Develop Reference

C# Facing issue to encrypt and decrypt text by Base64

The text ZIRT which i encrypt by base64 this way
public static string encrypt(string ToEncrypt)
{
return Convert.ToBase64String(Encoding.ASCII.GetBytes(ToEncrypt));
}
after encrypt the text becomes V2tsU1ZB and when i try to decrypt using the below function
public static string decrypt(string cypherString)
{
//return Encoding.ASCII.GetString(Convert.FromBase64String(cypherString));
byte[] data = Convert.FromBase64String(cypherString);
string decodedString = Encoding.UTF8.GetString(data);
return decodedString;
}
then i am getting this text WklSVA but it suppose to be ZIRT
Please tell me what is wrong in my code ?
I am giving more code which fail to decrypt text
private void button1_Click(object sender, EventArgs e)
{
string strTxt = "ZIRT";
string ss = EnryptString(strTxt);
string ss1 = EnryptString(ss);
}
public string DecryptString(string encrString)
{
byte[] b;
string decrypted;
try
{
b = Convert.FromBase64String(encrString);
decrypted = System.Text.ASCIIEncoding.ASCII.GetString(b);
}
catch (FormatException fe)
{
decrypted = "";
}
return decrypted;
}
public string EnryptString(string strEncrypted)
{
byte[] b = System.Text.ASCIIEncoding.ASCII.GetBytes(strEncrypted);
string encrypted = Convert.ToBase64String(b);
return encrypted;
}

There is double encoding of the strings that explain the incorrect result. You are also using different text encodings when encrypting and decrypting. ASCII vs UTF8, this should be the same.
The following example provides the result I would expect:
byte[] b = System.Text.ASCIIEncoding.UTF8.GetBytes("test abc");
string base64Encoded = Convert.ToBase64String(b);
b = Convert.FromBase64String(base64Encoded);
Console.WriteLine( System.Text.ASCIIEncoding.UTF8.GetString(b));
// "test abc"
As mentioned in the comments, this is not encryption, but encoding.

Calculating HMACSHA256 using c# to match payment provider example

For a payment provider, I need to calculate a hash-based message authentication code, using HMAC-SHA256. That is causing me quite a bit of trouble.
The payment provider gives two examples of orrectly calculated authentication code in pseudo-code. All keys are in hex.
Method 1
key = 57617b5d2349434b34734345635073433835777e2d244c31715535255a366773755a4d70532a5879793238235f707c4f7865753f3f446e633a21575643303f66
message = "amount=100&currency=EUR"
MAC = HMAC-SHA256( hexDecode(key), message )
result = b436e3e86cb3800b3864aeecc8d06c126f005e7645803461717a8e4b2de3a905
Method 2
message = "amount=100&currency=EUR"
Ki = 61574d6b157f757d02457573556645750e0341481b127a07476303136c005145436c7b46651c6e4f4f040e1569464a794e534309097258550c17616075060950
Ko = 0b3d27017f151f17682f1f193f0c2f1f64692b227178106d2d096979066a3b2f2906112c0f760425256e647f032c2013243929636318323f667d0b0a1f6c633a
MAC = SHA256( hexDecode(Ko) + SHA256( hexDecode(Ki) + message ) )
result = b436e3e86cb3800b3864aeecc8d06c126f005e7645803461717a8e4b2de3a905
I tried to write the code to do this, after doing some research, but I keep coming up with different results.
private static void Main(string[] args)
{
var key = "57617b5d2349434b34734345635073433835777e2d244c31715535255a366773755a4d70532a5879793238235f707c4f7865753f3f446e633a21575643303f66";
var ki = "61574d6b157f757d02457573556645750e0341481b127a07476303136c005145436c7b46651c6e4f4f040e1569464a794e534309097258550c17616075060950";
var ko = "0b3d27017f151f17682f1f193f0c2f1f64692b227178106d2d096979066a3b2f2906112c0f760425256e647f032c2013243929636318323f667d0b0a1f6c633a";
var mm = "amount=100&currency=EUR";
var result1 = CalcHMACSHA256Hash(HexDecode(key), mm);
var result2 = CalcSha256Hash(string.Format("{0}{1}", HexDecode(ko), CalcSha256Hash(HexDecode(ki) + mm)));
Console.WriteLine("Expected: b436e3e86cb3800b3864aeecc8d06c126f005e7645803461717a8e4b2de3a905");
Console.WriteLine("Actual 1: " + result1);
Console.WriteLine("Actual 2: " + result2);
Console.WriteLine("------------------------------");
Console.ReadKey();
}
private static string HexDecode(string hex)
{
var sb = new StringBuilder();
for (int i = 0; i <= hex.Length - 2; i += 2)
{
sb.Append(Convert.ToString(Convert.ToChar(Int32.Parse(hex.Substring(i, 2), System.Globalization.NumberStyles.HexNumber))));
}
return sb.ToString();
}
private static string CalcHMACSHA256Hash(string plaintext, string salt)
{
string result = "";
var enc = Encoding.Default;
byte[]
baText2BeHashed = enc.GetBytes(plaintext),
baSalt = enc.GetBytes(salt);
System.Security.Cryptography.HMACSHA256 hasher = new HMACSHA256(baSalt);
byte[] baHashedText = hasher.ComputeHash(baText2BeHashed);
result = string.Join("", baHashedText.ToList().Select(b => b.ToString("x2")).ToArray());
return result;
}
public static string CalcSha256Hash(string input)
{
SHA256 sha256 = new SHA256Managed();
byte[] sha256Bytes = Encoding.Default.GetBytes(input);
byte[] cryString = sha256.ComputeHash(sha256Bytes);
string sha256Str = string.Empty;
for (int i = 0; i < cryString.Length; i++)
{
sha256Str += cryString[i].ToString("x2");
}
return sha256Str;
}
And this is the result I get:
Expected: b436e3e86cb3800b3864aeecc8d06c126f005e7645803461717a8e4b2de3a905
Actual 1: 421ce16f2036bb9f2a3770c16f01e9220f0232d45580584ca41768fd16c15fe6
Actual 2: 290f14398bf8c0959dfc963e2fd9c377534c6fec1983025d2ab192382f132b92
So with none of the two methods, I can get the result the provider example wants.
What am I missing here? Is it encoding? Is my hexDecode screwed up?
Test tool from payment provider: http://tech.dibs.dk/dibs_api/other_features/hmac_tool/
PHP sample code: http://tech.dibspayment.com/dibs_api/other_features/mac_calculation/

