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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

Get a C# byte array equal to a php hex string

So I have this piece of php code that I'm not allowed to modify for now, mainly because it's old and works properly.
Warning! Very bad code overal. the IV is not being randomized neither stored with the output. I'm not asking this because I want to,
I'm asking because I need to. I'm also planning on refactoring when I get this working and completing my C# code with actually reliable cyphering code.
function encrypt($string)
{
$output = false;
$encrypt_method = "AES-256-CBC";
$param1 = 'ASasd564D564aAS64ads564dsfg54er8G74s54hjds346gf445gkG7';
$param2 = '654dsfg54er8ASG74sdfg54hjdas346gf34kjdDJF56hfs2345gkFG';
$ky = hash('sha256', $param1); // hash
$iv = substr(hash('sha256', $param2), 0, 16);
$output = openssl_encrypt($string, $encrypt_method, $ky, 0, $iv);
$output = base64_encode($output);
return $output;
}
I want to do the same in C# because I'm getting an entity with all its fields encrypted with that code.
I want to be able to encrypt that data so I can query my entity list whithout having to decrypt all the entities. And I want to decrypt some properties of the filtered entities so they can actually be useful.
Now, for that matter I created a CryptoHelper that will do this, except it doesn't.
I try to calculate the Key and IV in the constructor:
public readonly byte[] Key;
public readonly byte[] IV;
public CryptoHelper()
{
Key = GetByteArraySha256Hash("ASasd564D564aAS64ads564dsfg54er8G74s54hjds346gf445gkG7", false);
IV = GetByteArraySha256Hash("654dsfg54er8ASG74sdfg54hjdas346gf34kjdDJF56hfs2345gkFG", true);
}
private byte[] GetByteArraySha256Hash(string source, bool salt)
{
byte[] result;
try
{
using (SHA256 sha256Hash = SHA256.Create())
{
result = sha256Hash.ComputeHash(Encoding.UTF8.GetBytes(source));
}
}
catch (Exception)
{
throw;
}
if (salt)
{
return result.Take(16).ToArray();
}
return result;
}
And then use a Encrypt and Decrypt methods that are working pretty well when I test them with a test string. The only problem is that the string have some padding at the end, but it's kind of a minor problem considering that any string encrypted with the php method results in gibberish.
private string Encrypt(string source)
{
try
{
string result = "";
using (var aes = new AesManaged { Key = Key, IV = IV, Mode = CipherMode.CBC, Padding = PaddingMode.Zeros })
{
byte[] sourceByteArray = Encoding.UTF8.GetBytes(source);
using (var encryptor = aes.CreateEncryptor(aes.Key, aes.IV))
{
byte[] encriptedSource = encryptor.TransformFinalBlock(sourceByteArray, 0, sourceByteArray.Length);
result = Convert.ToBase64String(encriptedSource);
result = Convert.ToBase64String(Encoding.UTF8.GetBytes(result));
}
}
return result;
}
catch (Exception ex)
{
throw;
}
}
private string Decrypt(string source)
{
try
{
string result = "";
//Double Base64 conversion, as it's done in the php code.
byte[] sourceByte = Convert.FromBase64String(source);
byte[] sourceFreeOfBase64 = Convert.FromBase64String(Encoding.UTF8.GetString(sourceByte));
byte[] resultByte;
int decryptedByteCount = 0;
using (var aes = new AesManaged { Key = Key, IV = IV, Mode = CipherMode.CBC, Padding = PaddingMode.Zeros })
{
using (ICryptoTransform AESDecrypt = aes.CreateDecryptor(aes.Key, aes.IV))
{
using (MemoryStream memoryStream = new MemoryStream(sourceFreeOfBase64))
{
using (CryptoStream cs = new CryptoStream(memoryStream, AESDecrypt, CryptoStreamMode.Read))
{
resultByte = new byte[sourceFreeOfBase64.Length];
decryptedByteCount = cs.Read(resultByte, 0, resultByte.Length);
}
}
}
//This returns the encoded string with a set of "\0" at the end.
result = Encoding.UTF8.GetString(resultByte);
result = result.Replace("\0", "");
}
return result;
}
catch (Exception ex)
{
throw;
}
}
I'm pretty sure that the main problem here lies in the php line $iv = substr(hash('sha256', $param2), 0, 16);. I checked the results of both hash functions in php and C# and are exactly the same.
From what I've been reading php treats strings as byte arrays (correct me if I'm wrong) so a 16 char string should be enough to get a 16 byte array and a 128 block. But in C#, when I get the 16 byte array and convert it to a string I get a 32 char string that is the same as if I did $iv = substr(hash('sha256', $param2), 0, 32);.
So my question is, how do I get the same byte array result in C# that I get in this line $iv = substr(hash('sha256', $param2), 0, 16); of php? Is this even possible?

