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369

answers:

2

Every time I run this and encrypt, the output is variable, and when I attempt to decrypt I get "Padding is invalid and cannot be removed." Been fighting with this for a day or two now and I am at a loss.

    private static string strIV = "abcdefghijklmnmo"; //The initialization vector.
    private static string strKey = "abcdefghijklmnmoabcdefghijklmnmo"; //The key used to encrypt the text.

    public static string Decrypt(string TextToDecrypt)
    {
        return Decryptor(TextToDecrypt);
    }

    private static string Encryptor(string TextToEncrypt)
    {
        //Turn the plaintext into a byte array.
        byte[] PlainTextBytes = System.Text.ASCIIEncoding.ASCII.GetBytes(TextToEncrypt);            

        //Setup the AES providor for our purposes.
        AesCryptoServiceProvider aesProvider = new AesCryptoServiceProvider();
        aesProvider.Key = System.Text.Encoding.ASCII.GetBytes(strKey);
        aesProvider.IV = System.Text.Encoding.ASCII.GetBytes(strIV);
        aesProvider.BlockSize = 128;
        aesProvider.KeySize = 256;            
        aesProvider.Padding = PaddingMode.PKCS7;
        aesProvider.Mode = CipherMode.CBC;

        ICryptoTransform cryptoTransform = aesProvider.CreateEncryptor(aesProvider.Key, aesProvider.IV);            
        byte[] EncryptedBytes = cryptoTransform.TransformFinalBlock(PlainTextBytes, 0, PlainTextBytes.Length);
        return Convert.ToBase64String(EncryptedBytes);                        
    }

    private static string Decryptor(string TextToDecrypt)
    {
        byte[] EncryptedBytes = Convert.FromBase64String(TextToDecrypt);

        //Setup the AES provider for decrypting.            
        AesCryptoServiceProvider aesProvider = new AesCryptoServiceProvider();
        aesProvider.Key = System.Text.Encoding.ASCII.GetBytes(strKey);
        aesProvider.IV = System.Text.Encoding.ASCII.GetBytes(strIV);
        aesProvider.BlockSize = 128;
        aesProvider.KeySize = 256;            
        aesProvider.Padding = PaddingMode.PKCS7;
        aesProvider.Mode = CipherMode.CBC;

        ICryptoTransform cryptoTransform = aesProvider.CreateDecryptor(aesProvider.Key, aesProvider.IV);
        byte[] DecryptedBytes = cryptoTransform.TransformFinalBlock(EncryptedBytes, 0, EncryptedBytes.Length);
        return System.Text.Encoding.ASCII.GetString(DecryptedBytes);
    }
}
A: 

You need to set the BlockSize and the KeySize before you set the Key and the IV. Additionally you should probably be generating a random IV for each message and note that ICryptoTransform implements IDisposable so these objects should be disposed.

Dave
This was the response that solved my problem. Everybody was really helpful. It would have took me awhile to realize that setting those properties were order dependent. Thanks Dave!