前面為大家已經總結了，基于密鑰交換的DH算法，現在就為大家再介紹一種基于因子分解的RSA算法，這種加密算法有兩種實現形式：1、公鑰加密，私鑰解密；2、私鑰加密，公鑰解密。下面就為大家分析一下實現代碼，相對于DH算法，RSA顯得有些簡單。初始化密鑰：

KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");            keyPairGenerator.initialize(512);            KeyPair keyPair = keyPairGenerator.generateKeyPair();            RSAPRivateKey rsaprivateKey = (RSAPrivateKey)keyPair.getPrivate();//私有密鑰            RSAPublicKey rsapublicKey = (RSAPublicKey)keyPair.getPublic();//公有密鑰            System.out.println("privateKey : "+Base64.encodeBase64String(rsaprivateKey.getEncoded()));            System.out.println("publicKey : "+Base64.encodeBase64String(rsapublicKey.getEncoded()));

1、私鑰加密，公鑰解密：

//私鑰加密，公鑰解密--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("私鑰加密，公鑰解密--加密:"+Base64.encodeBase64String(result));                        //私鑰加密，公鑰解密--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("私鑰加密，公鑰解密--解密:"+new String(result));

2、公鑰加密，私鑰解密：

//公鑰加密，私鑰解密---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("公鑰加密，私鑰解密---加密:"+Base64.encodeBase64String(result));                        //公鑰加密，私鑰解密---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("公鑰加密，私鑰解密---解密:"+new String(result));

　　根據輸出的結果不難發現，公鑰和私鑰并不一致，私鑰的長度要大于公鑰。

　　到今天對于信息的加密算法：Base64、對稱加密算法、消息摘要加密算法、非對稱加密算法就全部總結完畢。