Edit: You likely are looking for a quick and simple way to do HMAC-SHA256 and not get into the finer details. The original question asks of those finer details which are explained further below.
I want to perform a HMAC-SHA256 on a byte[] message input
using System.Security.Cryptography;
...
private static byte[] HashHMAC(byte[] key, byte[] message)
{
var hash = new HMACSHA256(key);
return hash.ComputeHash(message);
}
I want to perform HMAC-SHA256 but I have a hex string input
In .NET 5 and above, use System.Convert.FromHexString like so, (thanks #proximab). If you're on pre-.NET 5, scroll to "Helper functions" which has alternative solutions.
using System;
using System.Security.Cryptography;
...
private static byte[] HashHMACHex(string keyHex, string messageHex)
{
var key = Convert.FromHexString(hexKey);
var message = Convert.FromHexString(messageHex);
var hash = new HMACSHA256(key);
return hash.ComputeHash(message);
}
I'm using a strange API service that sort of does HMAC, but it's something custom
Continue reading. You likely want to use "Method 2" below as a reference point and adjust it to however your service wants you to implement HMAC for message anti-tampering.
How HMAC-SHA256 Works (should you need to know how...)
Here we will compute an HMAC-SHA256 manually (this answers "Method 2" from the original question).
Assume outerKey, innerKey, and message are already byte arrays, we perform the following:
Notation: Assume A + B concatenates byte array A and B. You may
alternatively see A || B notation used in more academic settings.
HMAC = SHA256( outerKey + SHA256( innerKey + message ) )
. . `------------------´ . .
\ \ `innerData` / /
\ `------------------------´ /
\ `innerHash` /
`----------------------------------´
`data`
So the code can be broken down into these steps (using the above as a guide):
Create an empty buffer byte[] innerData the length of innerKey.Length + message.Length (again assuming byte arrays)
Copy the innerKey and the message into the byte[] innerData
Compute SHA256 of innerData and store it in byte[] innerHash
Create an empty buffer byte[] data the length of outerKey.Length + innerHash.Length
Copy the outerKey and innerHash (from step #3)
Compute the final hash of data and store it in byte[] result and return it.
To do the byte copying I'm using the Buffer.BlockCopy() function since it apparently faster than some other ways (source).
n.b. There is likely (read: most certainly) a better way to do this using the the new ReadOnlySpan<T> API.
We can translate those steps into the following:
using System;
using System.Security.Cryptography;
...
private static byte[] HashSHA(byte[] innerKey, byte[] outerKey, byte[] message)
{
var hash = new SHA256Managed();
// Compute the hash for the inner data first
byte[] innerData = new byte[innerKey.Length + message.Length];
Buffer.BlockCopy(innerKey, 0, innerData, 0, innerKey.Length);
Buffer.BlockCopy(message, 0, innerData, innerKey.Length, message.Length);
byte[] innerHash = hash.ComputeHash(innerData);
// Compute the entire hash
byte[] data = new byte[outerKey.Length + innerHash.Length];
Buffer.BlockCopy(outerKey, 0, data, 0, outerKey.Length);
Buffer.BlockCopy(innerHash, 0, data, outerKey.Length, innerHash.Length);
