Question

I was able to put together a encryption sample like below but during decryption i get invalid data(Exception). How am i supposed to decrypt

Encryption Method

public static string EncryptWithAes(string plainText, byte[] key, byte[] initiationVector)
        {

            byte[] cryptoBytes = Encoding.UTF8.GetBytes(plainText);

            using (RijndaelManaged aesAlgorithm = new RijndaelManaged())
            {
                aesAlgorithm.Key = key;
                aesAlgorithm.IV = initiationVector;
                aesAlgorithm.Mode = CipherMode.ECB;
                using (ICryptoTransform encryptoTransform = aesAlgorithm.CreateEncryptor(aesAlgorithm.Key, aesAlgorithm.IV))
                {
                    cryptoBytes = encryptoTransform.TransformFinalBlock(cryptoBytes, 0, cryptoBytes.Length);
                }
            }
            return Convert.ToBase64String(cryptoBytes);
        }

Decryption Method

 public static string DecryptAesCryptoString(string cipherText, byte[] key, byte[] initiationVector)
        {
            byte[] decryptedByte;
            using (RijndaelManaged aesAlgorithm = new RijndaelManaged())
            {
                aesAlgorithm.Key = key;
                aesAlgorithm.IV = initiationVector;
                aesAlgorithm.Mode = CipherMode.ECB;

                using (ICryptoTransform decryptoTransform = aesAlgorithm.CreateDecryptor(aesAlgorithm.Key, aesAlgorithm.IV))
                {
                    byte[] cipherBytes = Convert.FromBase64String(cipherText);
                    decryptedByte = decryptoTransform.TransformFinalBlock(cipherBytes, 0, cipherBytes.Length);

                }
            }
            return Encoding.UTF8.GetString(decryptedByte);
        }

i think the problem is with all the encoding that are going inside these methods

Sample Data

plainText = stackoverflow

base64encoded Key = B8Y/6doxwqU870C6jzYWhsr3hKSLokAOkkLCDiy+TS4=
(should be easy to convert to bytes ain’t it)

base64encoded IV = NZIpD60eBmdsOFFhA2bfvw==

encryptedValue = 77+977+977+977+977+9Ce+/ve+/vQ3vv70F77+9UzHvv73vv70=

I provide same encrypted value , IV and Key to decrypt to Stackoverflow

Answer 1

and sadly this was certainly due to the Encoding problem. Now solved it like below

Encryption

public static string EncryptWithAes(string plainText, byte[] key, byte[] initiationVector)
        {
            byte[] cryptoBytes = Convert.FromBase64String(plainText);
            using (RijndaelManaged aesAlgorithm = new RijndaelManaged())
            {
                aesAlgorithm.Key = key;
                aesAlgorithm.IV = initiationVector;
                aesAlgorithm.Mode = CipherMode.ECB;
                using (ICryptoTransform encryptoTransform = aesAlgorithm.CreateEncryptor(aesAlgorithm.Key, aesAlgorithm.IV))
                {
                    cryptoBytes = encryptoTransform.TransformFinalBlock(cryptoBytes, 0, cryptoBytes.Length);
                }
            }
            return Convert.ToBase64String(cryptoBytes);
        }

Decryption

public static string DecryptAesCryptoString(string cipherText, byte[] key, byte[] initiationVector)
{

    byte[] decryptedByte;
    using (RijndaelManaged aesAlgorithm = new RijndaelManaged())
    {
        aesAlgorithm.Key = key;
        aesAlgorithm.IV = initiationVector;
        aesAlgorithm.Mode = CipherMode.ECB;
        using (ICryptoTransform decryptoTransform = aesAlgorithm.CreateDecryptor(aesAlgorithm.Key, aesAlgorithm.IV))
        {
            byte[] cipherBytes = Convert.FromBase64String(cipherText);
            decryptedByte = decryptoTransform.TransformFinalBlock(cipherBytes, 0, cipherBytes.Length);

        }
    }
    return Convert.ToBase64String(decryptedByte);
}