The hash function will return the same number of bytes whatever the input, so I suspect it is a difference in how you convert the resulting byte[] back to a string in C# compared to the PHP implementation.
The PHP docs say that the hash function output the result in lower case hexits. This is absolutely not the same as the UTF8 encoding that you are returning.
There isn't a built in framework way to do this, but check out this SO question for several different methods.
Also worth noting is that you do not specify the Padding value in your C# code. AES-CBC is a block cipher and will need to use some padding scheme. You may well get a padding exception. I think that it will need Zero padding (docs)
aes.Padding = PaddingMode.Zeros
but I'm not 100%

Well, I managed to solve this in a not so bad manner.
Following #ste-fu advice I tried to get rid of every piece of encoding that I could find.
But I still wasn't anywhere close to getting the Key and IV right. So I did some testing with php. I made a var_dump of the IV and got a neat 16 length array with bytes shown as integers.
var_dump result array starts allways in [1]. Be advised.
$iv = substr(hash('sha256', $param2), 0, 16);
$byte_array = unpack('C*', $iv);
var_dump($byte_array);
That peaked my interest, thinking that if I had the hex string right I should be able to convert each char in the string to it's equivalent byte. Lo and behold, I made this function in C#:
private byte[] StringToByteArray(string hex)
{
IList<byte> resultList = new List<byte>();
foreach (char c in hex)
{
resultList.Add(Convert.ToByte(c));
}
return resultList.ToArray();
}
And this worked very well for the IV. Now I just had to do the same thing for the key. And so I did, just to find that I had a 64 length byte array. That's weird, but ok. More testing in php.
Since it does make sense that the php Key behaves the same as the IV I didn't get how the openssl encryption functions allowed a 64 length Key. So I tryed to encrypt and decrypt the same data with a Key made from the first 32 chars. $ky = substr(hash('sha256', $param1), 0, 32);
And it gave me the same result as with the full Key. So, my educated guess is that openssl just takes the bytes necesary for the encoding to work. In fact it will take anything since I tested with substrings of 1, 16, 20, 32, 33 and 50 length. If the length of the string is bigger than 32 the function itself will cut it.
Anyway, i just had to get the first 32 chars of the Key hex and use my new function to convert them into a byte array and I got my Key.
So, the main C# code right now looks like this:
public CryptoHelper(string keyFilePath, string ivFilePath)
{
//Reading bytes from txt file encoded in UTF8.
byte[] key = File.ReadAllBytes(keyFilePath);
byte[] iv = File.ReadAllBytes(ivFilePath);
IV = StringToByteArray(GetStringHexSha256Hash(iv).Substring(0, 16));
Key = StringToByteArray(GetStringHexSha256Hash(key).Substring(0, 32));
//Tests
var st = Encrypt("abcdefg");
var en = Decrypt(st);
}
//Convert each char into a byte
private byte[] StringToByteArray(string hex)
{
IList<byte> resultList = new List<byte>();
foreach (char c in hex)
{
resultList.Add(Convert.ToByte(c));
}
return resultList.ToArray();
}
private string GetStringHexSha256Hash(byte[] source)
{
string result = "";
try
{
using (SHA256 sha256Hash = SHA256.Create("SHA256"))
{
//Get rid of Encoding!
byte[] hashedBytes = sha256Hash.ComputeHash(source);
for (int i = 0; i < hashedBytes.Length; i++)
{
result = string.Format("{0}{1}",
result,
hashedBytes[i].ToString("x2"));
}
}
}
catch (Exception)
{
throw;
}
return result;
}
private string Encrypt(string source)
{
try
{
string result = "";
using (var aes = new AesManaged { Key = Key, IV = IV, Mode = CipherMode.CBC, Padding = PaddingMode.PKCS7 })
{
byte[] sourceByteArray = Encoding.UTF8.GetBytes(source);
using (var encryptor = aes.CreateEncryptor(aes.Key, aes.IV))
{
byte[] encriptedSource = encryptor.TransformFinalBlock(sourceByteArray, 0, sourceByteArray.Length);
result = Convert.ToBase64String(encriptedSource);
//Nothing to see here, move along.
result = Convert.ToBase64String(Encoding.UTF8.GetBytes(result));
}
}
return result;
}
catch (Exception ex)
{
throw;
}
}
private string Decrypt(string source)
{
try
{
string result = "";
byte[] sourceByte = Convert.FromBase64String(source);
byte[] sourceFreeOfBase64 = Convert.FromBase64String(Encoding.UTF8.GetString(sourceByte));
byte[] resultByte;
int decryptedByteCount = 0;
using (var aes = new AesManaged { Key = Key, IV = IV, Mode = CipherMode.CBC, Padding = PaddingMode.PKCS7 })
{
using (ICryptoTransform AESDecrypt = aes.CreateDecryptor(aes.Key, aes.IV))
{
using (MemoryStream memoryStream = new MemoryStream(sourceFreeOfBase64))
{
using (CryptoStream cs = new CryptoStream(memoryStream, AESDecrypt, CryptoStreamMode.Read))
{
resultByte = new byte[sourceFreeOfBase64.Length];
//Now that everything works as expected I actually get the number of bytes decrypted!
decryptedByteCount = cs.Read(resultByte, 0, resultByte.Length);
}
}
}
//Nothing to see here, move along.
result = Encoding.UTF8.GetString(resultByte);
//Use that byte count to get the actual data and discard the padding.
result = result.Substring(0, decryptedByteCount);
}
return result;
}
catch (Exception ex)
{
throw;
}
}
I still need to clean all the code from my class from all the testing I did, but this is all that's needed to make it work.
I hope this helps anybody with the same problem that I faced.
Cheers.

