java实用加密算法AES和RSA

一、加密算法简介

对于机密信息，我们需要加密，目前常用的加密算法有对称加密算法与非对称加密算法。

1、对称加密算法

在对称加密中，加密方与解密方都共用同一个密钥，也就是加密与解密的密钥是一样的。

通常它的算法公开，加解密速度快。现在常用的AES算法，即advanced encrytion standard，

它的密钥长度，目前可用的是128位。

加密的原文长度不限。

2、非对称加密

非对称加密，又称公开密钥加密，它有两个密钥，公钥（public key）和私钥（private key），它们是不同的。

公钥与私钥是配对使用的，使用公钥加密时，只有对应的私钥才能解开；用私钥加密时，只有对应的公钥才能解开。

通常是接收方先生成一对密钥，即公钥和私钥，然后公钥公开，发送方用公开的公钥加密，密方传给接收方，然后接收方用私钥解密。

非对称加密没有对称加密速度快，常用的是RSA算法。

特别需要注意的是：RSA通常加密原文较小的串，串越大，keyGen.initialize(n)的n值就相应增大，加密解密速度越慢；

二、实例

添加base64的maven依赖

<dependency>    <groupId>commons-codec</groupId>    <artifactId>commons-codec</artifactId>    <version>1.10</version></dependency>

1、对称加密AES代码实例

public class AESMain {    public static void main(String[] args) throws Exception {        String source = "study hard and make progress everyday";        System.out.println("message source : "+source);        /********** 密钥生成方式一： 自动生成密钥  **************/        String keyStr = genKeyAES();  //生成密钥串        System.out.println("AES keyStr : "+keyStr);        SecretKey key = loadKeyAES(keyStr);  //根据密钥串获取密钥//        /**********  密钥生成方式二： 指定种子(或者可以说是密码)生成密钥 ***********///        String password = "123456";//        SecretKey key = genRawKeyAES(password);  //根据password获取密钥//        String keyStr = Base64.encodeBase64String(key.getEncoded());  //生成密钥串//        System.out.println("AES keyStr : "+keyStr);//        String encryptStr = encryptAES(source,key);  //AES加密        System.out.println("AES encrypt result : " + encryptStr);        String deencryptStr = deencryptAES(encryptStr,key);  //AES解密        System.out.println("AES deencrypt result : " +deencryptStr);    }    //生成密钥串    static String genKeyAES() throws Exception {        KeyGenerator keyGen = KeyGenerator.getInstance("AES");        keyGen.init(128);        SecretKey key = keyGen.generateKey();        String keyStr = Base64.encodeBase64String(key.getEncoded());        return keyStr;    }    //根据password生成密钥串    static String genKeyAES(String password) throws Exception {        SecretKey key = genRawKeyAES(password);        String keyStr = Base64.encodeBase64String(key.getEncoded());        return keyStr;    }    //根据password生成原始密钥串    static SecretKey genRawKeyAES(String password) throws Exception {        KeyGenerator keyGen = KeyGenerator.getInstance("AES");        keyGen.init(128,new SecureRandom(password.getBytes("utf8")));        SecretKey key = keyGen.generateKey();        return key;    }    //根据密钥串获取密钥    static SecretKey loadKeyAES(String keyStr) throws Exception {        SecretKey key = new SecretKeySpec(Base64.decodeBase64(keyStr), "AES");        return key;    }    //AES加密    static String encryptAES(String source, SecretKey key) throws Exception {        Cipher cipher = Cipher.getInstance("AES");        cipher.init(Cipher.ENCRYPT_MODE, key);        byte[] result = cipher.doFinal(source.getBytes("utf8"));        return Base64.encodeBase64String(result);    }    //AES解密    static String deencryptAES(String source, SecretKey key) throws Exception {        Cipher cipher = Cipher.getInstance("AES");        cipher.init(Cipher.DECRYPT_MODE, key);        byte[] resultByte = cipher.doFinal(Base64.decodeBase64(source));        String result = new String(resultByte,"utf-8");        return result;    }}

运行结果：

message source : study hard and make progress everyday
AES keyStr : evD5UdP8LK8UrfrmxGQheA==
AES encrypt result : 1z8zSWmRRFPNb6qoURgFp1c778SzaDqbErrVroDthM5eBXrQTFevAzYmRStK7EPZ
AES deencrypt result : study hard and make progress everyday

