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3DES
鎖定
- 中文名
- 3DES
- 外文名
- Triple DES
- 發明者
- 美國
- 發明時間
- 1981年
3DES算法介紹
DES使用56位密鑰和密碼塊的方法,而在密碼塊的方法中,文本被分成64位大小的文本塊然後再進行加密。比起最初的DES,3DES更為安全。
3DES(即Triple DES)是DES向AES過渡的加密算法(1999年,NIST將3-DES指定為過渡的加密標準),加密算法,其具體實現如下:設Ek()和Dk()代表DES算法的加密和解密過程,K代表DES算法使用的密鑰,P代表明文,C代表密文,這樣:
3DES加密過程為:C=Ek3(Dk2(Ek1(P)))
3DES解密過程為:P=Dk1(EK2(Dk3(C)))
3DES歷史發展
它以DES為基本模塊,通過組合分組方法設計出分組加密算法。比起最初的DES,3DES更為安全。
3DES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/解密過下所示。
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麼高,K1可以等於K3。在這種情況下,密鑰的有效長度為112位。
3DES3DES算法
3DES算法是指使用雙長度(16字節)密鑰K=(KL||KR)將8字節明文數據塊進行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[16], BYTE Data[8], BYTE Out[8])
{
BYTE Buf1[8], Buf2[8];
DES (&DoubleKeyStr[0], Data, Buf1);
UDES(&DoubleKeyStr[8], Buf1, Buf2);
DES (&DoubleKeyStr[0], Buf2, Out);
}
3DES加密標準
1999年,NIST將3-DES指定為過渡的加密標準。
3DES加密實例
3DESJava語言
/*字符串 DESede(3DES) 加密*/ //注:百度代碼識別BUG,代碼中空格屬全角。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字節 // 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字節 // 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; } // 轉換成十六進制字符串 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字節的密鑰 String szSrc = "This is a 3DES test. 測試"; System.out.println("加密前的字符串:" + szSrc); byte[] encoded = encryptMode(keyBytes, szSrc.getBytes()); System.out.println("加密後的字符串:" + new String(encoded)); byte[] srcBytes = decryptMode(keyBytes, encoded); System.out.println("解密後的字符串:" + (new String(srcBytes))); } }
3DESPHP語言
class Mycrypt3des { var $CI; public $key = "keystring"; /*構造方法*/ function __construct() { $this->CI =& get_instance(); } public function encrypt($input) { // 數據加密 if (empty($input)){ return null; } $size = mcrypt_get_block_size ( MCRYPT_3DES, 'ecb' ); $input = $this->pkcs5_pad ( $input, $size ); $key = str_pad ( $this->key, 24, '0' ); $td = mcrypt_module_open ( MCRYPT_3DES, '', 'ecb', '' ); $iv = @mcrypt_create_iv ( mcrypt_enc_get_iv_size ( $td ), MCRYPT_RAND ); @mcrypt_generic_init ( $td, $key, $iv ); $data = mcrypt_generic ( $td, $input ); mcrypt_generic_deinit ( $td ); mcrypt_module_close ( $td ); $data = base64_encode ( $data ); return $data; } public function decrypt($encrypted) { // 數據解密 if (!$encrypted || empty($encrypted)){ return null; } $encrypted = base64_decode ( $encrypted ); if (!$encrypted || empty($encrypted)){ return null; } $key = str_pad ( $this->key, 24, '0' ); $td = mcrypt_module_open ( MCRYPT_3DES, '', 'ecb', '' ); $iv = @mcrypt_create_iv ( mcrypt_enc_get_iv_size ( $td ), MCRYPT_RAND ); $ks = mcrypt_enc_get_key_size ( $td ); @mcrypt_generic_init ( $td, $key, $iv ); $decrypted = mdecrypt_generic ( $td, $encrypted ); mcrypt_generic_deinit ( $td ); mcrypt_module_close ( $td ); $y = $this->pkcs5_unpad ( $decrypted ); return $y; } function pkcs5_pad($text, $blocksize) { $pad = $blocksize - (strlen ( $text ) % $blocksize); return $text . str_repeat ( chr ( $pad ), $pad ); } function pkcs5_unpad($text) { $pad = ord ( $text {strlen ( $text ) - 1} ); if ($pad > strlen ( $text )) { return false; } if (strspn ( $text, chr ( $pad ), strlen ( $text ) - $pad ) != $pad) { return false; } return substr ( $text, 0, - 1 * $pad ); } function PaddingPKCS7($data) { $block_size = mcrypt_get_block_size ( MCRYPT_3DES, MCRYPT_MODE_CBC ); $padding_char = $block_size - (strlen ( $data ) % $block_size); $data .= str_repeat ( chr ( $padding_char ), $padding_char ); return $data; } }