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Problem with encryption and decryption with AES-gcm 128 using C# .NET framework

I am trying to work with Encryption and Decryption using AES-gcm 128 bits using C# .NET Framework. But I could not find any good solutions with this problem. I have just found on this website, someone recommends to use Bouncy castle library.
I have no ideas, if Bouncy castle is supported AES-gcm 128. And I sill don't know how to input this library in .NET framework.
Could anyone resolve this problem for me? I am a newbie so I really need your helps.
Thank you so much!!!

AES GCM 256 Runs in framework 5 and above... So, first write the program with framework 5 and above I have written a sample class to use it and the library using System.Security.Cryptography; I have added to this class
internal class class_Encrypt_Decrypt_AES_GCM
{
public byte[] Encrypt(String key, string payload, byte[] header_aad, byte[] tag)
{
byte[] cipherText = new byte[payload.Length];
try
{
//string key = "a05e19dc2682a72a8a9fe3d70707393e";Example
// string payload = "Hello";Example
// byte[] tag = new byte[16];Example
// byte[] header_aad = { 0x5a, 0xa5, 0x0, 0x6, 0x1a };Example
int payload_len = payload.Length;
byte[] bytes_key = Encoding.ASCII.GetBytes(key);
byte[] bytes_IV = new byte[16];
byte[] send_IV = new byte[12];
bytes_IV = IV_generator();
byte[] bytes_payload = new byte[payload.Length];
byte[] bytes_payload1 = Encoding.ASCII.GetBytes(payload);
Array.Copy(bytes_payload1, bytes_payload, bytes_payload1.Length);
Array.Copy(bytes_IV, send_IV, bytes_IV.Length - 4);
int num = payload.Length;
header_aad[3] = (byte)(num & 0xff);
//----------hi byte
header_aad[2] = (byte)(num >> 8 & 0xff);
//==========================================
AesGcm aesGcm = new AesGcm(bytes_key);
aesGcm.Encrypt(send_IV, bytes_payload, cipherText, tag, header_aad);
// String IV_STR = Convert.ToString(send_IV);
// String key_STR = Convert.ToString(bytes_key);
// String RES = Convert.ToString(cipherText);
//example for Decoder
// aesGcm.Decrypt(send_IV, cipherText, tag, bytes_payload, header_aad);
// string result = ASCIIEncoding.UTF8.GetString(bytes_payload);
}
catch (Exception e2)
{
int b = 0;
}
return cipherText;
}
private byte[] IV_generator()
{
byte[] byte_IV = new byte[16];
Random rnt = new Random(DateTime.Now.Day);
byte[] byte_time_rnd = new byte[16];
rnt.NextBytes(byte_time_rnd);
byte[] byet_sha384_date;
SHA384 shaM = new SHA384Managed();
byet_sha384_date = shaM.ComputeHash(Encoding.ASCII.GetBytes(DateTime.Now.Date.ToString()));
for (int i = 0; i < byte_time_rnd.Length; i++)
{
byte_IV[i] = (byte)(byet_sha384_date[i] ^ byte_time_rnd[i]);
}
return byte_IV;
}
In this class, there is also a function for making IV, in which I have used time parameters

ECDiffieHellmanPublicKey from ByteArray (using ECDiffieHellman NamedCurves)

