Java加密與解密之非對稱加密算法

概述

非對稱加密算法與對稱加密算法的主要差別在於非對稱加密算法用於加密和解密的密鑰不相同，非對稱加密算法密鑰分為公鑰和私鑰，公鑰加密只能用私鑰解密，反之私鑰加密只能用公鑰解密。相比對稱加密算法，非對稱加密算法加/解密效率低，但安全性高，這兩種算法一般結合使用。常見非對稱加密算法有RSA、ECC、Elgamal等。

使用RSA實現加密解密

公鑰加密，私鑰解密。

package com.ss.utils;

import javax.crypto.Cipher;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;

public class RsaUtil {
    public static final String KEY_TYPE_PRIVATE_KEY = "privateKey";
    public static final String KEY_TYPE_PUBLIC_KEY = "publicKey";

    /**
     * 生成公鑰和私鑰
     *
     * @return
     * @throws NoSuchAlgorithmException
     */
    public static Map<String, String> generateKey() throws NoSuchAlgorithmException {
        Map<String, String> resultMap = new HashMap<>();
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        KeyPair keyPair = keyPairGenerator.generateKeyPair();
        Base64.Encoder encoder = Base64.getEncoder();
        resultMap.put(KEY_TYPE_PRIVATE_KEY, encoder.encodeToString(keyPair.getPrivate().getEncoded()));
        resultMap.put(KEY_TYPE_PUBLIC_KEY, encoder.encodeToString(keyPair.getPublic().getEncoded()));
        return resultMap;
    }

    /**
     * RSA加密
     * @param key
     * @param content
     * @param keyType
     * @return
     * @throws Exception
     */
    public static String rsaEncrypt(String key, String content, String keyType) throws Exception {
        return rsa(key, content.getBytes(), keyType, Cipher.ENCRYPT_MODE);
    }

    /**
     * RSA解密
     * @param key
     * @param content
     * @param keyType
     * @return
     * @throws Exception
     */
    public static String rsaDecrypt(String key, String content, String keyType) throws Exception {
        return rsa(key, Base64.getDecoder().decode(content), keyType, Cipher.DECRYPT_MODE);
    }

    private static String rsa(String key, byte[] content, String keyType, int mode) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        if (KEY_TYPE_PRIVATE_KEY.equals(keyType)) {
            cipher.init(mode, keyFactory.generatePrivate(new PKCS8EncodedKeySpec(Base64.getDecoder().decode(key))));
        } else {
            cipher.init(mode, keyFactory.generatePublic(new X509EncodedKeySpec(Base64.getDecoder().decode(key))));
        }
        byte[] bytes = cipher.doFinal(content);
        return mode == Cipher.DECRYPT_MODE ? new String(bytes) : Base64.getEncoder().encodeToString(bytes);
    }

    public static void main(String[] args) throws Exception {
        String content = "大王叫我來巡山吶";

        //生成密鑰對
        Map<String, String> keyMap = generateKey();
        System.out.println("私鑰：" + keyMap.get(KEY_TYPE_PRIVATE_KEY));
        System.out.println("公鑰：" + keyMap.get(KEY_TYPE_PUBLIC_KEY));

        //私鑰加密，公鑰解密
        String privateKeyData = rsaEncrypt(keyMap.get(KEY_TYPE_PRIVATE_KEY), content, KEY_TYPE_PRIVATE_KEY);
        System.out.println("私鑰加密：" + privateKeyData);
        System.out.println("公鑰解密：" + rsaDecrypt(keyMap.get(KEY_TYPE_PUBLIC_KEY), privateKeyData, KEY_TYPE_PUBLIC_KEY));

        //公鑰加密，私鑰解密
        String publicKeyData = rsaEncrypt(keyMap.get(KEY_TYPE_PUBLIC_KEY), content, KEY_TYPE_PUBLIC_KEY);
        System.out.println("公鑰加密：" + publicKeyData);
        System.out.println("私鑰解密：" + rsaDecrypt(keyMap.get(KEY_TYPE_PRIVATE_KEY), publicKeyData, KEY_TYPE_PRIVATE_KEY));
    }
}

