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Tuesday, March 31, 2015

AES 256 bits Encryption & Decryption

To Encrypt or decrypt value using AES algorithm use following functions:

1. Encryption:

        /// <summary>
        /// encrypt string using AES algo
        /// </summary>
        /// <param name="data">data string to encrypt</param>
        /// <returns>encrypted string</returns>
        public static string GetEncryptedDataAES(string data)
        {
            AesManaged aesManaged = new AesManaged();
            UTF8Encoding utf8 = new UTF8Encoding();
            aesManaged.Key = utf8.GetBytes("<Encrypttionkey>");
            aesManaged.IV = utf8.GetBytes("<initializationvectorKey>");
            // Encrypt the string to an array of bytes.
            byte[] encrypted = EncryptStringToBytesAES(data, aesManaged.Key, aesManaged.IV);
            data = Convert.ToBase64String(encrypted);
            data = HttpContext.Current.Server.UrlEncode(data);
            return data;
        }
        /// <summary>
        ///  encrypt string to byte using AES algo
        /// </summary>
        /// <param name="plainText">sring to encrypt</param>
        /// <param name="Key"> encrypt key</param>
        /// <param name="IV">Initialization vector</param>
        /// <returns>byte array of encrypt string</returns>
        static byte[] EncryptStringToBytesAES(string plainText, byte[] Key, byte[] IV)
        {
            // Check arguments.
            if (plainText == null || plainText.Length <= 0)
                throw new ArgumentNullException("plainText");
            if (Key == null || Key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (IV == null || IV.Length <= 0)
                throw new ArgumentNullException("IV");
            // Declare the stream used to encrypt to an in memory
            // array of bytes.
            MemoryStream msEncrypt = null;
            // Declare the AesManaged object
            // used to encrypt the data.
            AesManaged aesAlg = null;
            try
            {
                // Create a AesManaged object
                // with the specified key and IV.
                aesAlg = new AesManaged();
                aesAlg.Key = Key;
                aesAlg.IV = IV;
                // Create an encryptor to perform the stream transform.
                ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);
                // Create the streams used for encryption.
                msEncrypt = new MemoryStream();
                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                {
                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                    {
                        //Write all data to the stream.
                        swEncrypt.Write(plainText);
                    }
                }
            }
            finally
            {
                // Clear the AesManaged object.
                if (aesAlg != null)
                    aesAlg.Clear();
            }
            // Return the encrypted bytes from the memory stream.
            return msEncrypt.ToArray();
        }

------------------------------------------------------------------------------------------------------------------------------
2. Decryption:

        /// <summary>
        /// decrypt the encrypted string using AES
        /// </summary>
        /// <param name="data">string to decrypt</param>
        /// <returns>decrypted string </returns>
        public static string GetDecryptedDataAES(string data)
        {
            byte[] dataBytes = Convert.FromBase64String(data);
            AesManaged aesManaged = new AesManaged();
            UTF8Encoding utf8 = new UTF8Encoding();
            aesManaged.Key = utf8.GetBytes("<Encrypttionkey>");
            aesManaged.IV = utf8.GetBytes("<initializationvectorKey>");
            data = DecryptStringFromBytesAES(dataBytes, aesManaged.Key, aesManaged.IV);
            return data;
        }
     
        /// <summary>
        /// decrypt encrypted string from byte using AES algo
        /// </summary>
        /// <param name="cipherText">byte array to decrypt</param>
        /// <param name="Key"> encrypt key</param>
        /// <param name="IV">Initialization vector</param>
        /// <returns>decrypted string </returns>
        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.
            AesManaged aesAlg = null;
            // Declare the string used to hold
            // the decrypted text.
            string plaintext = null;
            try
            {
                // Create a AesManaged object
                // with the specified key and IV.
                aesAlg = new AesManaged();
                aesAlg.Key = Key;
                aesAlg.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();
                    }
                }
            }
            finally
            {
                // Clear the AesManaged object.
                if (aesAlg != null)
                    aesAlg.Clear();
            }
            return plaintext;
        }

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