I'm working on communication nodejs -> c# server.
I need to secure connection between them so I chode ECDiffieHellman as the key exchange mechanism (nodejs supports it). I had some problem with it... Just my lack of knowledge so I've made my lesson and now I can generate and export keys as base64 and nodejs have no problem with accepting c# key but on the other side c# ... won't even take his own key ...
error System.Security.Cryptography.CryptographicException: 'The parameter is incorrect.'
Ye I know I'm making sth wrong but what?
using (ECDiffieHellman alice = ECDiffieHellman.Create(ECCurve.NamedCurves.brainpoolP256r1))
{
var alicePublicKey = Convert.ToBase64String(alice.PublicKey.ToByteArray());
//NODEJS brainpoolP256r1 publickey
var key1 = Convert.FromBase64String("BB92GQLod55fXEhgNxwQcPQFFvph7eIjnSzdNz2PhzUAOcaPEiLBPQR6AL5pqVLFram8OtPapoBGYZn2vaGl+/U=").ToList();
//test
var key2 = Convert.FromBase64String(alicePublicKey);
var keyType = new byte[] { 0x45, 0x43, 0x4B, 0x50 };
var keyLength = new byte[] { 0x20, 0x00, 0x00, 0x00 };
key1.RemoveAt(0);
key1 = keyType.Concat(keyLength).Concat(key1).ToList();
byte[] bobKeyBytes = key1.ToArray();
ECDiffieHellmanPublicKey k = ECDiffieHellmanCngPublicKey.FromByteArray(bobKeyBytes, new CngKeyBlobFormat("ECCPUBLICBLOB")); //error System.Security.Cryptography.CryptographicException: 'The parameter is incorrect.'
ECDiffieHellmanPublicKey kk = ECDiffieHellmanCngPublicKey.FromByteArray(key2, new CngKeyBlobFormat("ECCPUBLICBLOB")); // error System.Security.Cryptography.CryptographicException: 'The parameter is incorrect.'
byte[] aliceKey = alice.DeriveKeyMaterial(k);
byte[] encryptedMessage = null;
byte[] iv = null;
// Send(aliceKey, "Secret message", out encryptedMessage, out iv);
}
you can find rest of the story there
ECDH nodejs and C# key exchange

You're asserting that the base64 contents that go into key1 are for brainpoolP256r1.
Decoding the value we see that it's a 65 byte payload starting with 04, which looks like an uncompressed point encoding for a curve with a 256-bit prime. So far so good.
You've even correctly used BCRYPT_ECDH_PUBLIC_GENERIC_MAGIC, but you can't import a "generic named key blob" without specifying the import property that tells it which curve.
The easy way that you load the key from this point is
byte[] keyX = new byte[key1.Length / 2];
byte[] keyY = new byte[keyX.Length];
Buffer.BlockCopy(key1, 1, keyX, 0, keyX.Length);
Buffer.BlockCopy(key1, 1 + keyX.Length, keyY, 0, keyY.Length);
ECParameters parameters = new ECParameters
{
Curve = ECCurve.NamedCurves.brainpoolP256r1,
Q =
{
X = keyX,
Y = keyY,
},
};
byte[] derivedKey;
using (ECDiffieHellman bob = ECDiffieHellman.Create(parameters))
using (ECDiffieHellmanPublicKey bobPublic = bob.PublicKey)
{
derivedKey = alice.DeriveKeyFromHash(bobPublic, HashAlgorithmName.SHA256);
}
I've gone ahead and expanded the DeriveKeyMaterial method into what it means by default with an ECDiffieHellmanCng, since other types of ECDH don't support that method (due to its low specificity of behavior).

C# and Java DES Encryption value are not identical

I am trying to encrypt the same data using C# and Java. If the data is more than 7 bytes then Java and C#'s encrypted value are not identical.
Input 1: a
java output: FrOzOp/2Io8=
C# output: FrOzOp/2Io8=
Input 2: abc
j : H9A/ahl8K7I=
c#: H9A/ahl8K7I=
Input 3: aaaaaaaa (Problem)
j : Gxl7e0aWPd7j6l7uIEuMxA==
c#: Gxl7e0aWPd7sf1xR6hK4VQ==
Here is the implementation of C# and Java methods.
C# code:
public String saltTxt = "12345678";
public String Encrypt(String txt)
{
byte[] data = Encrypt(Encoding.UTF8.GetBytes(txt));
DESCryptoServiceProvider alg = new DESCryptoServiceProvider();
alg.Key = Encoding.UTF8.GetBytes(saltTxt.ToCharArray(), 0, cprovider.KeySize / 8);
alg.IV = new byte[8];
MemoryStream ms = new MemoryStream();
CryptoStream stem = new CryptoStream( ms, cprovider.CreateEncryptor(),CryptoStreamMode.Write);
stem.Write(txt, 0, txt.Length);
stem.FlushFinalBlock();
data = ms.ToArray();
return Convert.ToBase64String(data);
}
Java Code:
public String saltTxt = "12345678";
public String Encrypt(String str) {
try {
KeySpec myKey = new DESKeySpec(saltTxt.getBytes("UTF8"));
SecretKey key = SecretKeyFactory.getInstance("DES").generateSecret(myKey);
Cipher ecipher = Cipher.getInstance("DES");
ecipher.init(Cipher.ENCRYPT_MODE, key);
byte[] data = str.getBytes("UTF8");
byte[] crypt = ecipher.doFinal(data);
return new BASE64Encoder().encode(crypt);
} catch (Exception ex) {
}
return null;
}
Any idea why it's not working as expected?

