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ECDH public and private keys generation with .Net C#

I am porting nodejs code to .Net and I am stuck at this part where I need to generate public and private keys.
Javascript code:
const dh = crypto.createECDH('prime256v1');
let privk = dh.getPrivateKey();
let pubk = dh.getPublicKey();
I tried the same with .Net C# with
var ecdh = new ECDiffieHellmanCng(CngKey.Create(CngAlgorithm.ECDiffieHellmanP256, null, new CngKeyCreationParameters { ExportPolicy = CngExportPolicies.AllowPlaintextExport }));
var privateKey = ecdh.Key.Export(CngKeyBlobFormat.EccPrivateBlob);
var publickey = ecdh.Key.Export(CngKeyBlobFormat.EccPublicBlob);
However when I tried to exchange those keys generated with C# with the Google FCM server, I got invalid argument error. When I copy the generated byte[] array from nodejs to .Net C# code as constants it works. It is obvious that generated keys are not meeting the requirement of the server. Since I am working with undocumented interface I can't tell why the keys are not accepted. I can see that the keys generated with nodejs are in 32 bytes in length for the private key and 65 bytes in length for the public key. The keys generated from C# are 140 and 96 bytes in length. How to generate keys in C# to match the key properties in nodejs?

I was able to solve my problem using Bouncy Castle
ECKeyPairGenerator gen = new ECKeyPairGenerator("ECDH");
SecureRandom secureRandom = new SecureRandom();
X9ECParameters ecp = NistNamedCurves.GetByName("P-256");
ECDomainParameters ecSpec = new ECDomainParameters(ecp.Curve, ecp.G, ecp.N, ecp.H, ecp.GetSeed());
ECKeyGenerationParameters ecgp = new ECKeyGenerationParameters(ecSpec, secureRandom);
gen.Init(ecgp);
AsymmetricCipherKeyPair eckp = gen.GenerateKeyPair();
ECPublicKeyParameters ecPub = (ECPublicKeyParameters)eckp.Public;
ECPrivateKeyParameters ecPri = (ECPrivateKeyParameters)eckp.Private;
byte[] publicKeyBytes = ecPub.Q.GetEncoded();

You can use ECDiffieHellman to encrypt messages. You have two options: Static-static ECDH and static-ephemeral ECDH:
For static-static ECDH the receiver will need to know the sender's public key (this might or might not be an option in your application). You should also have some data that is unique for this message (it might be a serial-number you get from somewhere else in the protocol or database-row or whatever or it might be a nonce). You then use ECDH to generate a secret key and use that to encrypt your data. This will give you your desired encrypted data length of 16 bytes, but it is not completely asymmetric: the encryptor is also able to decrypt the messages (again: this might or might not be a problem in your application).
Static-ephemeral is a bit different: here the encryptor generates a temporary (ephemeral) EC key pair. He then uses this key pair together with the receiver's public key to generate a secret key which can be used to encrypt the data. Finally, he sends the public key of the ephemeral key pair to the receiver together with the encrypted data. This might fit better into your application, but the complete encrypted data will now be 2*32+16=80 bytes using ECDH-256 and AES (as GregS notes you can save 32 bytes by only sending the x-coordinate of the public-key, but I do not believe that .NET exposes the functionality to recalculate the y-coordinate).
Here is a small class that will do static-static ECDH:
public static class StaticStaticDiffieHellman
{
private static Aes DeriveKeyAndIv(ECDiffieHellmanCng privateKey, ECDiffieHellmanPublicKey publicKey, byte[] nonce)
{
privateKey.KeyDerivationFunction = ECDiffieHellmanKeyDerivationFunction.Hash;
privateKey.HashAlgorithm = CngAlgorithm.Sha256;
privateKey.SecretAppend = nonce;
byte[] keyAndIv = privateKey.DeriveKeyMaterial(publicKey);
byte[] key = new byte[16];
Array.Copy(keyAndIv, 0, key, 0, 16);
byte[] iv = new byte[16];
Array.Copy(keyAndIv, 16, iv, 0, 16);
Aes aes = new AesManaged();
aes.Key = key;
aes.IV = iv;
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.PKCS7;
return aes;
}
public static byte[] Encrypt(ECDiffieHellmanCng privateKey, ECDiffieHellmanPublicKey publicKey, byte[] nonce, byte[] data){
Aes aes = DeriveKeyAndIv(privateKey, publicKey, nonce);
return aes.CreateEncryptor().TransformFinalBlock(data, 0, data.Length);
}
public static byte[] Decrypt(ECDiffieHellmanCng privateKey, ECDiffieHellmanPublicKey publicKey, byte[] nonce, byte[] encryptedData){
Aes aes = DeriveKeyAndIv(privateKey, publicKey, nonce);
return aes.CreateDecryptor().TransformFinalBlock(encryptedData,0, encryptedData.Length);
}
}
// Usage:
ECDiffieHellmanCng key1 = new ECDiffieHellmanCng();
ECDiffieHellmanCng key2 = new ECDiffieHellmanCng();
byte[] data = Encoding.UTF8.GetBytes("TestTestTestTes");
byte[] nonce = Encoding.UTF8.GetBytes("whatever");
byte[] encryptedData = StaticStaticDiffieHellman.Encrypt(key1, key2.PublicKey, nonce, data);
Console.WriteLine(encryptedData.Length); // 16
byte[] decryptedData = StaticStaticDiffieHellman.Decrypt(key2, key1.PublicKey, nonce, encryptedData);
Console.WriteLine(Encoding.UTF8.GetString(decryptedData));

