加密過程
3DES加密過程為：C=Ek3(Dk2(Ek1(P)))
3DES解密過程為：P=Dk1((EK2(Dk3(C)))
具體的加/解密過程如圖所示。
using System;
using System.Text;
using System. IO;
using System.Security.Cryptography;
class Class1
{
static void Main()
{
Console.WriteLine("Encrypt String...");
txtKey = "tkGGRmBErvc=";
btnKeyGen();
Console.WriteLine("Encrypt Key :{0}",txtKey);
txtIV = "Kl7ZgtM1dvQ=";
btnIVGen();
Console.WriteLine("Encrypt IV :{0}",txtIV);
Console.WriteLine();
string txtEncrypted = EncryptString("1111");
Console.WriteLine("Encrypt String : {0}",txtEncrypted);
string txtOriginal = DecryptString(txtEncrypted);
Console.WriteLine("Decrypt String : {0}",txtOriginal);
}
private static SymmetricAlgorithm mCSP;
private static string txtKey;
private static string txtIV;
private static void btnKeyGen()
{
mCSP = SetEnc();
byte[] byt2 = Convert.FromBase64String(txtKey);
mCSP.Key = byt2;
}
private static void btnIVGen()
{
byte[] byt2 = Convert.FromBase64String(txtIV);
mCSP.IV = byt2;
}
private static string EncryptString(string Value)
{
ICryptoTransform ct;
MemoryStream ms;
CryptoStream cs;
byte[] byt;
ct = mCSP.CreateEncryptor(mCSP.Key, mCSP.IV);
byt = Encoding.UTF8.GetBytes(Value);
ms = new MemoryStream();
cs = new CryptoStream(ms, ct, CryptoStreamMode.Write);
cs.Write(byt, 0, byt.Length);
cs.FlushFinalBlock();
cs.Close();
return Convert.ToBase64String(ms.ToArray());
}
private static string DecryptString(string Value)
{
ICryptoTransform ct;
MemoryStream ms;
CryptoStream cs;
byte[] byt;
ct = mCSP.CreateDecryptor(mCSP.Key, mCSP.IV);
byt = Convert.FromBase64String(Value);
ms = new MemoryStream();
cs = new CryptoStream(ms, ct, CryptoStreamMode.Write);
cs.Write(byt, 0, byt.Length);
cs.FlushFinalBlock();
cs.Close();
return Encoding.UTF8.GetString(ms.ToArray());
}
private static SymmetricAlgorithm SetEnc()
{
return new DESCryptoServiceProvider();
}
}
K1、K2、K3決定了算法的安全性，若三個密鑰互不相同，本質上就相當於用一個長為168位的密鑰進行加密。多年來，它在對付強力攻擊時是比較安全的。若數據對安全性要求不那么高，K1可以等於K3。在這種情況下，密鑰的有效長度為112位。
DES算法
3DES算法是指使用雙長度（16位元組）密鑰K=（KL||KR）將8位元組明文數據塊進行3次DES加密/解密。如下所示：
Y = DES( KL[DES-1( KR[DES( KL[X] )] )] )
解密方式為：
X = DES-1( KL[DES( KR[DES-1( KL[Y] )] )] )
其中，DES( KL[X] )表示用密鑰K對數據X進行DES加密，DES-1( KR[Y] )表示用密鑰K對數據Y進行解密。
SessionKey的計算採用3DES算法，計算出單倍長度的密鑰。表示法為:SK = Session(DK，DATA)
3DES加密算法為：
VOID 3DES(BYTE DoubleKeyStr， BYTE Data， BYTE Out)
{
BYTE Buf1， Buf2;
DES (&DoubleKeyStr， Data， Buf1);
UDES(&DoubleKeyStr， Buf1， Buf2);
DES (&DoubleKeyStr， Buf2， Out);
}
加密實例
Java語言
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 | /*字元串 DESede(3DES) 加密*/ //註：百度代碼識別BUG，代碼中空格屬全形。拷貝代碼之後請自行修改。 import java.security.Security; import javax.crypto.Cipher; import javax.crypto.SecretKey; import javax.crypto.spec.SecretKeySpec; public class DES3 { private static final String Algorithm = "DESede"; // 定義 加密算法 ,可用 // DES,DESede,Blowfish // keybyte為加密 密鑰 ，長度為24位元組 // src為被加密的 數據緩衝區 （源） public static byte[] encryptMode(byte[] keybyte, byte[] src) { try { // 生成密鑰 SecretKey deskey = new SecretKeySpec(keybyte, Algorithm); // 加密 Cipher c1 = Cipher.getInstance(Algorithm); c1.init(Cipher.ENCRYPT_MODE, deskey); return c1.doFinal(src); } catch (java.security.NoSuchAlgorithmException e1 ) { e1.printStackTrace(); } catch (javax.crypto.NoSuchPaddingException e2) { e2.printStackTrace(); } catch (java.lang.Exception e3) { e3.printStackTrace(); } return null; } // keybyte為加密密鑰，長度為24位元組 // src為加密後的緩衝區 public static byte[] decryptMode(byte[] keybyte, byte[] src) { try { // 生成密鑰 SecretKey deskey = new SecretKeySpec(keybyte, Algorithm); // 解密 Cipher c1 = Cipher.getInstance(Algorithm); c1.init(Cipher.DECRYPT_MODE, deskey); return c1.doFinal(src); } catch (java.security.NoSuchAlgorithmException e1) { e1.printStackTrace(); } catch (javax.crypto.NoSuchPaddingException e2) { e2.printStackTrace(); } catch (java.lang.Exception e3) { e3.printStackTrace(); } return null; } // 轉換成 十六進制 字元串 public static String byte2hex(byte[] b) { String hs = ""; String stmp = ""; for (int n = 0; n < b.length; n++) { stmp = (java.lang.Integer.toHexString(b[n] & 0XFF)); if (stmp.length() == 1) { hs = hs + "0" + stmp; } else { hs = hs + stmp; } if (n < b.length - 1) { hs = hs + ":"; } } return hs.toUpperCase(); } public static void main (String[] args) { // 添加新安全算法,如果用JCE就要把它添加進去 Security.addProvider(new com.sun.crypto.provider.SunJCE()); final byte[] keyBytes = {0x11, 0x22, 0x4F, 0x58, (byte) 0x88, 0x10, 0x40, 0x38, 0x28, 0x25, 0x79, 0x51, (byte) 0xCB, (byte) 0xDD, 0x55, 0x66, 0x77, 0x29, 0x74, (byte) 0x98, 0x30, 0x40, 0x36, (byte) 0xE2}; // 24位元組的密鑰 String szSrc = "This is a 3DES test . 測試"; System.out.println("加密前的字元串:" + szSrc); byte[] encoded = encryptMode(keyBytes, szSrc.getBytes()); System.out.println("加密後的字元串:" + new String(encoded)); byte[] srcBytes = decryptMode(keyBytes, encoded); System.out.println("解密後的字元串:" + (new String(srcBytes))); } } |
