Java实现RSA密钥对并在加解密、加签验签中应用的实例

一.项目结构

二.代码具体实现

1.密钥对生成的两种方式：一种生成公钥私文件，一种生成公钥私串

KeyPairGenUtil.java

package com.wangjinxiang.genkey.util;

import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import sun.misc.BASE64Encoder;

public class KeyPairGenUtil {

    /** 指定加密算法为RSA */
    private static final String ALGORITHM = "RSA";
    /** 密钥长度，用来初始化 */
    private static final int KEYSIZE = 1024;
    /** 指定公钥存放文件 */
    private static String PUBLIC_KEY_FILE = "PublicKey";
    /** 指定私钥存放文件 */
    private static String PRIVATE_KEY_FILE = "PrivateKey";

    public static void main(String[] args) throws Exception {
        //generateKeyPair();
        genKeyPair();
    }

    /**
    * 生成密钥对文件
    * @throws Exception
    */
    private static void generateKeyPair() throws Exception {

        //     /** RSA算法要求有一个可信任的随机数源 */
        //     SecureRandom secureRandom = new SecureRandom();
        /** 为RSA算法创建一个KeyPairGenerator对象 */
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);

        /** 利用上面的随机数据源初始化这个KeyPairGenerator对象 */
        //     keyPairGenerator.initialize(KEYSIZE, secureRandom);
        keyPairGenerator.initialize(KEYSIZE);

        /** 生成密匙对 */
        KeyPair keyPair = keyPairGenerator.generateKeyPair();

        /** 得到公钥 */
        Key publicKey = keyPair.getPublic();

        /** 得到私钥 */
        Key privateKey = keyPair.getPrivate();

        ObjectOutputStream oos1 = null;
        ObjectOutputStream oos2 = null;
        try {
            /** 用对象流将生成的密钥写入文件 */
            oos1 = new ObjectOutputStream(new FileOutputStream(PUBLIC_KEY_FILE));
            oos2 = new ObjectOutputStream(new FileOutputStream(PRIVATE_KEY_FILE));
            oos1.writeObject(publicKey);
            oos2.writeObject(privateKey);
        } catch (Exception e) {
            throw e;
        } finally {
            /** 清空缓存，关闭文件输出流 */
            oos1.close();
            oos2.close();
        }
    }

    /**
     * 生成密钥对
     * @throws NoSuchAlgorithmException
     */
    private static void genKeyPair() throws NoSuchAlgorithmException {
        
        /** RSA算法要求有一个可信任的随机数源 */
        SecureRandom secureRandom = new SecureRandom();
        
        /** 为RSA算法创建一个KeyPairGenerator对象 */
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);

        /** 利用上面的随机数据源初始化这个KeyPairGenerator对象 */
        keyPairGenerator.initialize(KEYSIZE, secureRandom);
        //keyPairGenerator.initialize(KEYSIZE);

        /** 生成密匙对 */
        KeyPair keyPair = keyPairGenerator.generateKeyPair();

        /** 得到公钥 */
        Key publicKey = keyPair.getPublic();

        /** 得到私钥 */
        Key privateKey = keyPair.getPrivate();

        byte[] publicKeyBytes = publicKey.getEncoded();
        byte[] privateKeyBytes = privateKey.getEncoded();

        String publicKeyBase64 = new BASE64Encoder().encode(publicKeyBytes);
        String privateKeyBase64 = new BASE64Encoder().encode(privateKeyBytes);

        System.out.println("publicKeyBase64.length():" + publicKeyBase64.length());
        System.out.println("publicKeyBase64:" + publicKeyBase64);

        System.out.println("privateKeyBase64.length():" + privateKeyBase64.length());
        System.out.println("privateKeyBase64:" + privateKeyBase64);
    }
}

2.将密钥串生成方式的密钥对在常量类里定义，以便后面的应用使用

Constants.java

package com.wangjinxiang.constant;

public class Constants {

  //#priKeyText
  public final static String priKeyText = "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";
  