String encryption in Objective-C decrypt in C#

I am building a iPhone app which uses a c# web service. My iPhone app takes in some data and encrypts it and passes it to the web service. How do I decrypt the data in C#?
My iPhone app contains the following code:
NSString *pString = #"Some string to be encoded";
NSString *key = #"My encryption key";
NSData *pData = [pString dataUsingEncoding:NSUTF8StringEncoding];
pData = [pData AES256EncryptWithKey:key];
NSString *pID = [pData base64EncodedStringWithOptions:NSDataBase64Encoding76CharacterLineLength];
EDIT: The data is already stored in the web service so I can't readily change the encryption approach. The C# application is not on the server so there is no possibility of compromising the key.
I have tried the following C# code to decrypt the data:
static string DecryptString(string encryptedText, string key)
{
byte[] encryptedString = Convert.FromBase64String(encryptedText);
byte[] encryptionKey = Encoding.UTF8.GetBytes(key.Substring(0, 32));
using (var provider = new AesCryptoServiceProvider())
{
provider.Mode = CipherMode.CBC;
provider.Padding = PaddingMode.PKCS7;
provider.Key = encryptionKey;
using (var ms = new MemoryStream(encryptedString))
{
// Read the first 16 bytes which is the IV.
byte[] iv = new byte[16];
ms.Read(iv, 0, 16);
provider.IV = iv;
using (var decryptor = provider.CreateDecryptor())
{
using (var cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
{
using (var sr = new StreamReader(cs))
{
return sr.ReadToEnd();
}
}
}
}
}
}
However, I get the following exception:
System.Security.Cryptography.CryptographicException was unhandled
HResult=-2146233296 Message=Padding is invalid and cannot be
removed.
The encryptedText received by DecryptString is 80 bytes in length.

The sample ObjC code uses by default CBC modem, PKCS#7 padding and a default iv of 16 0x00 bytes.
The C# also uses CBC mode and PKCS#7 padding. The decryption code expects a 16-byte iv pre-pended to the encrypted data and that does not exist.
byte[] iv = new byte[16];
ms.Read(iv, 0, 16);
provider.IV = iv;
This needs to be changed so that iv is set to an array of 16 0x00 bytes and the ms.Read(iv, 0, 16) statement needs to be deleted so the decrypt function gets all of the encrypted data.
Notes:
Using a devault anything in encryption is a bad idea, always provide the correect length data.
Authentication of the encrypted data needs should be added so that it can be determined if there an incorrect key or the data has been tampered with.
There really should be a version number and a random IV used and prepended to the encrypted so you should really consider correcting this. This demonstrates why a version number generally needs to be provided and used.
RNCryptor covers the above issues.
The handling of the encryption key also needs to be considered so that is is as secure as necessary.

