Décryptage MD5 : Length of the data to decrypt is invalid.

Salut,

J'essaie de décrypter une string avec MD5. Ma méthode string Md5Encrypt(string Message) semble marcher uniquement quand la taille de Message est inférieure à 8 chars. Au-dessus de 7 chars la méthode lance l'exception suivante sur le code

Code:

Results = Decryptor.TransformFinalBlock(DataToDecrypt, 0, DataToDecrypt.Length);

Error message

Citation:

Length of the data to decrypt is invalid.

StackTrace :

Citation:

at System.Security.Cryptography.CryptoAPITransform.TransformFinalBlock(Byte[] inputBuffer, Int32 inputOffset, Int32 inputCount)
at Gpeto.Functions.Md5Decrypt(String

Voici la méthode (extraite du site suivant )
Code :

Code:

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public static string Md5Decrypt(string Message)
        {
            try
            {
                if (Message == null)
                    return null;
                string Passphrase = "KeyWord";
                byte[] Results;
                System.Text.UTF8Encoding UTF8 = new System.Text.UTF8Encoding();
 
                // Step 1. We hash the passphrase using MD5
                // We use the MD5 hash generator as the result is a 128 bit byte array
                // which is a valid length for the TripleDES encoder we use below
 
                MD5CryptoServiceProvider HashProvider = new MD5CryptoServiceProvider();
                byte[] TDESKey = HashProvider.ComputeHash(UTF8.GetBytes(Passphrase));
 
                // Step 2. Create a new TripleDESCryptoServiceProvider object
                TripleDESCryptoServiceProvider TDESAlgorithm = new TripleDESCryptoServiceProvider();
 
                // Step 3. Setup the decoder
                TDESAlgorithm.Key = TDESKey;
                TDESAlgorithm.Mode = CipherMode.ECB;
                TDESAlgorithm.Padding = PaddingMode.PKCS7;
 
                // Step 4. Convert the input string to a byte[]
                byte[] DataToDecrypt = Convert.FromBase64String(Message.Replace(' ','+'));
 
                // Step 5. Attempt to decrypt the string
                try
                {
                    ICryptoTransform Decryptor = TDESAlgorithm.CreateDecryptor();
                    Results = Decryptor.TransformFinalBlock(DataToDecrypt, 0, DataToDecrypt.Length);
                }
                finally
                {
                    // Clear the TripleDes and Hashprovider services of any sensitive information
                    TDESAlgorithm.Clear();
                    HashProvider.Clear();
                }
 
                // Step 6. Return the decrypted string in UTF8 format
                return UTF8.GetString(Results);
 
            }
            catch (Exception v_oEx)
            {
                throw new Exception("Unable to decrypt the word");
            }
        }