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Throws error on Decrypting String c# code

Posted on 2016-11-16
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Last Modified: 2016-11-20
Hi experts ,

We are trying to encrypt and decrypt the password to store on database . we are successfully encrypt the password . but when we try to decrypt it shows error as
Length of the data to decrypt is invalid.
. Don't Understand why the error is occurred

 public static string DecryptString(string Message, string Passphrase)
        {
            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);

            // 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);
        }

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Any idea on this Experts
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Question by:karthik80c
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3 Comments
 
LVL 34

Expert Comment

by:sarabande
ID: 41889797
don't see any encrypting of 'Message' in your code.

Sara
0
 

Author Comment

by:karthik80c
ID: 41891177
Hi Sara ,

Which means you don't have the message to encrypt sara ?

and i don't know exactly . this line is responsible for encrypting

ICryptoTransform Decryptor = TDESAlgorithm.CreateDecryptor();
                Results = Decryptor.TransformFinalBlock(DataToDecrypt, 0, DataToDecrypt.Length);
            }

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LVL 34

Accepted Solution

by:
sarabande earned 500 total points
ID: 41891458
i don't know exactly . this line is responsible for encrypting

it can't as the 'Message' is not input. encrypting means that the message or a byte stream from message was converted to an encrypted byte-stream.

the code only does base64 translation on message text what is a 6-bit-to-8-bit transformation into a 64 character ASCII alphabet and not an encryption.

i think between step 3 and 4 (or between 4 and 5 if you want do base64 before) you have to add encoding ...

Sara
1

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