AES encryption in C Sharp and decryption in Android using PBKDF2WithHmacSHA1

I am using Android and I am trying to decrypt a message encrypted in a C Sharp Server.
Below is the code for the C# Cryptor, that uses 256 bit long Keys, 128 bit long IV, 5000 Iterations. It uses Rfc2898DeriveBytes Class, so that is the same as PBKDF2WithHmacSHA1 in Android.
The decrypt function of the C# Cryptor takes as its IV the (reversed) first 128 bits of the 256 bit long key.
namespace CompanyName.Framework.Encryption
{
internal class SymmetricCryptor : ISymmetricCryptor
{
internal static int KeyLengthInBytes = 32;
internal int Iterations = 5000;
#region Private Fields
// RijndaelManaged aes; old version
AesManaged aes;
int IVLength = KeyLengthInBytes >> 1;
#endregion Private Fields
#region Internal Constructors
internal SymmetricCryptor( )
{
aes = new AesManaged
{
Mode = CipherMode.CBC,
KeySize= KeyLengthInBytes<<3,
Padding = PaddingMode.PKCS7,
};
//aes.KeySize = KeyLengthInBytes << 3;
//aes.Padding = PaddingMode.Zeros; //PKCS7 can not be used with stream
}
#endregion Internal Constructors
#region Public Methods
public byte[] Decrypt(byte[] cryptedData, string password, IVMode ivmode)
{
using (MemoryStream ms = new MemoryStream(cryptedData))
{
using (MemoryStream data = new MemoryStream())
{
Decrypt(ms, data, password,ivmode);
return data.ToArray();
}
}
}
public void Encrypt(Stream data, Stream trgStream, string password, IVMode ivmode)
{
try
{
var key = GetKey(password);
var iv = (ivmode == IVMode.Auto)
?key.GetBytes(IVLength).Reverse().ToArray()
: new byte[IVLength];
var dc = aes.CreateEncryptor(key.GetBytes(KeyLengthInBytes), iv);
using (CryptoStream cryptor = new CryptoStream(trgStream, dc, CryptoStreamMode.Write))
{
data.CopyTo(cryptor);
cryptor.FlushFinalBlock();
cryptor.Close();
}
}
catch (Exception)
{
throw new InvalidOperationException("Invalid password.");
}
}
public void Decrypt(Stream cryptedData, Stream trgStream, string password, IVMode ivmode)
{
try
{
var key= GetKey(password);
var iv = (ivmode == IVMode.Auto)
? key.GetBytes(IVLength).Reverse().ToArray()
: new byte[IVLength];
var dc = aes.CreateDecryptor(key.GetBytes(KeyLengthInBytes),iv);
using (CryptoStream cryptor = new CryptoStream(cryptedData, dc, CryptoStreamMode.Read))
{
cryptor.CopyTo(trgStream);
cryptor.Close();
}
}
catch (Exception)
{
throw new InvalidOperationException("Invalid password.");
}
}
public byte[] Encrypt(byte[] data, string password, IVMode ivmode)
{
using (MemoryStream ms = new MemoryStream(data))
{
using (MemoryStream cData = new MemoryStream())
{
Encrypt(ms, cData, password,ivmode);
return cData.ToArray();
}
}
}
#endregion Public Methods
#region Private Methods
private Rfc2898DeriveBytes GetKey(string password)
{
try
{
var iv =
CompanyName.Framework.Cryptography.Digest.SHA1.Compute(password);
return new Rfc2898DeriveBytes(password, iv, Iterations);
}
catch (Exception)
{
throw;
}
}
#endregion Private Methods
}
}
My Android Cryptor, which tries to decrypt a message encrypted by the above C Sharp Cryptor looks like this, I tried to copy the Decrypt method of the C Sharp Cryptor:
public class Cryptor {
private static final String TRANSFORMATION = "AES/CBC/PKCS7Padding";