You need to first decode the base-64 encoded string to a byte[] - see Convert.FromBase64String(). Then you need to use the Aes class to decrypt it - there's an example on its documentation page.

Encrypt in Coldfusion and decrypt in C#

Here is the code used to encrypt in coldfusion
<cfset strBase64Value = encrypt(strValue,24 character key,AES) />
It is generating encrypted values like 714FEA9A9A2184769CA49D5133F08580 which seems odd to me considering it is only uppercase and numbers.
What C# library should I use to properly decrypt it ?
Also looking at this information, it seems that by default it uses the UUEncode algorithm to encode.
Should I ask the encrypter to use Base64 as encoding parameter ?

It is generating encrypted values like 714FEA9A9A2184769CA49D5133F08580
Then they are using "Hex", not the default "UUEncode". Either "hex" or "base64" is fine. As long as you both agree upon the encoding, it does not really matter.
You can use RijndaelManaged to decrypt the strings. However, the default encryption settings for ColdFusion and C# differ slightly. With the encrypt function:
"AES" is short for "AES/ECB/PKCS5Padding"
"ECB" mode does not use an IV
Key strings are always base64 encoded
NB: Despite the name difference, for the SUN provider, PKCS5Padding (CF/Java) corresponds to PaddingMode.PKCS7 (C#). As mentioned in this thread, the "... SUN provider in Java indicate[s] PKCS#5 where PKCS#7 should be used - "PKCS5Padding" should have been "PKCS7Padding". This is a legacy from the time that only 8 byte block ciphers such as (triple) DES symmetric cipher were available."
So you need to ensure your C# settings are adjusted to match. With that in mind, just decode the encrypted text from hex and the key string from base64. Using the slightly ugly example in the API, just adjust the algorithm settings to match those used by the encrypt() function:
Encrypt with ColdFusion
<cfscript>
plainText = "Nothing to see";
// 128 bit key base64 encoded
keyInBase64 = "Y25Aju8H2P5DR8mY6B0ezg==";
// "AES" is short for "AES/ECB/PKCS5Padding"
encryptedText = encrypt(plainText, keyInBase64, "AES", "hex");
WriteDump( encryptedText );
// result: 8889EDF02F181158AAD902AB86C63951
</cfscript>
Decrypt with C#
byte[] bytes = SomeMethodToConvertHexToBytes( encryptedText );
byte[] key = Convert.FromBase64String( keyInBase64 );
string decryptedText = null;
using (RijndaelManaged algorithm = new RijndaelManaged())
{
// initialize settings to match those used by CF
algorithm.Mode = CipherMode.ECB;
algorithm.Padding = PaddingMode.PKCS7;
algorithm.BlockSize = 128;
algorithm.KeySize = 128;
algorithm.Key = key;
ICryptoTransform decryptor = algorithm.CreateDecryptor();
using (MemoryStream msDecrypt = new MemoryStream(bytes))
{
using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
{
using (StreamReader srDecrypt = new StreamReader(csDecrypt))
{
decryptedText = srDecrypt.ReadToEnd();
}
}
}
}
Console.WriteLine("Encrypted String: {0}", encryptedText);
Console.WriteLine("Decrypted String: {0}", decryptedText);
Keep in mind you can (and probably should) adjust the settings, such as using the more secure CBC mode instead of ECB. You just need to coordinate those changes with the CF developer.