byte[] result = hash.ComputeHash(data);
return result;
}
Helper functions
string -> byte[]
You have plain ASCII or UTF8 text, but need it to be a byte[].
Use ASCIIEncoding or UTF8Encoding or whichever exotic encoding you're using.
private static byte[] StringEncode(string text)
{
var encoding = new System.Text.ASCIIEncoding();
return encoding.GetBytes(text);
}
byte[] -> hex string
You have a byte[], but you need it to be a hex string.
private static string HashEncode(byte[] hash)
{
return BitConverter.ToString(hash).Replace("-", "").ToLower();
}
hex string -> byte[]
You have a hex string, but you need it to be a byte[]`.
.NET 5 and above
private static byte[] HexDecode(string hex) =>
System.Convert.FromHexString(hex);
Before .NET 5 (thanks #bobince)
private static byte[] HexDecode(string hex)
{
var bytes = new byte[hex.Length / 2];
for (int i = 0; i < bytes.Length; i++)
{
bytes[i] = byte.Parse(hex.Substring(i * 2, 2), NumberStyles.HexNumber);
}
return bytes;
}
n.b. If you need a performance tuned version on .NET Framework 4.x, you can alternatively backport the .NET 5+ version (by replacing ReadOnlySpan<byte> with byte[]). It uses proper lookup tables and conscious about hot-code paths. You can reference the .NET 5 (MIT licensed) System.Convert code on Github.
For completeness, here are the final methods answering the question using both "Method 1" and "Method 2"
"Method 1" (using .NET libraries)
private static string HashHMACHex(string keyHex, string message)
{
byte[] hash = HashHMAC(HexDecode(keyHex), StringEncode(message));
return HashEncode(hash);
}
"Method 2" (manually computed)
private static string HashSHAHex(string innerKeyHex, string outerKeyHex, string message)
{
byte[] hash = HashSHA(HexDecode(innerKeyHex), HexDecode(outerKeyHex), StringEncode(message));
return HashEncode(hash);
}
We can perform a quick sanity check with a console app:
static void Main(string[] args)
{
string message = "amount=100&currency=EUR";
string expectedHex = "b436e3e86cb3800b3864aeecc8d06c126f005e7645803461717a8e4b2de3a905";
Console.WriteLine("Expected: " + expectedHex);
// Test out the HMAC hash method
string key = "57617b5d2349434b34734345635073433835777e2d244c31715535255a366773755a4d70532a5879793238235f707c4f7865753f3f446e633a21575643303f66";
string hashHMACHex = HashHMACHex(key, message);
Console.WriteLine("Method 1: " + hashHMACHex);
// Test out the SHA hash method
string innerKey = "61574d6b157f757d02457573556645750e0341481b127a07476303136c005145436c7b46651c6e4f4f040e1569464a794e534309097258550c17616075060950";
string outerKey = "0b3d27017f151f17682f1f193f0c2f1f64692b227178106d2d096979066a3b2f2906112c0f760425256e647f032c2013243929636318323f667d0b0a1f6c633a";
string hashSHAHex = HashSHAHex(innerKey, outerKey, message);
Console.WriteLine("Method 2: " + hashSHAHex);
}
You should have all the hashes line up correctly:
Expected: b436e3e86cb3800b3864aeecc8d06c126f005e7645803461717a8e4b2de3a905
Method 1: b436e3e86cb3800b3864aeecc8d06c126f005e7645803461717a8e4b2de3a905
Method 2: b436e3e86cb3800b3864aeecc8d06c126f005e7645803461717a8e4b2de3a905
The original code for this answer can be accessed at:
http://pastebin.com/xAAuZrJX

