Java加密算法DES详解编程语言

密钥加密也称为对称加密，速度快，但加密和解密的钥匙必须相同，只有通信双方才能知道钥匙。

import java.security.Key;   
import java.security.SecureRandom;   
   
import javax.crypto.Cipher;   
import javax.crypto.KeyGenerator;   
import javax.crypto.SecretKey;   
import javax.crypto.SecretKeyFactory;   
import javax.crypto.spec.DESKeySpec;   
import javax.crypto.spec.IvParameterSpec;   
   
/**  
 * DES 算法       1972美国IBM研制，对称加密算法  
 * @author stone  
 * @date 2014-03-10 04:47:05  
 */   
public class DES {     
    // 算法名称   
    public static final String KEY_ALGORITHM = "DES";   
    // 算法名称/加密模式/填充方式   
    public static final String CIPHER_ALGORITHM_ECB = "DES/ECB/PKCS5Padding";   
    public static final String CIPHER_ALGORITHM_CBC = "DES/CBC/PKCS5Padding";   
       
    public static void main(String[] args) throws Exception {   
        /*  
         * 使用 ECB mode  
         * 密钥生成器 生成密钥  
         * ECB mode cannot use IV  
         */   
        byte[] key = generateKey();    
        byte[] encrypt = encrypt("胃炎F#*（x）".getBytes(), key);   
        System.out.println(new String(decrypt(encrypt, key)));   
           
           
        /*  
         * 使用CBC mode  
         * 使用密钥工厂生成密钥，加密 解密  
         * iv: DES in CBC mode and RSA ciphers with OAEP encoding operation.  
         */   
        DESKeySpec dks = new DESKeySpec(generateKey());   
        SecretKeyFactory factory = SecretKeyFactory.getInstance(KEY_ALGORITHM);   
        SecretKey secretKey = factory.generateSecret(dks);   
        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM_CBC);   
        cipher.init(Cipher.ENCRYPT_MODE, secretKey, new IvParameterSpec(getIV()));   
        byte[] enc = cipher.doFinal("胃炎A%F#*（x）".getBytes()); //加密   
           
        cipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(getIV()));   
        byte[] dec = cipher.doFinal(enc); // 解密   
        System.out.println(new String(dec));   
    }   
       
    static byte[] getIV() {   
        String iv = "asdfivh7"; //IV length: must be 8 bytes long   
        return iv.getBytes();   
    }   
   
    /**  
     * 生成密钥  
     *   
     * @return  
     * @throws Exception  
     */   
    private static byte[] generateKey() throws Exception {   
        KeyGenerator keyGenerator = KeyGenerator.getInstance(KEY_ALGORITHM);   
        keyGenerator.init(56); //des 必须是56, 此初始方法不必须调用   
        SecretKey secretKey = keyGenerator.generateKey();   
        return secretKey.getEncoded();   
    }   
   
    /**  
     * 还原密钥  
     *   
     * @param key  
     * @return  
     * @throws Exception   
     */   
    private static Key toKey(byte[] key) throws Exception {   
        DESKeySpec des = new DESKeySpec(key);   
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(KEY_ALGORITHM);   
        SecretKey secretKey = keyFactory.generateSecret(des);   
        return secretKey;   
    }   
       
    /**  
     * 加密   
     * @param data 原文  
     * @param key  
     * @return 密文  
     * @throws Exception  
     */   
    public static byte[] encrypt(byte[] data, byte[] key) throws Exception {   
        Key k = toKey(key);   
        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM_ECB);   
        cipher.init(Cipher.ENCRYPT_MODE, k, new SecureRandom());   
        return cipher.doFinal(data);   
    }   
    /**  
     * 解密  
     * @param data 密文  
     * @param key  
     * @return 明文、原文  
     * @throws Exception  
     */   
    public static byte[] decrypt(byte[] data, byte[] key) throws Exception {   
        Key k = toKey(key);   
        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM_ECB);   
        cipher.init(Cipher.DECRYPT_MODE, k, new SecureRandom());   
        return cipher.doFinal(data);   
    }   
}