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byte[] cryptKey = derive(secretKey, "ENCRYPTION");
byte[] signKey = derive(secretKey, "SIGNATURE");
static byte[] derive(string secret, string prefix)
{
using(HashAlgorithm hashAlg = HashAlgorithm.Create("SHA256"))
{
const int keyLength = 16;
byte[] data = Encoding.Default.GetBytes(prefix+secret);
byte[] hashOutput = hashAlg.ComputeHash(data);
byte[] byteKey = new byte[keyLength];
Array.Copy(hashOutput, byteKey, keyLength);
return byteKey;
}
}
const int ivLength = 16;
token = HttpUtility.UrlDecode(token);
byte[] ivAndEncryptedValue = Convert.FromBase64String(token);
aesAlg = new RijndaelManaged();
aesAlg.KeySize = 128;
aesAlg.Key = cryptKey;
aesAlg.Padding = PaddingMode.PKCS7;
memStream = new MemoryStream(ivAndEncryptedValue);
byte[] iv = new byte[ivLength];
memStream.Read(iv, 0, ivLength);
aesAlg.IV = iv;
cStream = new CryptoStream(memStream, aesAlg.CreateDecryptor(), CryptoStreamMode.Read);
sReader = new StreamReader(cStream, Encoding.ASCII);
decodedValue = sReader.ReadToEnd(); |
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