Here's a string extension method for getting a fairly standard HMAC SHA 256 token for a given string:
usage:
myMessageString.HmacSha256Digest(mySecret)
string extension method:
public static string HmacSha256Digest(this string message, string secret)
{
ASCIIEncoding encoding = new ASCIIEncoding();
byte[] keyBytes = encoding.GetBytes(secret);
byte[] messageBytes = encoding.GetBytes(message);
System.Security.Cryptography.HMACSHA256 cryptographer = new System.Security.Cryptography.HMACSHA256(keyBytes);
byte[] bytes = cryptographer.ComputeHash(messageBytes);
return BitConverter.ToString(bytes).Replace("-", "").ToLower();
}

You can use this method for HMACSHA256.
string key = "your key";
string message = "your message";
System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
byte[] keyByte = encoding.GetBytes(key);
HMACSHA256 hmacsha256 = new HMACSHA256(keyByte);
byte[] messageBytes = encoding.GetBytes(message);
byte[] hashmessage = hmacsha256.ComputeHash(messageBytes);
return ByteToString(hashmessage);
Here is the ByteToString method:
public static string ByteToString(byte[] buff)
{
string sbinary = "";
for (int i = 0; i < buff.Length; i++)
{
sbinary += buff[i].ToString("X2"); // hex format
}
return (sbinary);
}

A SHA hash is calculated on a sequence of bytes. Bytes are a profoundly different datatype to characters. You should not use character Strings to store binary data such as hashes.
sb.Append(Convert.ToString(Convert.ToChar(Int32.Parse(hex.Substring(i, 2)...
This creates a character string by reading each encoded byte and turning into a character of the same Unicode code point number. This is equivalent to decoding the bytes 0-255 using the ISO-8859-1 (Latin1) encoding, due to that encoding's property of matching the first 256 code points in Unicode.
var enc = Encoding.Default; [...]
baSalt = enc.GetBytes(salt);
byte[] sha256Bytes = Encoding.Default.GetBytes(input);
These both convert the characters back to bytes using the system default encoding. This encoding varies between installs, but it will never be ISO-8859-1 - even the similar Western European code page 1252 has different characters in the range 0x80-0x9F.
Consequently the byte array you are using doesn't contain the bytes implied by the example hex sequences. A cheap fix would be to use Encoding.GetEncoding("ISO-8859-1") instead of the default encoding, but really you should be using a bytes array to store data in the first place instead of a String, eg:
byte[] key= new byte[] { 0x57, 0x61, 0x7b, 0x5d, 0x23, 0x49, ... };
and pass that directly into ComputeHash.
If you must initialise data from a hex string, parse it directly into a byte array, eg:
private static byte[] HexDecode(string hex) {
var bytes= new byte[hex.Length/2];
for (int i= 0; i<bytes.Length; i++) {
bytes[i]= byte.Parse(hex.Substring(i*2, 2), NumberStyles.HexNumber);
}
return bytes;
}

I realize the question is answered, but I am posting this in case others need it. Here is a snippet of code created by the payment provider (DIBS):
/**
* calculateMac
* Calculates the MAC key from a Dictionary<string, string> and a secret key
* #param params_dict The Dictionary<string, string> object containing all keys and their values for MAC calculation
* #param K_hexEnc String containing the hex encoded secret key from DIBS Admin
* #return String containig the hex encoded MAC key calculated
**/
public static string calculateMac(Dictionary<string, string> paramsDict, string kHexEnc)
{
//Create the message for MAC calculation sorted by the key
var keys = paramsDict.Keys.ToList();
keys.Sort();
var msg = "";
foreach (var key in keys)
{
if (key != keys[0]) msg += "&";
msg += key + "=" + paramsDict[key];
}
//Decoding the secret Hex encoded key and getting the bytes for MAC calculation
var kBytes = new byte[kHexEnc.Length / 2];
for (var i = 0; i < kBytes.Length; i++)
{
kBytes[i] = byte.Parse(kHexEnc.Substring(i * 2, 2), NumberStyles.HexNumber);
}
//Getting bytes from message
var msgBytes = Encoding.Default.GetBytes(msg);
//Calculate MAC key
var hash = new HMACSHA256(kBytes);
var macBytes = hash.ComputeHash(msgBytes);
var mac = BitConverter.ToString(macBytes).Replace("-", "").ToLower();
return mac;
}
http://tech.dibspayment.com/DX/Hosted/HMAC