  //#pubKeyText
  public final static String pubKeyText = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCYO23qMcvv0gpGs97rfmxITjjz5m/sjZ4JgYvPBs+JHwD/SCv7TJCEKVm4aXTEPTXRkN7LgUjQTnEGGS1JBY4zyqpnmJcfpNxWpdgAyE/4poMJ8rcZvqm14DOjNH+69mwpIdJkySHuzUCzQtMJ8GG2owNc9frTOpZozlcUWbGWfQIDAQAB";
}

DigestUtil.java

package com.wangjinxiang.util;

public class DigestUtil {

    /**
     * 字节转为十六进制字符串
     * @param字节
     * @return 十六进制字符串
     */
    public static String byte2hex(byte[] b) {
        String hs = "";
        String stmp = "";
        for (int n = 0; b != null && n < b.length; n++) {
            stmp = (java.lang.Integer.toHexString(b[n] & 0XFF));
            if (stmp.length() == 1)
                hs = hs + "0" + stmp;
            else
                hs = hs + stmp;
        }
        return hs;
    }

    /**
     * 十六进制字符转为字节
     * @param 十六进制字符
     * @return  字节
     */
    public static byte[] hex2byte(byte[] b) {
        if ((b.length % 2) != 0)
            throw new IllegalArgumentException("byte length is not correct");
        byte[] b2 = new byte[b.length / 2];
        for (int n = 0; n < b.length; n += 2) {
            String item = new String(b, n, 2);
            b2[n / 2] = (byte) Integer.parseInt(item, 16);
        }
        return b2;
    }

    /**
     * 字符串转换成十六进制值
     * @param bin String 我们看到的要转换成十六进制的字符串
     * @return
    */
    public static String bin2hex(String bin) {
        char[] digital = "0123456789ABCDEF".toCharArray();
        StringBuffer sb = new StringBuffer("");
        byte[] bs = bin.getBytes();
        int bit;
        for (int i = 0; i < bs.length; i++) {
            bit = (bs[i] & 0x0f0) >> 4;
            sb.append(digital[bit]);
            bit = bs[i] & 0x0f;
            sb.append(digital[bit]);
        }
        return sb.toString();
    }
}

3.加解密应用实例RSAUtil.java

说明：加解密是用公钥加密，用私钥解密

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package com.wangjinxiang.util;

import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.spec.PKCS8EncodedKeySpec;
import javax.crypto.Cipher;
import org.apache.commons.codec.binary.Base64;
import com.wangjinxiang.constant.Constants;
import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

public class RSAUtil {
    
    /** 指定加密算法为RSA */
    private static final String ALGORITHM = "RSA";

    public static void main(String[] args) throws Exception {
        
        String source = "深圳,您好!";// 要加密的字符串
        System.out.println("准备用公钥加密的字符串为：" + source);
        
        String cryptograph = encrypt(source);// 生成的密文
        System.out.print("用公钥加密后的结果为:" + cryptograph);
        System.out.println();
       
        String target = decrypt(cryptograph);// 解密密文
        System.out.println("用私钥解密后的字符串为：" + target);
        System.out.println();   
    }
    
    /**
     * 加密方法
     * @param source 源数据
     * @return
     * @throws Exception
     */
    public static String encrypt(String source) throws Exception {
        
        java.security.spec.X509EncodedKeySpec x509KeySpec = new java.security.spec.X509EncodedKeySpec(Base64.decodeBase64(Constants.pubKeyText));
        // RSA算法
        java.security.KeyFactory keyFactory = java.security.KeyFactory.getInstance("RSA");
        // 取公钥匙对象
        java.security.PublicKey publicKey = keyFactory.generatePublic(x509KeySpec);
        // 得到Cipher对象来实现对源数据的RSA加密
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        byte[] b = source.getBytes();
        /** 执行加密操作 */
        byte[] b1 = cipher.doFinal(b);
        BASE64Encoder encoder = new BASE64Encoder();
        return encoder.encode(b1);
    }