輸出

私鑰：MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQDQPZnj0+/uh5jG0/rqVsXKLve7wTw2LVEwdBhm+SPrLoHYb4+6idNeF4bWgTqNRs2hfewq5cyiwXujT+eqp0g1ebSLWSUWzBsktynQMggxb8IwtnFYzmZX7BSAUudrfTre74RtKS0krYY5PCXCGR/EGbbXMVv1m2S59BrkWEI8c/iORhRAJ5/pqRW/51cIimPx9iTYx/QZC4VsCRi8ZrBaXcJhEi4Y/YzOFhfITID4ATis0Z3yw3FVybKzJo3Nexupcec5qaLBlwuDkY6E4NgQq51bjBCUB78RgXFLdaVtfBu9Vr7pRdqrh7sD//kpiicjiLJvmcLG9egXrkHRlm2TAgMBAAECggEAes75hM0mwOujBA9b+Pu3pedRHp91XRYYvZSaF5ByyG4jEXuprf8+ck05riOEXnEVMFpM/3eK2al1uviSzafeA/uEqHGoV+uDToHe3PPEtTMNuSC/c/o1jUCjTpKV/GRcZcGnvaD9CJZ1hCeetPuQKlxn4j0v2IcOPkRh36zVU0SZJKu5Ltt6iyGbpk6qqlpLnX93Ez5weWLnuolgjF34JBDQpc/zZjHwC8/avE81cJ3dUQR55l9QiwZUoMQ2eDWO1UcPAEqRssNAwEHbQJFSJmqtvg1yuSSvPIGB5ATPlTu7EoOLFMOQm3qoAxX7/FR9uU50wHivyZrRyKV4CdiLcQKBgQDuj6bh1WUQRIBU5ZOtljbs73RdYYbS1uUHubizQ3rqrNo3+TmaVu+7H3DPPI0L21YVpjXuPMUVkix+KA7HiDqULxx0yZMsdqXmggOT2QFEjGdueMFAJw09jAHnCIwuxmn3f94XAvV6N+Hfhjy31RGPQhjFGn6QQ16a3NI46CD6VwKBgQDfdorB9Wm0H6QJ8AYAQuHAiFJnXeOzN0q2407F5kx8XkAKwKaI7ybGZbiYESxFTe0AdVQlYRJbAby1iUW/OGOS+Ia5buzCo+BqrP6RxzLDYVClyXS3WFSLPKko6WIscS+uOF36mWWn34YYH/ktT8B/hUNFUD+PEctkrklONkZZJQKBgQCsn9hTbHYgKmFujV2qa5s9IhzjAZJs+MFsMLD9TuQf8opJnJdZHnWEw0B/RUKPBN0q90XpKaI3dLmrZFMlgWdaGSkPPVm4//YWcZgjIREwyCSEJO85+8gx9CDgTCgcJMlDJgzQO/zjvpI8i8deAtkc/+gqoHxa6dUIXKfmM9rBKwKBgFxIv0sUh5+8hWkZN9E5zbNOWQGZM6Tai791ph1yW1ntLnOCVgQtB41dits6FFdWtC7BRYveR89Pq1gpJaWvqueSPUktNxe2x8ImSUd4xU0Mzlp5FPt2vgt2dMGRiFqkL7W6T41jdija1az231fIHM5NAZgJaQYzqhSdKWbkYS8FAoGBAOciP4bEln64PnvuZtYnZNvt/5PHB4ssZ3S1WExyTtI7328ZKAsi3F7PjxCh7gviXfEI2t3AcVwpPaJYveL3Zg/jl2x6zNSLDW8kgNhAJE221u3pZefeidvIWwki/OXWtRqyoACteLnEb6lbM3tKdltWZOryQTiXqGdTluLEQLE0
公鑰：MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA0D2Z49Pv7oeYxtP66lbFyi73u8E8Ni1RMHQYZvkj6y6B2G+PuonTXheG1oE6jUbNoX3sKuXMosF7o0/nqqdINXm0i1klFswbJLcp0DIIMW/CMLZxWM5mV+wUgFLna3063u+EbSktJK2GOTwlwhkfxBm21zFb9ZtkufQa5FhCPHP4jkYUQCef6akVv+dXCIpj8fYk2Mf0GQuFbAkYvGawWl3CYRIuGP2MzhYXyEyA+AE4rNGd8sNxVcmysyaNzXsbqXHnOamiwZcLg5GOhODYEKudW4wQlAe/EYFxS3WlbXwbvVa+6UXaq4e7A//5KYonI4iyb5nCxvXoF65B0ZZtkwIDAQAB
私鑰加密：V9kG4o3nceI4a19t/V5431v9Ek1PiV3FZokfnRNBor/RBymwDX4rsGNHEYuyN6/sbbD56r3ij5tUpShXFlcHrzVH4IfD4ySbvNNeMs2FrZLF3zvQmwRKDPH6SJ0DEczi5N97Vfh4b2tfyLT8iX3t9LPWgEj5mB7MXiYPc56mza+ZAqDduxWWsm6Emm81uKn97wZnasg8zXlDbhRttVTWhszbDhrFqsgd2sb8ZZUZIuiGTaIg7U6Slc5x9uS3UVACXXVyMCmxiVutQtg3Z4kt80ruh7xO0hl4cWk6P2Tg0ncaIQn/5vKsO2UXr/EsCb2rchWN3ZBHTVyQ83v/EHDtQw==
公鑰解密：大王叫我來巡山吶
公鑰加密：aartOyClfEIz1JT5nghpTbXxLZEOovm+vwvg+u3Tw8t5LOF+C7Gg/uxUP8Hm5jEkN6JfBHaMWTKg0RQ2xf3CCuXcLIpYVCOUwADwd05E8guEfZBT8FIp8jghCz2j+lAIiTfGZvsK9qUdZEmwTAEjV6uP4avF6njriglGJ4KhcYXEO66tOJWe2nQ1hyYXEHS43h9F0dtlWDjF6Xr6wdmUALnhprHDwKPdT/1T8p7+M5Fz7fUC7TJulBHWCSZvhgl405PvN+iTv7VysBJKRPks1JnmMe6BxFyhxXZfNRHmUyQvTMSfWt/A5gOy8ao/SOwWv0QMSh5NbocSd/tpjn27kw==
私鑰解密：大王叫我來巡山吶

