Encryption and decryption error

Question

I have a rather simple code for encryption and decryption. However, when I encrypt then decrypt, the output is not what I originally input.

This is the encryption:

static byte[] Encrypt(SymmetricAlgorithm aesAlg, string plainText)
    {
        ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

        using (MemoryStream msEncrypt = new MemoryStream())
        {
            using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
            {
                using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                {
                    swEncrypt.Write(plainText);
                }
                return msEncrypt.ToArray();
            }
        }
    }

Decryption:

static string Decrypt(SymmetricAlgorithm aesAlg, byte[] cipherText)
    {
        ICryptoTransform decryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

        using (MemoryStream msDecrypt = new MemoryStream(cipherText))
        {
            using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
            {
                using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                {
                    return srDecrypt.ReadToEnd();
                }
            }
        }
    }

Main:

public static void Main()
    {
        string original = "My secret data!";

        using (SymmetricAlgorithm symmetricAlgorithm = new AesManaged())
        {
            byte[] encrypted = Encrypt(symmetricAlgorithm, original);
            string roundtrip = Decrypt(symmetricAlgorithm, encrypted);

            Console.WriteLine("Original: {0}", original);
            Console.WriteLine("RoundTrip: {0}", roundtrip);
        }
    }

Ouput should be:

Original: My secret data!
RoundTrip: My secret data!

However, it comes out as:

Original: My secret data!
RoundTrip: ">�����6dB&JD䮦�L�ܹ�SKo\v*.�"

or something funny like that.

I couldn't find anything helpful on the internet. Any suggestions are greatly appreciated.

use aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV); for decryption — Sarvesh Mishra, Dec 09 '14 at 17:34
possible duplicate of [Encrypting & Decrypting a String in C#](http://stackoverflow.com/questions/10168240/encrypting-decrypting-a-string-in-c-sharp) — John Alexiou, Dec 15 '14 at 18:31

score 1 · Accepted Answer · answered Dec 09 '14 at 17:31

1

The problem is that in your Decrypt method you create another encryptor, not a Decryptor!

If you change the line

aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

to

aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

Then you will get the decypted text.

answered Dec 09 '14 at 17:31

Joey Ciechanowicz

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score -1 · Answer 2 · answered Dec 09 '14 at 17:36

Decryption code

static string Decrypt(SymmetricAlgorithm aesAlg, byte[] cipherText)
{
    ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

    using (MemoryStream msDecrypt = new MemoryStream(cipherText))
    {
        using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
        {
            using (StreamReader srDecrypt = new StreamReader(csDecrypt))
            {
                return srDecrypt.ReadToEnd();
            }
        }
    }
}

So, what is it you're saying besides a code dump? – Artjom B. Dec 09 '14 at 17:42 — Artjom B., Dec 09 '14 at 17:42

Encryption and decryption error

2 Answers2