2、非对称加密算法RSA代码实例

public class RSAMain {    public static void main(String[] args) throws Exception {        String source = "study hard and make progress everyday";        System.out.println("message source : "+source);        KeyPair keyPair = getKeyPair();  //生成密钥对        String pubKeyStr = getPubKey(keyPair); //获取公钥串        System.out.println("pubKeyStr : "+pubKeyStr);        String priKeyStr = getPriKey(keyPair); //获取私钥串        System.out.println("priKeyStr : "+priKeyStr);        PublicKey pubKey = loadPubKey(pubKeyStr);//加载公钥        PrivateKey priKey = loadPriKey(priKeyStr);//加载私钥        /**************** 公钥加密 私钥解密********************/        System.out.println("\n/**************** 公钥加密 私钥解密********************/");        String encryptStr = pubEncrypt(source,pubKey);  //RSA加密        System.out.println("RSA pubKey encrypt result : " + encryptStr);        String decryptStr = priDecrypt(encryptStr,priKey);  //RSA解密        System.out.println("RSA priKey decryptStr result : " +decryptStr);        /**************** 私钥加密 公钥解密********************/        System.out.println("\n/**************** 私钥加密 公钥解密********************/");        encryptStr = priEncrypt(source,priKey);  //RSA加密        System.out.println("RSA priKey encrypt result : " + encryptStr);        decryptStr = pubDecrypt(encryptStr,pubKey);  //RSA解密        System.out.println("RSA pubKey decryptStr result : " +decryptStr);    }    //生成密钥对    static KeyPair getKeyPair() throws Exception {        KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");        keyGen.initialize(512); //可以理解为：加密后的密文长度，实际原文要小些 越大 加密解密越慢        KeyPair keyPair = keyGen.generateKeyPair();        return keyPair;    }    //获取公钥Base64字符串    static String getPubKey(KeyPair keyPair){        PublicKey key = keyPair.getPublic();        return Base64.encodeBase64String(key.getEncoded());    }    //获取私钥Base64字符串    static String getPriKey(KeyPair keyPair){        PrivateKey key = keyPair.getPrivate();        return Base64.encodeBase64String(key.getEncoded());    }    //根据公钥串获取公钥    static PublicKey loadPubKey(String keyStr) throws Exception {        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(Base64.decodeBase64(keyStr));        KeyFactory keyFactory = KeyFactory.getInstance("RSA");        PublicKey key = keyFactory.generatePublic(keySpec);        return key;    }    //根据私钥串获取私钥    static PrivateKey loadPriKey(String keyStr) throws Exception {        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(keyStr));        KeyFactory keyFactory = KeyFactory.getInstance("RSA");        PrivateKey key = keyFactory.generatePrivate(keySpec);        return key;    }    /**************** 公钥加密 私钥解密********************/    //使用公钥加密    static String pubEncrypt(String source,PublicKey key) throws Exception {        Cipher cipher = Cipher.getInstance("RSA");        cipher.init(Cipher.ENCRYPT_MODE,key);        return Base64.encodeBase64String(cipher.doFinal(source.getBytes("utf8")));    }    //使用私钥解密    static String priDecrypt(String source,PrivateKey key) throws Exception {        Cipher cipher = Cipher.getInstance("RSA");        cipher.init(Cipher.DECRYPT_MODE,key);        return new String(cipher.doFinal(Base64.decodeBase64(source)),"utf8");    }    /**************** 私钥加密 公钥解密********************/    //使用私钥加密    static String priEncrypt(String source,PrivateKey key) throws Exception {        Cipher cipher = Cipher.getInstance("RSA");        cipher.init(Cipher.ENCRYPT_MODE,key);        return Base64.encodeBase64String(cipher.doFinal(source.getBytes("utf8")));    }    //使用公钥解密    static String pubDecrypt(String source,PublicKey key) throws Exception {        Cipher cipher = Cipher.getInstance("RSA");        cipher.init(Cipher.DECRYPT_MODE,key);        return new String(cipher.doFinal(Base64.decodeBase64(source)),"utf8");    }}

运行结果：

message source : study hard and make progress everyday
pubKeyStr : M2wwDQYJKoZIhvcNAQEBBQADSwAwSAJBAItWYa39aUhRTIXEIBCSfSCp9CvXj/k9STtMv7y5OVD9ILArIf8ZwU+qepahkO40EUJ37IBS3ciiTw7CcS7U7UsCAwEAAQ==
priKeyStr : M2IBUwIBADANBgkqhkiG9w0BAQEFAASCAT0wggE5AgEAAkEAi1Zhrf1pSFFMhcQgEJJ9IKn0K9eP+T1JO0y/vLk5UP0gsCsh/xnBT6p6lqGQ7jQRQnfsgFLdyKJPDsJxLtTtSwIDAQABAkBeSJNMIl9tWeXH1hBEZntY8OeSCwkXA8tb3vEXCNap37p06hj5d2gqaK/ZkgBqVfY6keCcRqbkOROyxdfCQTjBAiEA49WvON+HhlApKXHhHglz9bmpu+LLp6NGDicTLszfGLECIQCckAMKaWcn8u1V+svGbIBHxiKI+QUBXbbo6sUZt/UkuwIgEDpcLLTfNlXnWKhf3H/X3pzG1jclQl+C0ec+morFKUECIE5CMjLnIvg2FuqOdYOWwrydzq93Akh/hqmAiMtlR7V3AiBVblFmuDimgKb8OWg+2BaWTuKZA/BG9Z8nsT2tqaNuSA==


/**************** 公钥加密 私钥解密********************/
RSA pubKey encrypt result : do1DUKBnm9J49+IhFDqPEI53tGX69kPfPbqYsPPEabm9NYTvNiEEUzjT5w1j1yQtxlz7T2n6QyHKHv0BjZOoqg==
RSA priKey decryptStr result : study hard and make progress everyday


/**************** 私钥加密 公钥解密********************/
RSA priKey encrypt result : S6bEfnsciTRNmdqe3mh9LBUsyYS5Qff6nj2xRxaiyhi2/Frw17snIZfB0rOTSnu7JjamjLZozaJ/WlwdEFcloA==
RSA pubKey decryptStr result : study hard and make progress everyday