OpenSSL.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Security.Cryptography;

namespace Aes128Decrypt
{
     static class OpenSSL
    {
        public static string OpenSSLDecrypt(this string encrypted, byte[] key, byte[] iv)
        {
            // base 64 decode
            byte[] encryptedBytesWithSalt = Convert.FromBase64String(encrypted);
            // extract salt (first 8 bytes of encrypted)
            byte[] salt = new byte[8];



            byte[] encryptedBytes = new byte[encryptedBytesWithSalt.Length - salt.Length - 8];
            Buffer.BlockCopy(encryptedBytesWithSalt, 8, salt, 0, salt.Length);
            Buffer.BlockCopy(encryptedBytesWithSalt, salt.Length + 8, encryptedBytes, 0, encryptedBytes.Length);

            return DecryptStringFromBytesAes(encryptedBytesWithSalt, key, iv);
        }
        private static string DecryptStringFromBytesAes(byte[] cipherText, byte[] key, byte[] iv)
        {
            // Check arguments.
            if (cipherText == null || cipherText.Length <= 0)
                throw new ArgumentNullException("cipherText");
            if (key == null || key.Length <= 0)
                throw new ArgumentNullException("key");
            if (iv == null || iv.Length <= 0)
                throw new ArgumentNullException("iv");

            // Declare the RijndaelManaged object
            // used to decrypt the data.
            RijndaelManaged aesAlg = null;

            // Declare the string used to hold
            // the decrypted text.
            string plaintext;

            try
            {
                // Create a RijndaelManaged object
                // with the specified key and IV.
                aesAlg = new RijndaelManaged { Mode = CipherMode.CBC, KeySize = 256, BlockSize = 128, Key = key, IV = iv };

                // Create a decrytor to perform the stream transform.
                ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
                // Create the streams used for decryption.
                using (MemoryStream msDecrypt = new MemoryStream(cipherText))
                {
                    using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                    {
                        using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                        {
                            // Read the decrypted bytes from the decrypting stream
                            // and place them in a string.
                            plaintext = srDecrypt.ReadToEnd();
                            srDecrypt.Close();
                        }
                    }
                }
            }
            finally
            {
                // Clear the RijndaelManaged object.
                if (aesAlg != null)
                    aesAlg.Clear();
            }

            return plaintext;
        }


    }
}