<h3> [ C# ] String 스트링 암호화 복호화 </h3>

String스트링 암호화 복호화

public class Crypto

{

    private static byte[] _salt = Encoding.ASCII.GetBytes("o6806642kbM7c5");

    /// <summary>

    /// Encrypt the given string using AES.  The string can be decrypted using

    /// DecryptStringAES().  The sharedSecret parameters must match.

    /// </summary>

    /// <param name="plainText">The text to encrypt.</param>

    /// <param name="sharedSecret">A password used to generate a key for encryption.</param>

    public static string EncryptStringAES(string plainText, string sharedSecret)

    {

        if (string.IsNullOrEmpty(plainText))

            throw new ArgumentNullException("plainText");

        if (string.IsNullOrEmpty(sharedSecret))

            throw new ArgumentNullException("sharedSecret");

        string outStr = null;                       // Encrypted string to return

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

        try

        {

            // generate the key from the shared secret and the salt

            Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(sharedSecret, _salt);

            // Create a RijndaelManaged object

            aesAlg = new RijndaelManaged();

            aesAlg.Key = key.GetBytes(aesAlg.KeySize / 8);

            // Create a decryptor to perform the stream transform.

            ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

            // Create the streams used for encryption.

            using (MemoryStream msEncrypt = new MemoryStream())

            {

                // prepend the IV

                msEncrypt.Write(BitConverter.GetBytes(aesAlg.IV.Length), 0, sizeof(int));

                msEncrypt.Write(aesAlg.IV, 0, aesAlg.IV.Length);

                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))

                {

                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))

                    {

                        //Write all data to the stream.

                        swEncrypt.Write(plainText);

                    }

                }

                outStr = Convert.ToBase64String(msEncrypt.ToArray());

            }

        }

        finally

        {

            // Clear the RijndaelManaged object.

            if (aesAlg != null)

                aesAlg.Clear();

        }

        // Return the encrypted bytes from the memory stream.

        return outStr;

    }

    /// <summary>

    /// Decrypt the given string.  Assumes the string was encrypted using

    /// EncryptStringAES(), using an identical sharedSecret.

    /// </summary>

    /// <param name="cipherText">The text to decrypt.</param>

    /// <param name="sharedSecret">A password used to generate a key for decryption.</param>

    public static string DecryptStringAES(string cipherText, string sharedSecret)

    {

        if (string.IsNullOrEmpty(cipherText))

            throw new ArgumentNullException("cipherText");

        if (string.IsNullOrEmpty(sharedSecret))

            throw new ArgumentNullException("sharedSecret");

        // Declare the RijndaelManaged object

        // used to decrypt the data.

        RijndaelManaged aesAlg = null;

        // Declare the string used to hold

        // the decrypted text.

        string plaintext = null;

        try

        {

            // generate the key from the shared secret and the salt

            Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(sharedSecret, _salt);

            // Create the streams used for decryption.               

            byte[] bytes = Convert.FromBase64String(cipherText);

            using (MemoryStream msDecrypt = new MemoryStream(bytes))

            {

                // Create a RijndaelManaged object

                // with the specified key and IV.

                aesAlg = new RijndaelManaged();

                aesAlg.Key = key.GetBytes(aesAlg.KeySize / 8);

                // Get the initialization vector from the encrypted stream

                aesAlg.IV = ReadByteArray(msDecrypt);

                // Create a decrytor to perform the stream transform.

                ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

                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 RijndaelManaged object.

            if (aesAlg != null)

                aesAlg.Clear();

        }

        return plaintext;

    }

    private static byte[] ReadByteArray(Stream s)

    {

        byte[] rawLength = new byte[sizeof(int)];

        if (s.Read(rawLength, 0, rawLength.Length) != rawLength.Length)

        {

            throw new SystemException("Stream did not contain properly formatted byte array");

        }

        byte[] buffer = new byte[BitConverter.ToInt32(rawLength, 0)];

        if (s.Read(buffer, 0, buffer.Length) != buffer.Length)

        {

            throw new SystemException("Did not read byte array properly");

        }

        return buffer;

    }

}

http://stackoverflow.com/questions/202011/encrypt-and-decrypt-a-string