The problem was in mode of encryption.
SunJCE provider uses ECB as the default mode, and PKCS5Padding as the default padding scheme for DES, DES-EDE and Blowfish ciphers. (JCA Doc)
and
In .Net, The default operation mode for the symmetric algorithm is CipherMode.CBC and default padding is PaddingMode.PKCS7. (msdn..SymmetricAlgorithm)
The following changes resolve the problem.
// in C#
DESCryptoServiceProvider alg = new DESCryptoServiceProvider();
alg.Mode = CipherMode.ECB; // specified
or
// in java
chiper = Cipher.getInstance("DES/CBC/PKCS5Padding");
don't change in both sides.

You're probably seeing ISO 10126 padding, which appends random bytes to the plaintext to fill it up t oa multiple of the block size.
This behavior is by design.

The code (Java/Android) bellow worke for me.
I used the same approach on C#.
public static String Cripto(String Password)
{
String PasswordCripto = "";
try
{
String encryptionKey = "anyEncryptionString";
MessageDigest messageDigest = MessageDigest.getInstance("MD5");
messageDigest.update(encryptionKey.getBytes("UTF-8"), 0, encryptionKey.length());
byte[] encryptionKeyBytes = messageDigest.digest();
SecretKeySpec Key = new SecretKeySpec(encryptionKeyBytes,"DESede");
Cipher cipher = Cipher.getInstance("DESEDE/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, Key);
byte[] encryptedBytes = cipher.doFinal(Password.getBytes("UTF-8"));
PasswordCripto = new String(Base64.encode(encryptedBytes, Base64.DEFAULT), "UTF-8");
} catch(Exception e) { }
return PasswordCripto ;
}

Bouncy Castle Not Decrypting DoFinal from Java in C#

I am trying to decrypt data that is encrypted using the Bouncy Castle library in Java with a C#. The data that is encrypted in Java (again with the Bouncy Castle Libraries) can be decrypted with Java. I am using the same keys and parameters but when I reach DoFinal I get the error "pad block corrupted".
Here is the Java:
KeyParameter keyParam = new KeyParameter(key);
CipherParameters param = new ParametersWithIV(keyParam, initVector);
BlockCipherPadding padding = new PKCS7Padding();
BufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(new AESEngine()), padding);
cipher.reset();
cipher.init(true, param);
byte[] fileBytes = Base64.decodeBase64(decryptedStringData);
byte[] encrypted = new byte[cipher.getOutputSize(fileBytes.length)];
int l = cipher.processBytes(fileBytes, 0, fileBytes.length, encrypted, 0);
l += cipher.doFinal(encrypted, l);
return (Base64.encodeBase64String(encrypted));
Here is the C#:
KeyParameter keyParam = new KeyParameter(key);
ICipherParameters param = new ParametersWithIV(keyParam, initVector);
IBlockCipherPadding padding = new Pkcs7Padding();
BufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new CbcBlockCipher(new AesEngine()), padding);
cipher.Reset();
cipher.Init(false, param);
byte[] fileBytes = Convert.FromBase64String(encryptedDataString);
byte[] decrypted = new byte[cipher.GetOutputSize(fileBytes.Length)];
int l = cipher.ProcessBytes(fileBytes, 0, fileBytes.Length, decrypted, 0);
l += cipher.DoFinal(decrypted, l);
return(Convert.ToBase64String(decrypted));
I am generating a 32 byte PBK for the key based on a hash that has been buffered... however, we checked the key generated between Java and C# and they are the same.

It turns out that the data provided for encryption and decryption were encoded in different formats. I was pulling in UTF-8 encoded strings to decrypt and they needed to be made into Base64 strings first. Thanks for all of the help provided.

