RSA加密解密算法工具类

1.RSA介绍

https://zh.wikipedia.org/wiki/RSA%E5%8A%A0%E5%AF%86%E6%BC%94%E7%AE%97%E6%B3%95

2.RSA加密解密工具类实现

import javax.crypto.Cipher;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.interfaces.RSAPrivateCrtKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

/**
 * author:houkai
 * Date: 2017/11/6
 * describe:     非对称加密。私钥加密 & 私钥解密 & 私钥签名
 */
public class RSAUtil {

    public static void main(String ...args){
        RSAUtil rsa = RSAUtil.create();
        String pubKey = rsa.getPublicKey();
        String priKey = rsa.getPrivateKey();

        System.out.println("公钥:"+ pubKey);
        System.out.println("私钥:"+ priKey);

        //原文
        StringBuffer res = new StringBuffer();

        res.append("123456");
        System.out.println("原文对比:"+res.toString());
        System.out.println("-----------------------");

        String enStr = rsa.encodeByPublicKey(res.toString(), pubKey);
        String deStr = rsa.decodeByPrivateKey(enStr, priKey);
        System.out.println("公钥加密:"+enStr);
        System.out.println("私钥解密:"+deStr);
        
        System.out.println("------------------------");
        enStr = rsa.encodeByPrivateKey(res.toString(), priKey);
        deStr = rsa.decodeByPublicKey(enStr, pubKey);
        System.out.println("私钥加密:"+enStr);
        System.out.println("公钥解密:"+deStr);
    }

    public static final String KEY_ALGORITHM = "RSA";
    public static final String split = " ";//分隔符
    public static final int max = 117; //加密分段长度//不可超过117

    private static RSAUtil me;
    private RSAUtil(){}//单例

    /**
     * RSA 公钥 私钥对
     * @return
     */
    public static RSAUtil create(){
        if (me==null) {
            me = new RSAUtil();
        }
        //生成公钥、私钥
        try {
            KeyPairGenerator kpg = KeyPairGenerator.getInstance(KEY_ALGORITHM);
            kpg.initialize(512);
            KeyPair kp = kpg.generateKeyPair();
            me.publicKey = (RSAPublicKey) kp.getPublic();
            me.privateKey = (RSAPrivateCrtKey) kp.getPrivate();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return me;
    }

    private RSAPublicKey publicKey;
    private RSAPrivateCrtKey privateKey;

    /**获取公钥*/
    public String getPublicKey(){
        return parseByte2HexStr(publicKey.getEncoded());
    }

    /**获取私钥*/
    public String getPrivateKey(){
        return parseByte2HexStr(privateKey.getEncoded());
    }

    /**
     * 加密-公钥
     * */
    public String encodeByPublicKey(String res,String key){
        byte[] resBytes = res.getBytes();
        byte[] keyBytes = parseHexStr2Byte(key);//先把公钥转为2进制
        StringBuffer result = new StringBuffer();//结果
        //如果超过了100个字节就分段
        if (keyBytes.length<=max) {//不超过直接返回即可
            return encodePub(resBytes, keyBytes);
        }else {
            int size = resBytes.length/max + (resBytes.length%max>0?1:0);
            for (int i = 0; i < size; i++) {
                int len = i==size-1?resBytes.length%max:max;
                byte[] bs = new byte[len];//临时数组
                System.arraycopy(resBytes, i*max, bs, 0, len);
                result.append(encodePub(bs, keyBytes));
                if(i!=size-1)result.append(split);
            }
            return result.toString();
        }
    }
    /**
     * 加密-私钥
     * */
    public String encodeByPrivateKey(String res,String key){
        byte[] resBytes = res.getBytes();
        byte[] keyBytes = parseHexStr2Byte(key);
        StringBuffer result = new StringBuffer();
        //如果超过了100个字节就分段
        if (keyBytes.length<=max) {//不超过直接返回即可
            return encodePri(resBytes, keyBytes);
        }else {
            int size = resBytes.length/max + (resBytes.length%max>0?1:0);
            for (int i = 0; i < size; i++) {
                int len = i==size-1?resBytes.length%max:max;
                byte[] bs = new byte[len];//临时数组
                System.arraycopy(resBytes, i*max, bs, 0, len);
                result.append(encodePri(bs, keyBytes));
                if(i!=size-1)result.append(split);
            }
            return result.toString();
        }
    }
    /**
     * 解密-公钥
     * */
    public String decodeByPublicKey(String res,String key){
        byte[] keyBytes = parseHexStr2Byte(key);
        //先分段
        String[] rs = res.split("\"+split);
        //分段解密
        if(rs!=null){
            int len = 0;
            //组合byte[]
            byte[] result = new byte[rs.length*max];
            for (int i = 0; i < rs.length; i++) {
                byte[] bs = decodePub(parseHexStr2Byte(rs[i]), keyBytes);
                System.arraycopy(bs, 0, result, i*max, bs.length);
                len+=bs.length;
            }
            byte[] newResult = new byte[len];
            System.arraycopy(result, 0, newResult, 0, len);
            //还原字符串
            return new String(newResult);
        }
        return null;
    }
    /**解密-私钥*/
    public String decodeByPrivateKey(String res,String key){
        byte[] keyBytes = parseHexStr2Byte(key);
        //先分段
        String[] rs = res.split("\"+split);
        //分段解密
        if(rs!=null){
            int len = 0;
            //组合byte[]
            byte[] result = new byte[rs.length*max];
            for (int i = 0; i < rs.length; i++) {
                byte[] bs = decodePri(parseHexStr2Byte(rs[i]), keyBytes);
                System.arraycopy(bs, 0, result, i*max, bs.length);
                len+=bs.length;
            }
            byte[] newResult = new byte[len];
            System.arraycopy(result, 0, newResult, 0, len);
            //还原字符串
            return new String(newResult);
        }
        return null;
    }