    /**
     * 解密算法
     * @param cryptograph    密文
     * @return
     * @throws Exception
     */
    public static String decrypt(String cryptograph) throws Exception {
        
        PKCS8EncodedKeySpec priPKCS8 = new PKCS8EncodedKeySpec(Base64.decodeBase64(Constants.priKeyText));
        KeyFactory keyf = KeyFactory.getInstance("RSA");
        PrivateKey privateKey = keyf.generatePrivate(priPKCS8);

        /** 得到Cipher对象对已用公钥加密的数据进行RSA解密 */
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        BASE64Decoder decoder = new BASE64Decoder();
        byte[] b1 = decoder.decodeBuffer(cryptograph);

        /** 执行解密操作 */
        byte[] b = cipher.doFinal(b1);
        return new String(b);
    }
}

运行结果：

准备用公钥加密的字符串为：深圳,您好!
用公钥加密后的结果为:Q5bZjBlIIPII04NOCIwYDPYBGNSC5Hv7XKc8TlkCRbZyAK4M4nm9uYcEded0Nbj7HeLXNZY8XrQD
l2+FsYjfL0DlioCoJQm7bnwlVwYmdNMXOB3bfepywpeFRDSNswJxueLqVtmIKcbuCuXBvdIqrfDq
PVbCVfI59/GhqAcqM6U=
用私钥解密后的字符串为：深圳,您好!

4.加签验签实例SignUtil.java

说明：加签是用私钥，验签是用公钥

package com.wangjinxiang.util;

import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.spec.PKCS8EncodedKeySpec;
import org.apache.commons.codec.binary.Base64;
import com.wangjinxiang.constant.Constants;

public class SignUtil {
    
    private final static String CHARACTER_ENCODING_UTF_8 = "UTF-8";
    
    public static void main(String[] args) {
        
        String signString = "深圳,您好!";
        try {
            // 加签
            String localSignature = SignUtil.sign(Constants.priKeyText.getBytes(CHARACTER_ENCODING_UTF_8), signString);
            System.out.println(localSignature);
            //验签
            boolean verifyResult = SignUtil.verify(Constants.pubKeyText.getBytes(CHARACTER_ENCODING_UTF_8), signString, localSignature);
            System.out.println("verifyResult:" + verifyResult);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    /**
     * RSA私钥加签
     * @param priKeyText经过base64处理后的私钥
     * @param plainText明文内容
     * @return 十六进制的签名字符串
     * @throws Exception 
     */
    public static String sign(byte[] priKeyText, String plainText) throws Exception {
        try {
            PKCS8EncodedKeySpec priPKCS8 = new PKCS8EncodedKeySpec(Base64.decodeBase64(priKeyText));
            KeyFactory keyf = KeyFactory.getInstance("RSA");
            PrivateKey prikey = keyf.generatePrivate(priPKCS8);

            // 用私钥对信息生成数字签名
            java.security.Signature signet = java.security.Signature.getInstance("SHA256withRSA");
            signet.initSign(prikey);
            signet.update(plainText.getBytes("UTF-8"));
            return DigestUtil.byte2hex(signet.sign());
        } catch (Exception e) {
            throw e; 
        }
    }
    
    /**
     * 公钥验签
     * @param pubKeyText经过base64处理后的公钥
     * @param plainText明文内容
     * @param signText十六进制的签名字符串
     * @return 验签结果 true验证一致 false验证不一致
     */
    public static boolean verify(byte[] pubKeyText, String plainText, String signText) {
        try {
            // 解密由base64编码的公钥,并构造X509EncodedKeySpec对象
            java.security.spec.X509EncodedKeySpec bobPubKeySpec = new java.security.spec.X509EncodedKeySpec(
                    Base64.decodeBase64(pubKeyText));
            // RSA算法
            java.security.KeyFactory keyFactory = java.security.KeyFactory.getInstance("RSA");
            // 取公钥匙对象
            java.security.PublicKey pubKey = keyFactory.generatePublic(bobPubKeySpec);
            // 十六进制数字签名转为字节
            byte[] signed = DigestUtil.hex2byte(signText.getBytes("UTF-8"));
            java.security.Signature signatureChecker = java.security.Signature.getInstance("SHA256withRSA");
            signatureChecker.initVerify(pubKey);
            signatureChecker.update(plainText.getBytes("UTF-8"));
            // 验证签名是否正常
            return signatureChecker.verify(signed);
        } catch (Throwable e) {
            return false;
        }
    }
}

