java 非对称加密算法RSA实现详解

现在就为大家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。

来源：https://www.cnblogs.com/AndroidJotting/p/4290685.html