通过Java JDK实现数字签名RSA算法

​使用到了commons-codec  jar包 ！！！​

package com.hern.rsa;

import org.apache.commons.codec.binary.Hex;

import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

public class RSACodec {

    private static String string = "hern";

    public static void main(String[] args) throws InvalidKeySpecException, NoSuchAlgorithmException, InvalidKeyException, SignatureException {
        jdkRSA();
    }

    public static void jdkRSA() throws NoSuchAlgorithmException, InvalidKeySpecException, InvalidKeyException, SignatureException {
        //初始化秘钥
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        keyPairGenerator.initialize(512);
        KeyPair keyPair = keyPairGenerator.generateKeyPair();
        RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic();
        RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate();

        //执行秘钥
        PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
        Signature signature = Signature.getInstance("MD5withRSA");
        signature.initSign(privateKey);
        signature.update(string.getBytes());
        byte[] result = signature.sign();
        System.out.println(Hex.encodeHexString(result));

        //验证签名
        X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded());
        keyFactory = KeyFactory.getInstance("RSA");
        PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
        signature = Signature.getInstance("MD5withRSA");
        signature.initVerify(publicKey);
        signature.update(string.getBytes());
        boolean bool = signature.verify(result);
        System.out.println("jdk rsa verify : " + bool);
    }
}