运行结果：

7ef0cd04a3dc41ae1396a90a3d8a8b799c68c65202361823dd3a71a05fc2bf57c09ebe2074ba49008cf58288297267d770137ee267c6c296a784c7d50c607c73e1d78799c7de5dadf183f011d604df7270ce5616e465ddc93a95df9095249702fc265e97ed7ab2adf4535d13237040653d7f000a3080a0c4f11f84bbe48849e7
verifyResult:true

5.从生成的密钥对文件中读取公私钥加解密实例RSAUtil02.java

package com.wangjinxiang.util2;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.security.Key;

import javax.crypto.Cipher;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

public class RSAUtil02 {
    
    /** 指定加密算法为RSA */
    private static final String ALGORITHM = "RSA";
    /** 指定公钥存放文件 */
    private static String PUBLIC_KEY_FILE = "PublicKey";
    /** 指定私钥存放文件 */
    private static String PRIVATE_KEY_FILE = "PrivateKey";

    public static void main(String[] args) throws Exception {
        
        String source = "深圳,您好!";// 要加密的字符串
        System.out.println("准备用公钥加密的字符串为：" + source);
        
        String cryptograph = encrypt(source);// 生成的密文
        System.out.print("用公钥加密后的结果为:" + cryptograph);
        System.out.println();
       
        String target = decrypt(cryptograph);// 解密密文
        System.out.println("用私钥解密后的字符串为：" + target);
        System.out.println();   
    }
    
    /**
     * 加密方法
     * @param source 源数据
     * @return
     * @throws Exception
     */
    public static String encrypt(String source) throws Exception {
        
        Key publicKey = getKey(PUBLIC_KEY_FILE);

        /** 得到Cipher对象来实现对源数据的RSA加密 */
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        byte[] b = source.getBytes();
        /** 执行加密操作 */
        byte[] b1 = cipher.doFinal(b);
        BASE64Encoder encoder = new BASE64Encoder();
        return encoder.encode(b1);
    }

    /**
     * 解密算法
     * @param cryptograph    密文
     * @return
     * @throws Exception
     */
    public static String decrypt(String cryptograph) throws Exception {
        
        Key privateKey = getKey(PRIVATE_KEY_FILE);

        /** 得到Cipher对象对已用公钥加密的数据进行RSA解密 */
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        BASE64Decoder decoder = new BASE64Decoder();
        byte[] b1 = decoder.decodeBuffer(cryptograph);

        /** 执行解密操作 */
        byte[] b = cipher.doFinal(b1);
        return new String(b);
    }
    
    private static Key getKey(String fileName) throws Exception, IOException {
        Key key;
        ObjectInputStream ois = null;
        try {
            /** 将文件中的私钥对象读出 */
            ois = new ObjectInputStream(new FileInputStream(fileName));
            key = (Key) ois.readObject();
        } catch (Exception e) {
            throw e;
        } finally {
            ois.close();
        }
        return key;
    }
}

运行结果：

准备用公钥加密的字符串为：深圳,您好!
用公钥加密后的结果为:Ep2Y6EstlUWQnmVxsZ0/NIV1NFIPAlg8rJguRdQB+2uBD+/sunrPiVoCm3zbuj317CNG5hwijNBf
qKETmd7HoftpnHxzYwn+lWqlVdUHIO+ZrFn2OB6omlA/aFHCZzIHtKDU72cNuiBiwONxCXyaWq4Z
scDfvzbz3//UYOhlDs4=
用私钥解密后的字符串为：深圳,您好!