C# RSA public Modulus/Exponent? (Bad Data)

I have tried and tried but I continue to get "Bad Data". How do you decrypt data using the RSACryptoServiceProvider with the public key's Exponent/Modulus?
public static byte[] Encrypt(byte[] b, byte[] mod, byte[] exp)
{
CspParameters csp = new CspParameters();
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(csp);
RSACryptoServiceProvider.UseMachineKeyStore = false;
RSAParameters par = new RSAParameters();
par.Exponent = exp;
par.Modulus = mod;
rsa.ImportParameters(par);
return rsa.Encrypt(b, false);
}
public static byte[] Decrypt(byte[] b, byte[] pubexp, byte[] mod, byte[] priexp)
{
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
RSACryptoServiceProvider.UseMachineKeyStore = false;
RSAParameters rp = new RSAParameters();
rp.Exponent = pubexp;
rp.D = priexp;
rp.Modulus = mod;
rsa.ImportParameters(rp);
return rsa.Decrypt(b, false);
}
static List<byte[]> Base2Array(string str)
{
byte[] b = Convert.FromBase64String(str);
List<byte[]> Bytes = new List<byte[]>();
int i = 0;
while (i < b.Length)
{
int size = IPAddress.NetworkToHostOrder(BitConverter.ToInt32(b, i));
i += 4;
byte[] b2 = new byte[size];
Array.Copy(b, i, b2, 0, size);
Bytes.Add(b2);
i += size;
}
return Bytes;
}
static void Main(string[] args)
{
List<byte[]> pub = Base2Array("AAAAB3NzaC1yc2EAAAABJQAAAIBMW4HxU1glv+CcZpJnvUKEyeNfFoKkyLOVLOOb/vNXQkrkGsNdpYAZkKKizij8fD3u3/iYT8UI+xkFoyonRYVipgCslirJB1VdvLivXs69Ht4vf7VAv2yJSUni3XsIHauMlfOkjJ7DpUW75ZkrxsGieICFWlXvRnAyDdqQrkZRZQ==");
List<byte[]> pri = Base2Array("AAAAgBSjHDNiojO3UXZg6Ux4VyrOx9SCn9mCWgykWTEUeR6Anp6DxhlPUw3UEEetVy97hlw8iGCEQxcvG4T7qocni9UtUTLdpuQzvr6718y2CP0ouKt/1hVKD9QssT08XUvJEBQnnl2yVZAbIqT/DGnUH36L0BnQE/2ombPakwHscfFFAAAAQQCSfQy2cP8Oa0IR0u0whxqGmuuXY/3tCD8NaaSCYm31ly0QBdxFdf2WkC51DNVaf5/1ErHceMapFN9Z3j+/6lA7AAAAQQCFcMoSA32f240nFBmMv/nn/mL1uSdAXOxjUHViJc6M8ntZvW2ZuP2qTvfA3mh1AK5K69piX/4T72xxqTA2tmrfAAAAQFxX1JunFI+fpobdienVCZcjibwbpDPf1MVTbwQhAXHqVBL3XXgkysS/67X/aWnv/+SdBDaXa1SnDpphSWOkxAQ=");
//pub[0] 7
//pub[1] 1
//pub[2] 128
//pri[0] 128
//pri[1] 65
//pri[2] 65
//pri[3] 64
byte[] pubmod = null;
byte[] primod = null;
byte[] pubexp = null;
byte[] priexp = null;
pubexp = pub[0];
pubmod = pub[2];
priexp = pri[0];
primod = pri[2];
byte[] bstr = Encoding.ASCII.GetBytes("Test");
bstr = Encrypt(bstr, pubmod, pubexp);
bstr = Decrypt(bstr, pubexp, pubmod, null);
string str = Encoding.ASCII.GetString(bstr);
}

i do something like that:
public byte[] PublicDecryption(byte[] encryptedData)
{
var encData = new BigInteger(encryptedData);
BigInteger bnData = encData.modPow(_exponent, _modulus);
return bnData.getBytes();
}
public byte[] PrivateDecryption(byte[] encryptedData)
{
var encData = new BigInteger(encryptedData);
d = new BigInteger(rsaParams.D);
BigInteger bnData = encData.modPow(d, _modulus);
return bnData.getBytes();
}
where BigInteger is this:
http://www.codeproject.com/KB/cs/biginteger.aspx
because microsoft implementation is partial and buggy.
I've never had a problem with this.
Hope this help

Few month ago I have tried to implement scenario with private key encryption and public key decryption. I spent a week trying doing this with RSACryptoServiceProvider and.. nothing. They support only two use cases:
Public key encryption , private (full) key decryption.
Signing with private key, verifying with public.
And they have done everything to not allow you do something else with their API.
Please, check out msdn forums:
I have found many answers like that one msdn, including answers from support development team. All they said: that this is prohibit by design. So my suggestion is don't even try to do that with RSACryptoServiceProvider, better use another implementation.