Thanks you saved my time.
request.Method = "GET";
string signature = "";
string strtime = DateTime.UtcNow.ToString("yyyy-MM-ddTHH\\:mm\\:ssZ");
string secret = "xxxx";
string message = "sellerid:email:" + strtime;
var encoding = new System.Text.ASCIIEncoding();
byte[] keyByte = encoding.GetBytes(secret);
byte[] messageBytes = encoding.GetBytes(message);
using (var hmacsha256 = new HMACSHA256(keyByte))
{
var hash = new HMACSHA256(keyByte);
byte[] signature1 = hash.ComputeHash(messageBytes);
signature = BitConverter.ToString(signature1).Replace("-", "").ToLower();
}
request.Headers.Add("authorization", "HMAC-SHA256" + " " +
"emailaddress=xxx#xx.com,timestamp=" + strtime + ",signature=" + signature);
HttpWebResponse response = request.GetResponse() as HttpWebResponse;

private static string GenerateSignature(string data, string signatureKey)
{
var keyByte = Encoding.UTF8.GetBytes(signatureKey);
using (var hmacsha256 = new HMACSHA256(keyByte))
{
hmacsha256.ComputeHash(Encoding.UTF8.GetBytes(data));
return hmacsha256.Hash.Aggregate("", (current, t) => current + t.ToString("X2")).ToLower();
}
}

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:
É?xø´ v´“Û·8êUŸí¥MïSÅJÖó5Cå7ã…ÄlÞ&þòG·¶ÝÙ3<ÍÖ¡«úüF¿¿ßìNµ>4¦Äu÷¼Â;£-w¤ƒûÊyL¹®½èíYö½’é(µJŒ~»»=3¼]F‡•=±Ùí]'鳫"øPç{Ù^yyéå–°ñ…5ðWF$zÉnÄ^_”Xë’ï%œ-5á
ÒÛ€jŠt`Â9œÇÞLU&¼~ç2îžúo/¢¶5,º*öOqÝ—‘.ó®šuf™å5G—õC®‰ÁéiÇúW®¦ÝÚ•Z±:„Q\p"p
ôÔiÛ!\D"ÉÂX3]ƒ°è€Œ«DQE‡kÝ#àö`gpöŽ÷nÛ={µÏßKQKüå(ö%¯¯Ü–9}¨¬°£7yo,«”ÜëCÍ/+…†ÕËî‘‹‰AÚmÇÙå©&©¡xÙkŒföX¯ÃX&×°S|kÜ6Ô°Üú\Ätóü-äUƆÈáÅ\ ’E8‚¤âÈ4Ž¾«ãΚ_Sï£y‰xJº•bm*jo›‰ÜW–[ô†ÆJÐà$½…9½šžˆ_ÙÜù/®öÁVhzŠ¥ú(ñ£²6ˆb6¢ëße¤oáIðZuK}ÆÙ]"T¼*åZêñß5K—½òQSåRN Çë'Å¡
ÕyiÈX •bØðIk¿WxwNàäx®‹?cv+X™¥E!gd4â¤nÔ‹¢½Ð”ªÊ­Q!‚.e8s
Gyª4¼ò,}Yœ‚¹”±E‡Jy}Sæ
ƒ¦ýK'Ð}~B¦E3!0°ú´A–5Þ³£9$–8äÏ©?
œ‡8GÂø
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

Unicode-to-string conversion in C#

How can I convert a Unicode value to its equivalent string?
For example, I have "రమెశ్", and I need a function that accepts this Unicode value and returns a string.
I was looking at the System.Text.Encoding.Convert() function, but that does not take in a Unicode value; it takes two encodings and a byte array.
I bascially have a byte array that I need to save in a string field and then come back later and convert the string first back to a byte array.
So I use ByteConverter.GetString(byteArray) to save the byte array to a string, but I can't get it back to a byte array.

Use .ToString();:
this.Text = ((char)0x00D7).ToString();

Try the following:
byte[] bytes = ...;
string convertedUtf8 = Encoding.UTF8.GetString(bytes);
string convertedUtf16 = Encoding.Unicode.GetString(bytes); // For UTF-16
The other way around is using `GetBytes():
byte[] bytesUtf8 = Encoding.UTF8.GetBytes(convertedUtf8);
byte[] bytesUtf16 = Encoding.Unicode.GetBytes(convertedUtf16);
In the Encoding class, there are more variants if you need them.

