Question

I’m using this function to Encrypt/Decrypt data using AES because it looked simple and clean (googl’ed code)

public static string Encrypt(string toEncrypt)
    {
        byte[] keyArray = UTF8Encoding.UTF8.GetBytes("3a8114db34d5623d4fd1ee0fb0ga7a73"); // 256-AES key
        byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(toEncrypt);
        RijndaelManaged rDel = new RijndaelManaged();
        rDel.Key = keyArray;
        rDel.Mode = CipherMode.CBC;
        rDel.Padding = PaddingMode.PKCS7; // better lang support
        ICryptoTransform cTransform = rDel.CreateEncryptor();
        byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
        return Convert.ToBase64String(resultArray, 0, resultArray.Length);
    }
    public static string Decrypt(string toDecrypt)
    {
        byte[] keyArray = UTF8Encoding.UTF8.GetBytes("3a8114db34d5623d4fd1ee0fb0ga7a73"); // AES-256 key
        byte[] toEncryptArray = Convert.FromBase64String(toDecrypt);
        RijndaelManaged rDel = new RijndaelManaged();
        rDel.Key = keyArray;
        rDel.Mode = CipherMode.CBC;
        rDel.Padding = PaddingMode.PKCS7; // better lang support
        ICryptoTransform cTransform = rDel.CreateDecryptor();
        byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
        return UTF8Encoding.UTF8.GetString(resultArray);
    }

I’m trying to encrypt the data “test garbage” and thats what i receive back:

YfhyS3GE/liPCaXR0cMHfQ==

However, I tried the same key/phrase on a lot of online-aes encrypt/decrypt and all of them are returning

U2FsdGVkX184u0/vPgA/B0rxofp5Iuqm7hfn4+QZAhg=

Can anyone actually tell me whats wrong?

Answer 1

“3a8114db34d5623d4fd1ee0fb0ga7a73” is hex encoded 128 bit key not a utf8 encoded 256 bit key.

That said simple and clean doesn’t necessarily mean correct. For example, the code your using does use a random IV, but doesn’t include it in the wire format, you’ll never be able to decrypt what you encrypt.

I have a cut and paste style simple code sample that I try to keep up to date and reviewed that uses authenticated encryption using AES:

Modern Examples of Symmetric Authenticated Encryption of a string. C#