgorithmParameterException
| NoSuchProviderException e) {
e.printStackTrace();
return null;
}
}
public static SecretKey generateSharedSecret(PrivateKey privateKey,
PublicKey publicKey) {
try {
KeyAgreement keyAgreement = KeyAgreement.getInstance("ECDH", "BC");
keyAgreement.init(privateKey);
keyAgreement.doPhase(publicKey, true);
SecretKey key = keyAgreement.generateSecret("AES");
System.out.println("Shared key length: " + key.getEncoded().length);
return key;
} catch (InvalidKeyException | NoSuchAlgorithmException
| NoSuchProviderException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
}
public static String encryptString(SecretKey key, String plainText) {
try {
IvParameterSpec ivSpec = new IvParameterSpec(iv);
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "BC");
byte[] plainTextBytes = plainText.getBytes("UTF-8");
byte[] cipherText;
cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
cipherText = new byte[cipher.getOutputSize(plainTextBytes.length)];
int encryptLength = cipher.update(plainTextBytes, 0,
plainTextBytes.length, cipherText, 0);
encryptLength += cipher.doFinal(cipherText, encryptLength);
return bytesToHex(cipherText);
} catch (NoSuchAlgorithmException | NoSuchProviderException
| NoSuchPaddingException | InvalidKeyException
| InvalidAlgorithmParameterException
| UnsupportedEncodingException | ShortBufferException
| IllegalBlockSizeException | BadPaddingException e) {
e.printStackTrace();
return null;
}
}
public static String decryptString(SecretKey key, String cipherText) {
try {
Key decryptionKey = new SecretKeySpec(key.getEncoded(),
key.getAlgorithm());
IvParameterSpec ivSpec = new IvParameterSpec(iv);
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", "BC");
byte[] cipherTextBytes = hexToBytes(cipherText);
byte[] plainText;
cipher.init(Cipher.DECRYPT_MODE, decryptionKey, ivSpec);
plainText = new byte[cipher.getOutputSize(cipherTextBytes.length)];
int decryptLength = cipher.update(cipherTextBytes, 0,
cipherTextBytes.length, plainText, 0);
decryptLength += cipher.doFinal(plainText, decryptLength);
return new String(plainText, "UTF-8");
} catch (NoSuchAlgorithmException | NoSuchProviderException
| NoSuchPaddingException | InvalidKeyException
| InvalidAlgorithmParameterException
| IllegalBlockSizeException | BadPaddingException
| ShortBufferException | UnsupportedEncodingException e) {
e.printStackTrace();
return null;
}
}
public static String bytesToHex(byte[] data, int length) {
String digits = "0123456789ABCDEF";
StringBuffer buffer = new StringBuffer();
for (int i = 0; i != length; i++) {
int v = data[i] & 0xff;
buffer.append(digits.charAt(v >> 4));
buffer.append(digits.charAt(v & 0xf));
}
return buffer.toString();
}
public static String bytesToHex(byte[] data) {
return bytesToHex(data, data.length);
}
public static byte[] hexToBytes(String string) {
int length = string.length();
byte[] data = new byte[length / 2];
for (int i = 0; i < length; i += 2) {
data[i / 2] = (byte) ((Character.digit(string.charAt(i), 16) << 4) + Character
.digit(string.charAt(i + 1), 16));
}
return data;
}
I have a feeling that I'm not generating the ECDH keys properly (possibly due to the named curve that I chose), but otherwise, I'm stumped. Can anyone see where I may be doing something wrong?
EDIT: Almost forgot the rest of the output:
Original plaintext message: Look mah, I'm a message!
Private key length: 1106
Public key length: 158
Private key length: 1107
Public key length: 158
Shared key length: 66
0147A5780737C5C0D7457C503D4036AC7BBED53D5536A32D6BE8713E6DB4FE0A549AF20514C223D630426292A8EDB512EBD50726A130FFA4AEE96A0EC2A6F9D4C3A0
Shared key length: 66
0147A5780737C5C0D7457C503D4036AC7BBED53D5536A32D6BE8713E6DB4FE0A549AF20514C223D630426292A8EDB512EBD50726A130FFA4AEE96A0EC2A6F9D4C3A0

I've investigated this and I think it's a bug in the BC provider, or maybe two.
You can get your example to work if you choose a KDF-based algorithm and use an OID to identify the AES algorithm for the generated key:
...
KeyAgreement keyAgreement = KeyAgreement.getInstance(X9ObjectIdentifiers.dhSinglePass_stdDH_sha1kdf_scheme.getId(), "BC");
...
SecretKey key = keyAgreement.generateSecret(NISTObjectIdentifiers.id_aes128_CBC.getId());
...
Alternatively you could work around this by just truncating the original 66-byte SecretKey down to 16 (take the leading bytes, i.e. 0 thru 15), as this is what it should be doing but isn't.
We'll see what we can do about sorting this out in BC.

replace "BC" with new org.bouncycastle.jce.provider.BouncyCastleProvider() and remove NoSuchProviderException