C# DES 암호화 + Base64

프로그래밍/C# & ASP.NET 2.0 2012. 6. 7. 17:13

DES 암호화나 Base64 에 대한 설명은 하지않겠습니다.(구글이나 네이버 검색하세요. ^^ )

CBC 와 PKCS7 에 대한 설명은 http://blog.cjred.net/141 를 참고하세요.

using System.Security.Cryptography

namespace crypto{
    class DES{
        byte[] desKey;
        byte[] desVector;

public DES(string key, string vector)
        {
            // key와 vector 값을 byte[] 형으로 변환시킵니다.
            this.desKey = System.Text.Encoding.Default.GetBytes(key);
            this.desVector = System.Text.Encoding.Default.GetBytes(vector);

if (this.desVector.Length != 8)
            {
                // DES 암호화키는 8자리입니다.
                throw (new Exception("Invalid key. Key length must be 8 byte."));
            }

// DES 암호화 관련 클래스를 생성합니다.
            DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
            // cipher 모드를 CBC 방식으로 사용합니다.
            cryptoProvider.Mode = CipherMode.CBC;
            // Padding Mode 를 PKCS7 으로 사용합니다.(PKCS5 와 동일합니다.)
            cryptoProvider.Padding = PaddingMode.PKCS7;
        }

public string Encrypt(string plainText)
        {
            if (string.IsNullOrEmpty(plainText))
            {
                throw new ArgumentException("the string which needs to be encrypted can not be null.");
            }
            
            MemoryStream memoryStream = new MemoryStream();
            CryptoStream cryptoStream = new CryptoStream(memoryStream, cryptoProvider.CreateEncryptor(key, vector), CryptoStreamMode.Write);
            StreamWriter writer = new StreamWriter(cryptoStream, Encoding.Default);
           
            writer.Write(plainText);
            writer.Flush();
            cryptoStream.FlushFinalBlock();
            writer.Flush();

UTF8Encoding utf8Enc = new UTF8Encoding();
            String cypherText = Convert.ToBase64String(memoryStream.GetBuffer(), 0, (int)memoryStream.Length);
            return cypherText;
        }

public string Decrypt(string cypherText)
        {
            string plainText;
            if (string.IsNullOrEmpty(cypherText))
            {
                throw new ArgumentException("the string which needs to be encrypted can not be null.");
            }
           
            MemoryStream memoryStream = new MemoryStream(Convert.FromBase64String(cypherText));
            CryptoStream cryptoStream = new CryptoStream(memoryStream, cryptoProvider.CreateDecryptor(key, vector), CryptoStreamMode.Read);
            StreamReader reader = new StreamReader(cryptoStream);

plainText = reader.ReadToEnd();
            return plainText;
        }

static void Main(string[] args)
        {
            DES des = new DES("kyString","123456");
            string cypherText = des.Encrypt("test string");
            console.WriteLine(cypherText);

string plainText = des.Decrypt(cypherText);
            console.WriteLine(plainText);
        }
    }
}