java 非对称加密算法RSA实现详解

时间：2021-03-17 09:39:29|栏目：JAVA代码|点击：次

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。

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