To convert a string to a Unicode string, do it like this: very simple... note the BytesToString function which avoids using any inbuilt conversion stuff. Fast, too.
private string BytesToString(byte[] Bytes)
{
MemoryStream MS = new MemoryStream(Bytes);
StreamReader SR = new StreamReader(MS);
string S = SR.ReadToEnd();
SR.Close();
return S;
}
private string ToUnicode(string S)
{
return BytesToString(new UnicodeEncoding().GetBytes(S));
}

UTF8Encoding Class
UTF8Encoding uni = new UTF8Encoding();
Console.WriteLine( uni.GetString(new byte[] { 1, 2 }));

There are different types of encoding. You can try some of them to see if your bytestream get converted correctly:
System.Text.ASCIIEncoding encodingASCII = new System.Text.ASCIIEncoding();
System.Text.UTF8Encoding encodingUTF8 = new System.Text.UTF8Encoding();
System.Text.UnicodeEncoding encodingUNICODE = new System.Text.UnicodeEncoding();
var ascii = string.Format("{0}: {1}", encodingASCII.ToString(), encodingASCII.GetString(textBytesASCII));
var utf = string.Format("{0}: {1}", encodingUTF8.ToString(), encodingUTF8.GetString(textBytesUTF8));
var unicode = string.Format("{0}: {1}", encodingUNICODE.ToString(), encodingUNICODE.GetString(textBytesCyrillic));
Have a look here as well: http://george2giga.com/2010/10/08/c-text-encoding-and-transcoding/.

var ascii = $"{new ASCIIEncoding().ToString()}: {((ASCIIEncoding)new ASCIIEncoding()).GetString(textBytesASCII)}";
var utf = $"{new UTF8Encoding().ToString()}: {((UTF8Encoding)new UTF8Encoding()).GetString(textBytesUTF8)}";
var unicode = $"{new UnicodeEncoding().ToString()}: {((UnicodeEncoding)new UnicodeEncoding()).GetString(textBytesCyrillic)}";

Wrote a cycle for converting unicode symbols in string to UTF8 letters:
string stringWithUnicodeSymbols = #"{""id"": 10440119, ""photo"": 10945418, ""first_name"": ""\u0415\u0432\u0433\u0435\u043d\u0438\u0439""}";
var splitted = Regex.Split(stringWithUnicodeSymbols, #"\\u([a-fA-F\d]{4})");
string outString = "";
foreach (var s in splitted)
{
try
{
if (s.Length == 4)
{
var decoded = ((char) Convert.ToUInt16(s, 16)).ToString();
outString += decoded;
}
else
{
outString += s;
}
}
catch (Exception e)
{
outString += s;
}
}

.NET Equivalent of MD5.hex() in Javascript

I'm trying to connect to a website I made with auth that uses MD5.hex(password) to encrypt the password before sending it to the PHP. How could I achieve the same encryption in C#?
EDIT1:
Javascript (YUI Library):
pw = MD5.hex(pw);
this.chap.value = MD5.hex(pw + this.token.value);
C#.NET
string pw = getMD5(getHex(getMD5(getHex(my_password)) + my_token));
Utility:
public string getMD5(string input)
{
// Create a new instance of the MD5CryptoServiceProvider object.
MD5 md5Hasher = MD5.Create();
// Convert the input string to a byte array and compute the hash.
byte[] data = md5Hasher.ComputeHash(Encoding.Default.GetBytes(input));
// Create a new Stringbuilder to collect the bytes
// and create a string.
StringBuilder sBuilder = new StringBuilder();
// Loop through each byte of the hashed data
// and format each one as a hexadecimal string.
for (int i = 0; i < data.Length; i++)
{
sBuilder.Append(data[i].ToString("x2"));
}
// Return the hexadecimal string.
return sBuilder.ToString();
}
public string getHex(string asciiString)
{
string hex = "";
foreach (char c in asciiString)
{
int tmp = c;
hex += String.Format("{0:x2}", (uint)System.Convert.ToUInt32(tmp.ToString()));
}
return hex;
}

Using .NET's MD5 Class in the System.Security.Cryptography namespace.
The link above contains a short code example; you might also want to check out Jeff Attwood's CodeProject article .NET Encryption Simplified.