If anyone had similar problem with JAVA I just implemented encryption and decryption of string previously encrypted/decrypted in coldfusion with "Hex" and "tripledes". Here is my code:
private static final String PADDING = "DESede/ECB/PKCS5Padding";
private static final String UTF_F8 = "UTF-8";
private static final String DE_SEDE = "DESede";
private String secretKey;
public String encrypt(String message) throws Exception {
secretKey = getSecretKey();
final byte[] secretBase64Key = Base64.decodeBase64(secretKey);
final SecretKey key = new SecretKeySpec(secretBase64Key, DE_SEDE);
final Cipher cipher = Cipher.getInstance(PADDING);
cipher.init(Cipher.ENCRYPT_MODE, key);
final byte[] plainTextBytes = message.getBytes();
final byte[] cipherText = cipher.doFinal(plainTextBytes);
return Hex.encodeHexString(cipherText);
}
public String decrypt(String keyToDecrypt) throws Exception {
secretKey = getSecretKey();
byte[] message = DatatypeConverter.parseHexBinary(keyToDecrypt);
final byte[] secretBase64Key = Base64.decodeBase64(secretKey);
final SecretKey key = new SecretKeySpec(secretBase64Key, DE_SEDE);
final Cipher decipher = Cipher.getInstance(PADDING);
decipher.init(Cipher.DECRYPT_MODE, key);
final byte[] plainText = decipher.doFinal(message);
return new String(plainText, UTF_F8);
}

RSA encryption from Flex client and Corresponding Decryption from Web service

I'm having a problem setting up RSA encryption/decryption mechanism between flex client and web service written in c#. The idea is this: I'll encrypt some text from flex and then decrypt it from web service. I'm using as3crypto library from google. It is encrypting/decrypting text properly. I also have the code on the web service side to encrypt/decrypt properly. My problem is synchronizing them - basically sharing the public key to flex and keeping the private key to the web service.
My flex "encrypt" function takes modulus and exponent of RSA to do text encryption, so how do i get these modulus and exponent attributes from the web service's RSACryptoServiceProvider, so they speak the same standard.
I tried the
RSAKeyInfo.Modulus
RSAKeyInfo.Exponent
from the web service and fed them to the flex client.
After doing encryption on flex I took the cipher text and fed it to decrypt method on web service, but it is giving me "bad data" error message.
System.Security.Cryptography.CryptographicException: Bad Data.
at System.Security.Cryptography.CryptographicException.ThrowCryptogaphicException(Int32 hr)
at System.Security.Cryptography.Utils._DecryptKey(SafeKeyHandle hPubKey, Byte[] key, Int32 dwFlags)
at System.Security.Cryptography.RSACryptoServiceProvider.Decrypt(Byte[] rgb, Boolean fOAEP)
at Microsoft.Samples.Security.PublicKey.App.RSADecrypt(Byte[] DataToDecrypt, RSAParameters RSAKeyInfo, Boolean DoOAEPPadding) in C:\Users
\Me\Desktop\After Release\5-24-2011-webServiceCrypto\publickeycryptography\CS\PublicKeyCryptography\PublicKey.cs:line 219
Encryption failed.
How do i make sure they are both using the same byte 64 or 128 byte encryption . ie the input from flex should fit to what is expected by the web service RSACryptoServiceProvider's decrypt method.
(I'm assuming the size might be a problem, may be it's not - i'm lost)
Here is the code, first flex client followed by web service c# code
private function encrypt():void {
var rsa:RSAKey = RSAKey.parsePublicKey(getModulus(), getExponent());
trace("Modulus Lenght: " + getModulus().length);
trace("Exponent Lenght : " + getExponent().length);
var data:ByteArray = getInput(); //returns byteArray of plainText
var dst:ByteArray = new ByteArray;
rsa.encrypt(data, dst, data.length);
trace("Enc Data: " + dst.toString() );
currentResult = Hex.fromArray(dst);
encryptedText = currentResult;
trace("Encrypted:: " + currentResult);
}
//For testing purposes
private function decrypt():void {
var rsa:RSAKey = RSAKey.parsePrivateKey(getModulus(), getExponent(), getPrivate(), getP(), getQ(), getDMP1(), getDMQ1(), getCoeff());
var data:ByteArray = Hex.toArray(encryptedText);
trace("Byte array: " + data.toString());
var dst:ByteArray = new ByteArray;
rsa.decrypt(data, dst, data.length);
decryptedText = Hex.fromArray(dst);
trace("Decrypted text: " + Hex.toString(decryptedText));
}
And web service part is as follows:
try
{
//Create a UnicodeEncoder to convert between byte array and string.
UnicodeEncoding ByteConverter = new UnicodeEncoding();
//Create byte arrays to hold original, encrypted, and decrypted data.
byte[] dataToEncrypt = ByteConverter.GetBytes("Data to Encrypt");
byte[] encryptedData;
byte[] decryptedData;
//Create a new instance of RSACryptoServiceProvider to generate
//public and private key data.
using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
{
//Pass the data to ENCRYPT, the public key information
//(using RSACryptoServiceProvider.ExportParameters(false),
//and a boolean flag specifying no OAEP padding.
encryptedData = RSAEncrypt(dataToEncrypt, RSA.ExportParameters(false), false);
//Pass the data to DECRYPT, the private key information
//(using RSACryptoServiceProvider.ExportParameters(true),
//and a boolean flag specifying no OAEP padding.
decryptedData = RSADecrypt(encryptedData, RSA.ExportParameters(true), false);
//Display the decrypted plaintext to the console.
Console.WriteLine("\n\nDecrypted plaintext: {0}", ByteConverter.GetString(decryptedData));
}
}
static public byte[] RSAEncrypt(byte[] DataToEncrypt, RSAParameters RSAKeyInfo, bool DoOAEPPadding)
{
try
{
byte[] encryptedData;
//Create a new instance of RSACryptoServiceProvider.
using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
{
//Import the RSA Key information. This only needs
//toinclude the public key information.
RSA.ImportParameters(RSAKeyInfo);
//Encrypt the passed byte array and specify OAEP padding.
//OAEP padding is only available on Microsoft Windows XP or
//later.
encryptedData = RSA.Encrypt(DataToEncrypt, DoOAEPPadding);
}
return encryptedData;
}
//Catch and display a CryptographicException
//to the console.
catch (CryptographicException e)
{
Console.WriteLine(e.Message);
return null;
}
}
static public byte[] RSADecrypt(byte[] DataToDecrypt, RSAParameters RSAKeyInfo, bool DoOAEPPadding)
{
try
{
Console.WriteLine("Modulus Lenghth :" + RSAKeyInfo.Modulus.Length);
Console.WriteLine("Exponent Length :" + RSAKeyInfo.Exponent.Length);
byte[] decryptedData;
//Create a new instance of RSACryptoServiceProvider.
using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
{
//Import the RSA Key information. This needs
//to include the private key information.
RSA.ImportParameters(RSAKeyInfo);
//Decrypt the passed byte array and specify OAEP padding.
//OAEP padding is only available on Microsoft Windows XP or
//later.
decryptedData = RSA.Decrypt(DataToDecrypt, DoOAEPPadding);
}
return decryptedData;
}
//Catch and display a CryptographicException
//to the console.
catch (CryptographicException e)
{
Console.WriteLine(e.ToString());
return null;
}
}
I'm not quite sure if this RSA set up is the way to go...
Any kinda comment / advice/ or recommended solution is welcome,
thanks guys