    /**将二进制转换成16进制 */
    private static String parseByte2HexStr(byte buf[]) {
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < buf.length; i++) {
            String hex = Integer.toHexString(buf[i] & 0xFF);
            if (hex.length() == 1) {
                hex = '0' + hex;
            }
            sb.append(hex.toUpperCase());
        }
        return sb.toString();
    }
    /**
     * 将16进制转换为二进制
     * */
    private static byte[] parseHexStr2Byte(String hexStr) {
        if (hexStr.length() < 1)
            return null;
        byte[] result = new byte[hexStr.length()/2];
        for (int i = 0;i< hexStr.length()/2; i++) {
            int high = Integer.parseInt(hexStr.substring(i*2, i*2+1), 16);
            int low = Integer.parseInt(hexStr.substring(i*2+1, i*2+2), 16);
            result[i] = (byte) (high * 16 + low);
        }
        return result;
    }

    /**加密-公钥-无分段*/
    private String encodePub(byte[] res,byte[] keyBytes){
        X509EncodedKeySpec x5 = new X509EncodedKeySpec(keyBytes);//用2进制的公钥生成x509
        try {
            KeyFactory kf = KeyFactory.getInstance(KEY_ALGORITHM);
            Key pubKey = kf.generatePublic(x5);//用KeyFactory把x509生成公钥pubKey
            Cipher cp = Cipher.getInstance(kf.getAlgorithm());//生成相应的Cipher
            cp.init(Cipher.ENCRYPT_MODE, pubKey);//给cipher初始化为加密模式，以及传入公钥pubKey
            return parseByte2HexStr(cp.doFinal(res));//以16进制的字符串返回
        } catch (Exception e) {
            System.out.println("公钥加密失败");
            e.printStackTrace();
        }
        return null;
    }
    /**加密-私钥-无分段*/
    private String encodePri(byte[] res,byte[] keyBytes){
        PKCS8EncodedKeySpec pk8 = new PKCS8EncodedKeySpec(keyBytes);
        try {
            KeyFactory kf = KeyFactory.getInstance(KEY_ALGORITHM);
            Key priKey = kf.generatePrivate(pk8);
            Cipher cp = Cipher.getInstance(kf.getAlgorithm());
            cp.init(Cipher.ENCRYPT_MODE, priKey);
            return parseByte2HexStr(cp.doFinal(res));
        } catch (Exception e) {
            System.out.println("私钥加密失败");
            e.printStackTrace();
        }
        return null;
    }
    /**解密-公钥-无分段*/
    private byte[] decodePub(byte[] res,byte[] keyBytes){
        X509EncodedKeySpec x5 = new X509EncodedKeySpec(keyBytes);
        try {
            KeyFactory kf = KeyFactory.getInstance(KEY_ALGORITHM);
            Key pubKey = kf.generatePublic(x5);
            Cipher cp = Cipher.getInstance(kf.getAlgorithm());
            cp.init(Cipher.DECRYPT_MODE, pubKey);
            return cp.doFinal(res);
        } catch (Exception e) {
            System.out.println("公钥解密失败");
            e.printStackTrace();
        }
        return null;
    }
    /**解密-私钥-无分段*/
    private byte[] decodePri(byte[] res,byte[] keyBytes){
        PKCS8EncodedKeySpec pk8 = new PKCS8EncodedKeySpec(keyBytes);
        try {
            KeyFactory kf = KeyFactory.getInstance(KEY_ALGORITHM);
            Key priKey = kf.generatePrivate(pk8);
            Cipher cp = Cipher.getInstance(kf.getAlgorithm());
            cp.init(Cipher.DECRYPT_MODE, priKey);
            return cp.doFinal(res);
        } catch (Exception e) {
            System.out.println("私钥解密失败");
            e.printStackTrace();
        }
        return null;
    } 
}

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