using System;

using System.Text;

using System.IO;

using System.Security.Cryptography;

​

class DataCryptor : IDisposable {

    Aes     aes = null;

    bool    disposed = false;

​

​

    public DataCryptor() {

        // 이 코드는 new AesManaged(); 로도 변경이 가능합니다.

        // aes = new AesManaged();

        aes = Aes.Create();

    }

​

    // ABCDEFGHABCDEFGHABCDEFGHABCDEFGH 입니다.

    static byte[] DefaultKey = {

        0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,

        0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,

        0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,

        0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,

    };

    // 0123456701234567 입니다.

    static byte[] DefaultIV  = {

        0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,

        0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37

    };

​

    public byte[] Encrypt(byte[] b, byte[] key, byte[] iv) {

        // 데이터가 입력되지 않으면 예외를 발생시키고,

        // 키나 IV가 입력되지 않으면 기본 값을 사용합니다.

        if (b == null || b.Length == 0) throw new ArgumentException();

        if (key == null || key.Length == 0) key = DefaultKey;

        if (iv == null || iv.Length == 0) iv = DefaultIV;

​

        // #1

        aes.Key = key;

        aes.IV = iv;

​

        // #2

        ICryptoTransform transform = aes.CreateEncryptor();

        MemoryStream result = new MemoryStream();

​

        // #3

        using (CryptoStream cs = new CryptoStream(result, transform, CryptoStreamMode.Write)) {

            int ofs = 0;

            int bufsize = 4096;

​

            while ( ofs < b.Length ) {

                int c = b.Length - ofs;

                if (c > bufsize) c = bufsize;

                cs.Write(b, ofs, c);

                ofs += bufsize;

            }

        }

        transform.Dispose();

        return result.ToArray();

    }

​

    public byte[] Decrypt(byte[] b, byte[] key, byte[] iv) {

        if (b == null || b.Length == 0) throw new ArgumentException();

        if (key == null || key.Length == 0) key = DefaultKey;

        if (iv == null || iv.Length == 0) iv = DefaultIV;

        aes.Key = key;

        aes.IV = iv;

        ICryptoTransform transform = aes.CreateDecryptor();

        MemoryStream data = new MemoryStream(b);

        MemoryStream result = new MemoryStream();

​

        using (CryptoStream cs = new CryptoStream(data, transform, CryptoStreamMode.Read)) {

            int bufsize = 4096;

            byte[] buf = new byte[4096];

            // 암호 스트림에서 데이터를 읽습니다.

            int nRead = cs.Read(buf, 0, bufsize);

​

            // 데이터를 읽어왔다면,

            while (nRead > 0 ) {

                // 읽은 데이터만큼 결과를 저장할 스트림에 쓰고,

                // 다시 암호 스트림에서 데이터를 읽습니다.

                result.Write(buf, 0, nRead);

                nRead = cs.Read(buf, 0, bufsize);

            }

        }

​

        transform.Dispose();

        result.Dispose();

        return result.ToArray();

    }

    public void Dispose() {

        if (disposed) return;

        aes.Dispose();

        disposed = true;

    }

}

​

public class Program {

    public static void Main(string[] args) {

        DataCryptor dc = new DataCryptor();

        byte[] data = Encoding.ASCII.GetBytes("Encryption example in C# Application");

        Console.WriteLine("Before Encrypt");

        Console.WriteLine("  Raw   : {0}", Encoding.ASCII.GetString(data));

        Console.WriteLine("  Base64: {0}", Convert.ToBase64String(data));

        Console.WriteLine();

        data = dc.Encrypt(data, null, null);

        Console.WriteLine("After Encrypt");

        Console.WriteLine("  Raw   : {0}", Encoding.ASCII.GetString(data));

        Console.WriteLine("  Base64: {0}", Convert.ToBase64String(data));

        Console.WriteLine();

        data = dc.Decrypt(data, null, null);

        Console.WriteLine("And Decrypt the encrypted data");

        Console.WriteLine("  Raw   : {0}", Encoding.ASCII.GetString(data));

        Console.WriteLine("  Base64: {0}", Convert.ToBase64String(data));

    }

}