Eureka! Eureka! I got it.
The problem was after decryption from web service, the encrypted byte array missed 0's in between, so that when changed to string it gets unreadable '????????' text. So I just put paddWithZeros() function to pad the decrypted byte array with 0's between bytes and it worked.
Thanks Kevin, your solution gave me an insight into what things I should consider. So during decrypting I specify parameter fOAEP as false, so it would use PKCS#1 for padding (making both libraries use the same standard).
RSA.Decrypt(DataToDecrypt, DoOAEPPadding); // DoOAEPPadding = false
another error that i was getting is Bad Data exception. This was fixed when i shared the RSA cryptoServiceProvider's parameters (modulus and exponent) to actionScript methods.
I also changed the byte[] array of c# RSA attributes (like Modulus n, Exponent e, Private d..etc) to hexa string so that I'd be able to share with as3crypto library.
I'd love to share what worked for me; save others some time.
<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">
<fx:Script>
<![CDATA[
import com.hurlant.crypto.Crypto;
import com.hurlant.crypto.rsa.RSAKey;
import com.hurlant.crypto.symmetric.ICipher;
import com.hurlant.crypto.symmetric.IPad;
import com.hurlant.util.Hex;
private var currentResult:String;
private var encryptedText:String;
private var decryptedText:String;
private function encrypt(plainText:String):String {
var rsa:RSAKey = RSAKey.parsePublicKey(getModulus(), getExponent());
var data:ByteArray = Hex.toArray(Hex.fromString(plainText)); //returns byteArray of plainText
var dst:ByteArray = new ByteArray;
rsa.encrypt(data, dst, data.length);
currentResult = Hex.fromArray(dst);
encryptedText = currentResult;
trace ("Cipher: " + currentResult);
return currentResult;
}
private function getInput():ByteArray {
return null;
}
private function getModulus():String {
return "b6a7ca9002b4df39af1ed39251a5d"; //read this value from web service.
}
private function getExponent():String {
return "011"; //read this value from web service.
}
//For debugging and testing purposes
// private function decrypt(cipherText:String):String {
// var rsa:RSAKey = RSAKey.parsePrivateKey(getModulus(), getExponent(), getPrivate(), getP(), getQ(), getDMP1(), getDMQ1(), getCoeff());
// var data:ByteArray = Hex.toArray(cipherText);
// var dst:ByteArray = new ByteArray;
// rsa.decrypt(data, dst, data.length);
// decryptedText = Hex.fromArray(dst);
//trace('decrypted : ' + decryptedText);
// return Hex.toString(decryptedText);
// }
]]>
</fx:Script>
<fx:Declarations>
<!-- Place non-visual elements (e.g., services, value objects) here -->
</fx:Declarations>
<mx:VBox >
<s:Button label="Encrypt Text" click="encrypt('my plain text')" />
<s:Button label="Decrypt Text" click="decrypt({encryptedText})" />
</mx:VBox>
</s:Application>
And the web service part of decryption looks like this:
static public string RSADecrypt(string cipherText)
{
UnicodeEncoding ByteConverter = new UnicodeEncoding();
byte[] DataToDecrypt = StringToByteArray(cipherText);
bool DoOAEPPadding = false;
try
{
byte[] decryptedData;
using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
{
KeyInfo keyInfo = new KeyInfo();
RSAParameters RSAKeyInfo = keyInfo.getKey();
RSA.ImportParameters(RSAKeyInfo);
decryptedData = RSA.Decrypt(DataToDecrypt, DoOAEPPadding);
}
byte[] paddedOutput = paddWithZeros(decryptedData); //to sync with as3crypto
return (ByteConverter.GetString(paddedOutput));
}catch (CryptographicException e)
{
//handle error
return null;
}
}
I'll do some reading about padding schemes for RSA, see if there is any misconception.
Thanks