使用RSA實現數字簽名

私鑰簽名，公鑰驗證。

package com.ss.utils;

import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;

public class SignatureUtil {
    public static final String KEY_TYPE_PRIVATE_KEY = "privateKey";
    public static final String KEY_TYPE_PUBLIC_KEY = "publicKey";

    /**
     * 生成公鑰和私鑰
     *
     * @return
     * @throws NoSuchAlgorithmException
     */
    public static Map<String, String> generateKey() throws NoSuchAlgorithmException {
        Map<String, String> resultMap = new HashMap<>();
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        KeyPair keyPair = keyPairGenerator.generateKeyPair();
        Base64.Encoder encoder = Base64.getEncoder();
        resultMap.put(KEY_TYPE_PRIVATE_KEY, encoder.encodeToString(keyPair.getPrivate().getEncoded()));
        resultMap.put(KEY_TYPE_PUBLIC_KEY, encoder.encodeToString(keyPair.getPublic().getEncoded()));
        return resultMap;
    }

    /**
     * 私鑰簽名
     * @param privateKeyStr
     * @param content
     * @return
     * @throws Exception
     */
    public static String generateSignature(String privateKeyStr, String content) throws Exception {
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        Signature signature = Signature.getInstance("SHA1withRSA");
        PrivateKey privateKey = keyFactory.generatePrivate(new PKCS8EncodedKeySpec(Base64.getDecoder().decode(privateKeyStr)));
        signature.initSign(privateKey);
        signature.update(content.getBytes());
        return Base64.getEncoder().encodeToString(signature.sign());
    }

    /**
     * 公鑰驗證
     * @param publicKeyStr
     * @param content
     * @param sign
     * @return
     * @throws Exception
     */
    public static boolean verifySignature(String publicKeyStr, String content, String sign) throws Exception {
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        Signature signature = Signature.getInstance("SHA1withRSA");
        PublicKey publicKey = keyFactory.generatePublic(new X509EncodedKeySpec(Base64.getDecoder().decode(publicKeyStr)));
        signature.initVerify(publicKey);
        signature.update(content.getBytes());
        return signature.verify(Base64.getDecoder().decode(sign));
    }

    public static void main(String[] args) throws Exception {
        String content = "大王叫我來巡山吶";

        //生成密鑰對
        Map<String, String> keyMap = generateKey();

        //私鑰簽名
        String sign = generateSignature(keyMap.get(KEY_TYPE_PRIVATE_KEY), content);
        System.out.println("私鑰簽名：" + sign);

        //公鑰驗證
        boolean verifyResult = verifySignature(keyMap.get(KEY_TYPE_PUBLIC_KEY), content, sign);
        System.out.println("公鑰驗證：" + verifyResult);

        //將內容做下修改，再進行公鑰驗證
        boolean verifyResult2 = verifySignature(keyMap.get(KEY_TYPE_PUBLIC_KEY), content + "啦啦啦啦", sign);
        System.out.println("公鑰驗證：" + verifyResult2);
    }
}

輸出

私鑰簽名：XDWeOUVZhXNPl58mcmRK8ht9TAhnREc+NlnSs2b6PCJuj29ABuoXsjZeJqSspGw8hm9ckHVSTrUt8pX4BFBFzrINDRBsx3TdLp2L8nMkhjFUfo0qcyZo8ReEGFCNr0ergkq2W1Me/5W40GrQz4cJcQ4KV/QWzD8YHWcnDvKg9Q0nXJSngyhJTzUB8o/pgo/tmkA9+bWW212UD9nzEXu5aoPEcYyoo3iFWRX5o9Jgg6ZF+exmWizwZHkg4eD1zC5IN3m4yRS6GRbnZInEuDsOMp9W7HouDLUirkFZiSkyW+DVto+L6CE5eNBrWC52zxiNkVBlkyYKOatSpcrQrtnyiQ==
公鑰驗證：true
公鑰驗證：false