C# DES 암호화(Encrypt), 복호화(Decrypt)

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// 암호화 키(8byte)

static byte[] desKey = ASCIIEncoding.ASCII.GetBytes("tech0001");

Des des = new Des(desKey);

.......

Des Class(암호화, 복호화)

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Security.Cryptography;

using System.IO;

/// <summary>

/// Summary description for Des

/// </summary>

public class Des

{

    byte[] key = null;

protected Des()

{

}

    public Des(byte[] desKey)

    {

        this.key = desKey;

    }

    public string Encrypt(string plain_text)

    {

        if (string.IsNullOrEmpty(plain_text))

        {

            throw new ArgumentException("The string which needs to be encrypted can not be null.");

        }

        if (key.Length != 8)

        {

            throw (new Exception("Invalid key. Key length must be 8 byte."));

        }

        DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();

        MemoryStream memoryStream = new MemoryStream();

        CryptoStream cryptoStream = new CryptoStream(memoryStream,

            cryptoProvider.CreateEncryptor(key, key), CryptoStreamMode.Write);

        StreamWriter writer = new StreamWriter(cryptoStream);

        writer.Write(plain_text);

        writer.Flush();

        cryptoStream.FlushFinalBlock();

        writer.Flush();

        string cypher_text = Convert.ToBase64String(memoryStream.GetBuffer(), 0, (int)memoryStream.Length);

        return cypher_text;

    }

    public string Decrypt(string cypher_text)

    {

        if (String.IsNullOrEmpty(cypher_text))

        {

            throw new ArgumentNullException

               ("The string which needs to be decrypted can not be null.");

        }

        if (key.Length != 8)

        {

            throw (new Exception("Invalid key. Key length must be 8 byte."));

        }

        DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();

        MemoryStream memoryStream = new MemoryStream

                (Convert.FromBase64String(cypher_text));

        CryptoStream cryptoStream = new CryptoStream(memoryStream,

            cryptoProvider.CreateDecryptor(key, key), CryptoStreamMode.Read);

        StreamReader reader = new StreamReader(cryptoStream);

        string plain_text = reader.ReadToEnd();

        return plain_text;

    }

}