Seems overly complicated. I've worked on some high security systems before, but this is ludicrous. Why would you need this kind of level of encryption at the text being sent unless you don't want the user to know the text he just inputted?
Just use a strong SSL key (256bit is max for IE6, you could use 512 but only compatible with newer browsers) for the actual transfer protocol (I imagine HTTP) with a binary data format (AMF) and everything should be fine. I doubt your system is that important to leverage the use of encrypting text.

I use as3crypto and JAVA web-services. Here are some thoughts:
a. I generated my public and private RSA keys via openssl
b. My client loads the public .cer file at application startup (if you just hardcoded them in from the generated key that works too).
var pemString : String = new String(data.target.data);
var x509Cert : X509Certificate = new X509Certificate(pemString);
var publicRSAKey : RSAKey = x509Cert.getPublicKey();
c. Encrypt my strings via
var inputByteArray : ByteArray = Hex.toArray(Hex.fromString(inputString));
var outputByteArray : ByteArray = new ByteArray();
appSettingsModel.publicRSAKey.encrypt(inputByteArray, outputByteArray, inputByteArray.length);
d. I didn't write the JAVA side of things but you aren't using JAVA anyways. I know that as3crypto uses PKCS1 padding by default:
RSAKEY.as
private function _encrypt(op:Function, src:ByteArray, dst:ByteArray, length:uint, pad:Function, padType:int):void {
// adjust pad if needed
if (pad==null) pad = pkcs1pad;
This can be changed but I haven't tried it yet. Based on your code it looks like you might be trying to decrypt with OAEP scheme, but I can't tell how you are setting that bool. You may want to take a look at what padding scheme is being used with the bool as false and try to change one side or the other to match padding strategies.

