廖雪峯Java10加密與安全-5簽名算法-2DSA簽名算法

DSA

DSA：Digital Signature Algorithm，使用EIGamal數字簽名算法，和RSA數字簽名相比，DSA更快。 DSA只能配合SHA使用：

• SHA1withDSA
• SHA256withDSA
• SHA512withDSA

代碼演示：

package com.testList;

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

public class SecDSASignature {
    PrivateKey sk;
    PublicKey pk;
    public SecDSASignature() throws GeneralSecurityException{
        //generate key pair
        KeyPairGenerator kpGen = KeyPairGenerator.getInstance("DSA");
        kpGen.initialize(1024);
        KeyPair kp = kpGen.generateKeyPair();
        this.sk = kp.getPrivate();
        this.pk = kp.getPublic();
    }
    public SecDSASignature(byte[] pk,byte[] sk) throws GeneralSecurityException{
        //create from bytes
        KeyFactory kf = KeyFactory.getInstance("DSA");
        X509EncodedKeySpec pkSpec = new X509EncodedKeySpec(pk);
        this.pk = kf.generatePublic(pkSpec);
        PKCS8EncodedKeySpec skSpec = new PKCS8EncodedKeySpec(sk);
        this.sk = kf.generatePrivate(skSpec);
    }
    public byte[] getPrivateKey(){
        return this.sk.getEncoded();
    }
    public byte[] getPublicKey(){
        return this.pk.getEncoded();
    }
    public byte[] sign(byte[] message) throws GeneralSecurityException{
        //sign by sk;
        Signature signature = Signature.getInstance("SHA1withDSA");
        signature.initSign(this.sk);
        signature.update(message);
        return signature.sign();
    }
    public boolean verify(byte[] message,byte[] sign) throws GeneralSecurityException{
        //verify by pk
        Signature signature = Signature.getInstance("SHA1withDSA");
        signature.initVerify(this.pk);
        signature.update(message);
        return signature.verify(sign);
    }
    public static void main(String[] args) throws Exception{
        byte[] message = "Hello,使用SHA1withDSA算法進行數字簽名".getBytes("utf-8");
        SecDSASignature rasa = new SecDSASignature();
        byte[] sign = rasa.sign(message);
        System.out.println("sign:"+ Base64.getEncoder().encodeToString(sign));
        boolean verified = rasa.verify(message,sign);
        System.out.println("verify:"+verified);
        message[0] = 100;
        boolean verified2 = rasa.verify(message,sign);
        System.out.println("verified2:"+verified2);
    }
}

<img src="https://img2018.cnblogs.com/blog/1418970/201905/1418970-20190522214956227-242656727.png" width="500" />

總結：

• DSA是另外一種簽名算法
• 其餘數字簽名算法 * ECDSA：Elliptic Curve Digital Signature Algorithm（Bouncy Castle）