private static final String AES = "AES";
private static final String RANDOM_ALGO = "SHA1PRNG";
private static final int KEY_LENGTH_IN_BITS = 256;
private static final int IV_LENGTH = 16;
private static final int PBE_ITERATION_COUNT = 5000;
private static final int PBE_SALT_LENGTH_INT_BITS = 128;
private static final String PBE_ALGO = "PBKDF2WithHmacSHA1";
public static byte[] generateKeyFromPassword(String password, int Size) throws GeneralSecurityException {
byte[] salt = generateSalt();
KeySpec keySpec = new PBEKeySpec(password.toCharArray(), salt, PBE_ITERATION_COUNT, Size);
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(PBE_ALGO);
byte[] data = keyFactory.generateSecret(keySpec).getEncoded();
return data;
}
private static byte[] generateSalt() throws GeneralSecurityException {
return randomBytes(PBE_SALT_LENGTH_INT_BITS);
}
private static byte[] randomBytes(int length) throws GeneralSecurityException {
SecureRandom random = SecureRandom.getInstance(RANDOM_ALGO);
byte[] b = new byte[length];
random.nextBytes(b);
return b;
}
public static byte[] decrypt(byte[] cipherText, String password) throws GeneralSecurityException {
byte[] keyBytes = generateKeyFromPassword(password, 256);
byte[] ivBytes = generateKeyFromPassword(password, 128);
Cipher cipher = Cipher.getInstance(TRANSFORMATION);
ivBytes = reverse(ivBytes);
SecretKeySpec secretKey = new SecretKeySpec(keyBytes, AES);
IvParameterSpec ivSpec = new IvParameterSpec(ivBytes);
cipher.init(Cipher.DECRYPT_MODE, secretKey, ivSpec);
byte[] decrypted = cipher.doFinal(cipherText);
return decrypted;
}
public static byte[] reverse(byte[] array) {
if (array == null) {
return null;
}
int i = 0;
int j = array.length - 1;
byte tmp;
while (j > i) {
tmp = array[j];
array[j] = array[i];
array[i] = tmp;
j--;
i++;
}
return array;
}
But it is not working, When do final is called I get a
javax.crypto.BadPaddingException: error:1e06b065:Cipher functions:EVP_DecryptFinal_ex:BAD_DECRYPT
Exception. I am not sure what I am doing wrong, because my Decrypt Method in Android is doing the exact same thing as the Decrypt Method in C Sharp: First I generate a Key from the password, which is shared by the Csharp Server and me. Then I generate a random 128 bit IV, reversing it is not necessary, but C Sharp implementation reverses it, so I do it as well. Can anyone tell me what I am doing wrong? Here is the context where I use the Cryptor:
//open the client channel, read and return the response as byte[]
Channel clientChannel = new Channel(serverAddress);
byte[] result = clientChannel.execute(serviceID.toString(), data);
//result[] is encrypted data. firstTen is the shared Password
byte[] decrypted = Cryptor.decrypt(result, firstTen);
Server returns the result as Base64 encrypted, before passing it for decryption I get the result[] array through:
It comes as a Base64 String. I get the result[] array through:
Base64.decode(result, Base64.NO_WRAP);

You need to generate random salt and IV on Server side and sent it with ciphreText to Android side. Android need to use exactly the same salt and IV to derive key for decryption that that was used to derive encryption key on Server side.