How to make this: J2ME encrypt C# decrypt And J2ME decrypt C# encrypt?

C#
string keystr = "0123456789abcdef0123456789abcdef";
string plainText = "www.bouncycastle.org";
RijndaelManaged crypto = new RijndaelManaged();
crypto.KeySize = 128;
crypto.Mode = CipherMode.CBC;
crypto.Padding = PaddingMode.PKCS7;
crypto.Key = keystr.ToCharArray().Select(c=>(byte)c).ToArray();
// get the IV and key for writing to a file
byte[] iv = crypto.IV;
byte[] key = crypto.Key;
// turn the message into bytes
// use UTF8 encoding to ensure that Java can read in the file properly
byte[] plainBytes = Encoding.UTF8.GetBytes(plainText.ToCharArray());
// Encrypt the Text Message using AES (Rijndael) (Symmetric algorithm)
ICryptoTransform sse = crypto.CreateEncryptor();
MemoryStream encryptedFs = new MemoryStream();
CryptoStream cs = new CryptoStream(encryptedFs, sse, CryptoStreamMode.Write);
try
{
cs.Write(plainBytes, 0, plainBytes.Length);
cs.FlushFinalBlock();
encryptedFs.Position = 0;
string result = string.Empty;
for (int i = 0; i < encryptedFs.Length; i++)
{
int read = encryptedFs.ReadByte();
result += read.ToString("x2");
}
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
finally
{
encryptedFs.Close();
cs.Close();
}
}
Java:
private String key = "0123456789abcdef0123456789abcdef";
private String plainText = "www.bouncycastle.org";
cipherText = performEncrypt(Hex.decode(key.getBytes()), plainText);
private byte[] performEncrypt(byte[] key, String plainText)
{
byte[] ptBytes = plainText.getBytes();
final RijndaelEngine rijndaelEngine = new RijndaelEngine();
cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(rijndaelEngine));
String name = cipher.getUnderlyingCipher().getAlgorithmName();
message("Using " + name);
byte[]iv = new byte[16];
final KeyParameter keyParameter = new KeyParameter(key);
cipher.init(true, keyParameter);
byte[] rv = new byte[cipher.getOutputSize(ptBytes.length)];
int oLen = cipher.processBytes(ptBytes, 0, ptBytes.length, rv, 0);
try
{
cipher.doFinal(rv, oLen);
}
catch (CryptoException ce)
{
message("Ooops, encrypt exception");
status(ce.toString());
}
return rv;
}
C# produces: ff53bc51c0caf5de53ba850f7ba08b58345a89a51356d0e030ce1367606c5f08
java produces: 375c52fd202696dba679e57f612ee95e707ccb05aff368b62b2802d5fb685403
Can somebody help me to fix my code?

In the Java code, you do not use the IV.
I am not savvy enough in C# to help you directly, but I can give some information.
Rijndael, aka "the AES", encrypts blocks of 16 bytes. To encrypt a long message (e.g. your test message, when encoding, is 20 bytes long), Rijndael must be invoked several times, with some way to chain the invocations together (also, there is some "padding" to make sure that the input length is a multiple of 16). The CBC mode performs such chaining.
In CBC, each block of data is combined (bitwise XOR) with the previous encrypted block prior to being itself encrypted. Since the first block of data has no previous block, we add a new conventional "zero-th block" called the IV. The IV should be chosen as 16 random bytes. The decrypting party will need the IV. The IV needs not be secret (that's the difference between the IV and the key) so it is often transmitted along the message.
In your Java code, you do not specify the IV, you just create a variable called iv and do not use it. So the Rijndael implementation is on its own for that. Chances are that it generated a random IV. Similarly, you do not give an IV to the Rijndael implementation in the C# code. So it is quite plausible that there again a random IV was selected. But not the same than the one in the Java code, hence the distinct results.
(Note: you 20-byte input string is padded to 32 bytes. You give two "results" in hexadecimal, of length 32 bytes each. This is coherent but means that those results do not include the IV -- otherwise they would be 48-byte long.)

I think the algorithm is built in slighty different way and/or the salt key is interpered in different way.