java 实现加密

加密有单向加密和双向加密之分,也叫对称加密和非对称加密,双向加密就是把数据加密后,还可以解密成原来的数据,但是需要使用到密钥,而且必须是同一个密钥.才可以解密成原来的数据.一开始我也不知道,密钥是使用系统生成的密钥,加密和解密分开操作的时候,加密过后,数据就解密不出来了.java实现加密的方法有DES,AES,等这些对称加密.单向加密从严格的意义来讲不算加密.只是实现了一定的算法,但是不可以逆转.md5加密就是一个单向非对称加密的技术.直接上代码

package com.chen;import java.security.InvalidKeyException;import javax.crypto.BadPaddingException;import javax.crypto.Cipher;import javax.crypto.IllegalBlockSizeException;import javax.crypto.KeyGenerator;import javax.crypto.SecretKey;public class Chen {    // 密钥生成器    PRivate KeyGenerator kg = null;    // 密钥    private SecretKey key = null;    // 进行加密和解密    private Cipher cip = null;    public Chen() throws Exception{        kg = KeyGenerator.getInstance("DES");        key = kg.generateKey();        cip = Cipher.getInstance("DES");    }    public byte[] encrypt(byte[] s) throws InvalidKeyException, IllegalBlockSizeException, BadPaddingException{        // 初始化        cip.init(Cipher.ENCRYPT_MODE, key);        // 加密        return cip.doFinal(s);    }    public byte[] decrypt(byte[] b) throws InvalidKeyException, IllegalBlockSizeException, BadPaddingException{        // 初始化        cip.init(Cipher.DECRYPT_MODE, key);        // 解密        return cip.doFinal(b);    }    public static void main(String[] args) {        try {            Chen chen = new Chen();            String str = "aba萨芬斯蒂芬";            // 加密            byte[] temp = chen.encrypt(str.getBytes());            // 解密            byte[] flag = chen.decrypt(temp);            System.out.println("明文 : " + str);            System.out.println("加密后的数据 : " + new String(temp));            System.out.println("解密后的数据 : " + new String(flag));        } catch (Exception e) {            e.printStackTrace();        }    }}

AES加密和解密的代码

package crypt;import java.security.InvalidKeyException;import java.security.NoSuchAlgorithmException;import javax.crypto.BadPaddingException;import javax.crypto.Cipher;import javax.crypto.IllegalBlockSizeException;import javax.crypto.KeyGenerator;import javax.crypto.NoSuchPaddingException;import javax.crypto.SecretKey;public class AEScrypt {    //  key生成器    private KeyGenerator kg;    // 密钥    private SecretKey key;    // 加密解密类    private Cipher cipher;    public AEScrypt() throws NoSuchAlgorithmException, NoSuchPaddingException{        kg = KeyGenerator.getInstance("AES");        System.out.println(kg.getProvider().getName());        key = kg.generateKey();        cipher = Cipher.getInstance("AES");        System.out.println(cipher.getProvider());    }    public byte[] encrypt(byte[] b) throws InvalidKeyException, IllegalBlockSizeException, BadPaddingException{        // 初始化        cipher.init(Cipher.ENCRYPT_MODE, key);        return cipher.doFinal(b);    }    public byte[] decrypt(byte[] b) throws InvalidKeyException, IllegalBlockSizeException, BadPaddingException{        // 初始化        cipher.init(Cipher.DECRYPT_MODE, key);        // 解密        return cipher.doFinal(b);            }    public static void main(String[] args) {        try {            AEScrypt aes = new AEScrypt();            String s = "safasf的送饭饭2342(&((*";            byte[] temp = aes.encrypt(s.getBytes());            byte[] flag = aes.decrypt(temp);            System.out.println("明文 : " + s);            System.out.println("加密 : " + new String(temp));            System.out.println("解密 : " + new String(flag));        } catch (Exception e) {                        e.printStackTrace();        }            }}

非对称RSA,有连个密钥,一个公开密钥,一个私有密钥,通过其中一个密钥加密,在通过其他一个密钥解密

package crypt;import java.security.InvalidKeyException;  import java.security.KeyPair;  import java.security.KeyPairGenerator;  import java.security.NoSuchAlgorithmException;  import java.security.interfaces.RSAPrivateKey;  import java.security.interfaces.RSAPublicKey;    import javax.crypto.BadPaddingException;  import javax.crypto.Cipher;  import javax.crypto.IllegalBlockSizeException;  import javax.crypto.NoSuchPaddingException;    public class RSAcrypt {            /**      * 加密      * @param publicKey      * @param srcBytes      * @return      * @throws NoSuchAlgorithmException      * @throws NoSuchPaddingException      * @throws InvalidKeyException      * @throws IllegalBlockSizeException      * @throws BadPaddingException      */      protected byte[] encrypt(RSAPublicKey publicKey,byte[] srcBytes) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException{          if(publicKey!=null){              //Cipher负责完成加密或解密工作，基于RSA              Cipher cipher = Cipher.getInstance("RSA");              //根据公钥，对Cipher对象进行初始化              cipher.init(Cipher.ENCRYPT_MODE, publicKey);              byte[] resultBytes = cipher.doFinal(srcBytes);              return resultBytes;          }          return null;      }            /**      * 解密       * @param privateKey      * @param srcBytes      * @return      * @throws NoSuchAlgorithmException      * @throws NoSuchPaddingException      * @throws InvalidKeyException      * @throws IllegalBlockSizeException      * @throws BadPaddingException      */      protected byte[] decrypt(RSAPrivateKey privateKey,byte[] srcBytes) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException{          if(privateKey!=null){              //Cipher负责完成加密或解密工作，基于RSA              Cipher cipher = Cipher.getInstance("RSA");              //根据公钥，对Cipher对象进行初始化              cipher.init(Cipher.DECRYPT_MODE, privateKey);              byte[] resultBytes = cipher.doFinal(srcBytes);              return resultBytes;          }          return null;      }        /**      * @param args      * @throws NoSuchAlgorithmException       * @throws BadPaddingException       * @throws IllegalBlockSizeException       * @throws NoSuchPaddingException       * @throws InvalidKeyException       */      public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException {          RSAcrypt rsa = new RSAcrypt();          String msg = "郭XX-精品相声";          //KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象          KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");          //初始化密钥对生成器，密钥大小为1024位          keyPairGen.initialize(1024);          //生成一个密钥对，保存在keyPair中          KeyPair keyPair = keyPairGen.generateKeyPair();          //得到私钥          RSAPrivateKey privateKey = (RSAPrivateKey)keyPair.getPrivate();                       //得到公钥          RSAPublicKey publicKey = (RSAPublicKey)keyPair.getPublic();                    //用公钥加密          byte[] srcBytes = msg.getBytes();          byte[] resultBytes = rsa.encrypt(publicKey, srcBytes);                    //用私钥解密          byte[] decBytes = rsa.decrypt(privateKey, resultBytes);                    System.out.println("明文是:" + msg);          System.out.println("加密后是:" + new String(resultBytes));          System.out.println("解密后是:" + new String(decBytes));      }    }