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 ;
}

Is there anything wrong with this RC4 encryption code in C#

I am trying to listen to the Foxycart XML Datafeed in C# and running into an issue which boils down to encryption.
In short, they send over their data as encoded and encrypted XML using RC4 encryption.
To test, they have some (user submitted) sample code to test this with C#. I tried using this sample RC4 decryption code provided by one of the users but it doesn't seem to work and their support staff thinks its down with the C# RC4 algorithm. Since they are not C# experts, i figured i would ask here. Here is the post on the FoxyCart forum
Anyway, here is the code that (tries to) simulate the response by encrypting an XML file and posting it to a URL (NOTE that DataFeedKey is a string that i have stored as a member variable):
public ActionResult TestDataFeed()
{
string transactionData = (new StreamReader(#"D:\SampleFeed.xml")).ReadToEnd();
string encryptedTransactionData = RC4.Encrypt(DataFeedKey, transactionData, false);
string encodedTransactionData = HttpUtility.UrlEncode(encryptedTransactionData, Encoding.GetEncoding(1252));
string postData = "FoxyData=" + encodedTransactionData;
var req = (HttpWebRequest)WebRequest.Create("http://localhost:3396/FoxyCart/RecieveDataFeed");
req.Method = "POST";
req.ContentType = "application/x-www-form-urlencoded";
var sw = new StreamWriter(req.GetRequestStream(), Encoding.ASCII);
sw.Write(postData);
sw.Close();
HttpWebResponse resp = null;
try
{
resp = (HttpWebResponse)req.GetResponse();
string r = new StreamReader(resp.GetResponseStream()).ReadToEnd();
}
catch (WebException ex)
{
string err = new StreamReader(ex.Response.GetResponseStream()).ReadToEnd();
}
return null;
}
and here is the callback method that receives the response.
[ValidateInput(false)]
public ActionResult RecieveDataFeed(FormCollection collection)
{
string unencodedFeed = HttpUtility.UrlDecode(collection["FoxyData"], Encoding.GetEncoding(1252));
string transaction = RC4.Decrypt(DataFeedKey, unencodedFeed, false);
return Content("foxy");
}
Instead of posting the whole RC4 class inline in this question, here is a link to the code of this RC4 class.
As i posted in the above link at the top of the question, the issue is when i check the variable transaction inside the
RecieveDataFeed()
method, i should have the regular XML back but instead i see this:
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The code looks right:
Encrypt
Encode
Decode
Decrypt
but it doesn't seem to be working. Any suggestions on what might be wrong above?

I am a bit surprised by the code in the CR4 class. I can't see how it would work reliably.
The code uses windows-1252 encoding to encode characters into bytes, then it encrypts the bytes and tries to decode the bytes into characters. That won't work reliably, as you can only decode bytes that comes from encoding characters.
The method takes a string and returns a string, but it should take a byte array and return a byte array, similar to how all the encryption classes in the framework does it.
Here is a version that works like that:
public class RC4 {
public static byte[] Encrypt(byte[] pwd, byte[] data) {
int a, i, j, k, tmp;
int[] key, box;
byte[] cipher;
key = new int[256];
box = new int[256];
cipher = new byte[data.Length];
for (i = 0; i < 256; i++) {
key[i] = pwd[i % pwd.Length];
box[i] = i;
}
for (j = i = 0; i < 256; i++) {
j = (j + box[i] + key[i]) % 256;
tmp = box[i];
box[i] = box[j];
box[j] = tmp;
}
for (a = j = i = 0; i < data.Length; i++) {
a++;
a %= 256;
j += box[a];
j %= 256;
tmp = box[a];
box[a] = box[j];
box[j] = tmp;
k = box[((box[a] + box[j]) % 256)];
cipher[i] = (byte)(data[i] ^ k);
}
return cipher;
}
public static byte[] Decrypt(byte[] pwd, byte[] data) {
return Encrypt(pwd, data);
}
}
Example:
string data = "This is a test.";
byte[] key = { 1, 2, 3, 4, 5 };
// encrypt
byte[] enc = RC4.Encrypt(key, Encoding.UTF8.GetBytes(data));
// turn into base64 for convenient transport as form data
string base64 = Convert.ToBase64String(enc);
Console.WriteLine(base64);
// turn back into byte array
byte[] code = Convert.FromBase64String(base64);
// decrypt
string dec = Encoding.UTF8.GetString(RC4.Decrypt(key, code));
Console.WriteLine(dec);
Output:
5lEKdtBUswet4yYveWU2
This is a test.

Although this is more shooting in the dark... I am rather certain that the class implementing RC4 looks like it is assuming everyting is either ASCII or CodePage 1252 - both is wrong because I assume that the XML supplied is UTF-8 and .NET string represantion in memory is UTF16...
If my assumption is right the data is already scrambled when you get it back from encryption...
EDIT - some links to working RC4 code in C#:
http://tofuculture.com/Blog/post/RC4-Encryption-in-C.aspx
http://dotnet-snippets.com/dns/rc4-encryption-SID577.aspx
http://www.codeproject.com/KB/recipes/rc4csharp.aspx
http://icodesnip.com/snippet/csharp/rc4-encryption-code-snippets