java后台实现 RSA加密

RSA算法

RSA加密算法是一种非对称加密算法。在公开密钥加密和电子商业中RSA被广泛使用。RSA是1977年由罗纳德·李维斯特（Ron Rivest）、阿迪·萨莫尔（Adi Shamir）和伦纳德·阿德曼（Leonard Adleman）一起提出的。当时他们三人都在麻省理工学院工作。RSA就是他们三人姓氏开头字母拼在一起组成的。

在公开密钥密码体制中，加密密钥（即公开密钥）PK是公开信息，而解密密钥（即秘密密钥）SK是需要保密的。加密算法E和解密算法D也都是公开的。虽然解密密钥SK是由公开密钥PK决定的，但却不能根据PK计算出SK。

下面是java后台实现代码：

1.引入jar包

<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcprov-jdk16</artifactId>
    <version>1.46</version>
</dependency>

2.实现基于rsa方式操作工具类：

RSAUtils：

package com.yg.sixpre.utils;

import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.RSAPrivateKeySpec;
import java.security.spec.RSAPublicKeySpec;
import java.util.HashMap;

import javax.crypto.Cipher;

/**
 * @ClassName: RSAUtils
 * @Description: 公钥、密钥生成和校验
 * @author p7
 * @date 2018年7月12日
 **/
public class RSAUtils {
    /**
     * 生成公钥和私钥
     *
     * @throws NoSuchAlgorithmException
     *
     */
    public static HashMap<String, Object> getKeys() throws NoSuchAlgorithmException {
        HashMap<String, Object> map = new HashMap<String, Object>();
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA",
                new org.bouncycastle.jce.provider.BouncyCastleProvider());
        keyPairGen.initialize(1024);
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        map.put("public", publicKey);
        map.put("private", privateKey);
        return map;
    }

    /**
     * 使用模和指数生成RSA公钥
     *
     *
     * @param modulus
     *            模
     * @param exponent
     *            指数
     * @return
     */
    public static RSAPublicKey getPublicKey(String modulus, String exponent) {
        try {
            BigInteger b1 = new BigInteger(modulus);
            BigInteger b2 = new BigInteger(exponent);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA",
                    new org.bouncycastle.jce.provider.BouncyCastleProvider());
            RSAPublicKeySpec keySpec = new RSAPublicKeySpec(b1, b2);
            return (RSAPublicKey) keyFactory.generatePublic(keySpec);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 使用模和指数生成RSA私钥
     *
     * /None/NoPadding
     *
     * @param modulus
     *            模
     * @param exponent
     *            指数
     * @return
     */
    public static RSAPrivateKey getPrivateKey(String modulus, String exponent) {
        try {
            BigInteger b1 = new BigInteger(modulus);
            BigInteger b2 = new BigInteger(exponent);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA",
                    new org.bouncycastle.jce.provider.BouncyCastleProvider());
            RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(b1, b2);
            return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 公钥加密
     *
     * @param data
     * @param publicKey
     * @return
     * @throws Exception
     */
    public static String encryptByPublicKey(String data, RSAPublicKey publicKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        // 模长
        int key_len = publicKey.getModulus().bitLength() / 8;
        // 加密数据长度 <= 模长-11
        String[] datas = splitString(data, key_len - 11);
        String mi = "";
        // 如果明文长度大于模长-11则要分组加密
        for (String s : datas) {
            mi += bcd2Str(cipher.doFinal(s.getBytes()));
        }
        return mi;
    }

    /**
     * 私钥解密
     *
     * @param data
     * @param privateKey
     * @return
     * @throws Exception
     */
    public static String decryptByPrivateKey(String data, RSAPrivateKey privateKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        // 模长
        int key_len = privateKey.getModulus().bitLength() / 8;
        byte[] bytes = data.getBytes();
        byte[] bcd = ASCII_To_BCD(bytes, bytes.length);
        // System.err.println(bcd.length);
        // 如果密文长度大于模长则要分组解密
        String ming = "";
        byte[][] arrays = splitArray(bcd, key_len);
        for (byte[] arr : arrays) {
            ming += new String(cipher.doFinal(arr));
        }
        return ming;
    }

    /**
     * ASCII码转BCD码
     *
     */
    public static byte[] ASCII_To_BCD(byte[] ascii, int asc_len) {
        byte[] bcd = new byte[asc_len / 2];
        int j = 0;
        for (int i = 0; i < (asc_len + 1) / 2; i++) {
            bcd[i] = asc_to_bcd(ascii[j++]);
            bcd[i] = (byte) (((j >= asc_len) ? 0x00 : asc_to_bcd(ascii[j++])) + (bcd[i] << 4));
        }
        return bcd;
    }

    public static byte asc_to_bcd(byte asc) {
        byte bcd;

        if ((asc >= '0') && (asc <= '9'))
            bcd = (byte) (asc - '0');
        else if ((asc >= 'A') && (asc <= 'F'))
            bcd = (byte) (asc - 'A' + 10);
        else if ((asc >= 'a') && (asc <= 'f'))
            bcd = (byte) (asc - 'a' + 10);
        else
            bcd = (byte) (asc - 48);
        return bcd;
    }

