信息加密之非对称加密算法RSA

时间：2023-12-21 14:54:41

　　前面为大家已经总结了，基于密钥交换的DH算法，现在就为大家再介绍一种基于因子分解的RSA算法，这种加密算法有两种实现形式：1、公钥加密，私钥解密；2、私钥加密，公钥解密。下面就为大家分析一下实现代码，相对于DH算法，RSA显得有些简单。
初始化密钥：

KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");

            keyPairGenerator.initialize(512);

            KeyPair keyPair = keyPairGenerator.generateKeyPair();

            RSAPrivateKey rsaprivateKey = (RSAPrivateKey)keyPair.getPrivate();//私有密钥

            RSAPublicKey rsapublicKey = (RSAPublicKey)keyPair.getPublic();//公有密钥

            System.out.println("privateKey : "+Base64.encodeBase64String(rsaprivateKey.getEncoded()));

            System.out.println("publicKey : "+Base64.encodeBase64String(rsapublicKey.getEncoded()));

1、私钥加密，公钥解密：

//私钥加密，公钥解密--加密

            PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaprivateKey.getEncoded());

            KeyFactory privateKeyFactory = KeyFactory.getInstance("RSA");

            PrivateKey privateKey = privateKeyFactory.generatePrivate(pkcs8EncodedKeySpec);

            Cipher privateCipher = Cipher.getInstance("RSA");

            privateCipher.init(Cipher.ENCRYPT_MODE, privateKey);

            byte[] result = privateCipher.doFinal(src.getBytes());

            System.out.println("私钥加密，公钥解密--加密:"+Base64.encodeBase64String(result));

            //私钥加密，公钥解密--解密

            X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(rsapublicKey.getEncoded());

            KeyFactory publicKeyFactory = KeyFactory.getInstance("RSA");

            PublicKey publicKey = publicKeyFactory.generatePublic(x509EncodedKeySpec);

            Cipher publicCipher = Cipher.getInstance("RSA");

            publicCipher.init(Cipher.DECRYPT_MODE, publicKey);

            result = publicCipher.doFinal(result);

            System.out.println("私钥加密，公钥解密--解密:"+new String(result));

2、公钥加密，私钥解密：

//公钥加密，私钥解密---加密

            x509EncodedKeySpec = new X509EncodedKeySpec(rsapublicKey.getEncoded());

            publicKeyFactory = KeyFactory.getInstance("RSA");

            publicKey = publicKeyFactory.generatePublic(x509EncodedKeySpec);

            publicCipher = Cipher.getInstance("RSA");

            publicCipher.init(Cipher.ENCRYPT_MODE, publicKey);

            result = publicCipher.doFinal(src.getBytes());

            System.out.println("公钥加密，私钥解密---加密:"+Base64.encodeBase64String(result));

            //公钥加密，私钥解密---解密

            pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaprivateKey.getEncoded());

            privateKeyFactory = KeyFactory.getInstance("RSA");

            privateKey = privateKeyFactory.generatePrivate(pkcs8EncodedKeySpec);

            privateCipher = Cipher.getInstance("RSA");

            privateCipher.init(Cipher.DECRYPT_MODE, privateKey);

            result = privateCipher.doFinal(result);

            System.out.println("公钥加密，私钥解密---解密:"+new String(result));

　　根据输出的结果不难发现，公钥和私钥并不一致，私钥的长度要大于公钥。

　　到今天对于信息的加密算法：Base64、对称加密算法、消息摘要加密算法、非对称加密算法就全部总结完毕。

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