    /**
     * BCD转字符串
     */
    public static String bcd2Str(byte[] bytes) {
        char temp[] = new char[bytes.length * 2], val;

        for (int i = 0; i < bytes.length; i++) {
            val = (char) (((bytes[i] & 0xf0) >> 4) & 0x0f);
            temp[i * 2] = (char) (val > 9 ? val + 'A' - 10 : val + '0');

            val = (char) (bytes[i] & 0x0f);
            temp[i * 2 + 1] = (char) (val > 9 ? val + 'A' - 10 : val + '0');
        }
        return new String(temp);
    }

    /**
     * 拆分字符串
     */
    public static String[] splitString(String string, int len) {
        int x = string.length() / len;
        int y = string.length() % len;
        int z = 0;
        if (y != 0) {
            z = 1;
        }
        String[] strings = new String[x + z];
        String str = "";
        for (int i = 0; i < x + z; i++) {
            if (i == x + z - 1 && y != 0) {
                str = string.substring(i * len, i * len + y);
            } else {
                str = string.substring(i * len, i * len + len);
            }
            strings[i] = str;
        }
        return strings;
    }

    /**
     * 拆分数组
     */
    public static byte[][] splitArray(byte[] data, int len) {
        int x = data.length / len;
        int y = data.length % len;
        int z = 0;
        if (y != 0) {
            z = 1;
        }
        byte[][] arrays = new byte[x + z][];
        byte[] arr;
        for (int i = 0; i < x + z; i++) {
            arr = new byte[len];
            if (i == x + z - 1 && y != 0) {
                System.arraycopy(data, i * len, arr, 0, y);
            } else {
                System.arraycopy(data, i * len, arr, 0, len);
            }
            arrays[i] = arr;
        }
        return arrays;
    }

    public static void main(String[] args) throws Exception {
        HashMap<String, Object> map = getKeys();
        // 生成公钥和私钥
        RSAPublicKey publicKey = (RSAPublicKey) map.get("public");
        RSAPrivateKey privateKey = (RSAPrivateKey) map.get("private");

        // 模
        String modulus = publicKey.getModulus().toString();
        System.out.println("pubkey modulus=" + modulus);
        // 公钥指数
        String public_exponent = publicKey.getPublicExponent().toString();
        System.out.println("pubkey exponent=" + public_exponent);
        // 私钥指数
        String private_exponent = privateKey.getPrivateExponent().toString();
        System.out.println("private exponent=" + private_exponent);
        // 明文
        String ming = "yangzhen";
        // 使用模和指数生成公钥和私钥
        RSAPublicKey pubKey = RSAUtils.getPublicKey(modulus, public_exponent);
        RSAPrivateKey priKey = RSAUtils.getPrivateKey(modulus, private_exponent);
        // 加密后的密文
        String mi = RSAUtils.encryptByPublicKey(ming, pubKey);
        System.err.println("mi=" + mi);
        // 解密后的明文
        String ming2 = RSAUtils.decryptByPrivateKey(mi, priKey);
        System.err.println("ming2=" + ming2);
    }
}

3.调用获取公钥和私钥的方法：

/**
 * @Title: generateRSAKey
 * @Description: 生成公钥和私钥，我这里是要求前端传递过来登录名（不能重复），目的是以这个为key值将生成的私钥放到redis中
 * 方便在登录的时候和前端传递过来的公钥进行对比解密
 * @param username
 */
public Result generateRSAKey(@PathVariable String username) {

    try {
        // 获取公钥和私钥
        HashMap<String, Object> keys = RSAUtils.getKeys();
        RSAPublicKey publicKey = (RSAPublicKey) keys.get("public");
        RSAPrivateKey privateKey = (RSAPrivateKey) keys.get("private");
        // 保存私钥到 redis，也可以保存到数据库
        redisService.setForHash("RSAKEY",username,privateKey,null);
        // 将公钥传到前端
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("publicKey", publicKey);

        return ResultGenerator.genSuccessResult(ResultCode.SUCCESS.getCode(),ResultCode.SUCCESS.getMsg(),map);
    } catch (Exception e) {
        return ResultGenerator.genSuccessResult(ResultCode.RSAKEY_ERROR.getCode(),ResultCode.RSAKEY_ERROR.getMsg(),null);
    }
}

4.解密代码片段：

//获取缓存在redis中的私钥
Object object = redisService.get(username);
try {
    // 解密，password属性是前端根据公钥加密的字符串
    String decryptByPrivateKey = RSAUtils.decryptByPrivateKey(password, (RSAPrivateKey) object);
    if (decryptByPrivateKey != null ) {
        password = decryptByPrivateKey;
    } else {
        password = null;
    }
    //解密成功后根据密码进行登录操作，一下代码不写了
} catch (Exception e) {
    return  "解密出错了";
} 

前端实现rsa加密下节更新