digitalsignature2example.java

这是一个文本加密、解密系统

package example;

/**
*DigitalSignature2Example.java
*Copyright 2005-2-16
*/
import java.security.Signature;
import java.security.KeyPairGenerator;
import java.security.KeyPair;
import java.security.SignatureException;

/**
*数字签名，使用RSA私钥对对消息摘要签名，然后使用公?验证 测试
*/
public class DigitalSignature2Example{
public static void main(String[] args) throws Exception
{
    if(args.length!=1){
        System.err.println("Usage:java DigitalSignature2Example ");
        System.exit(1);
    }

    byte[] plainText=args[0].getBytes("UTF8");
    //形成RSA公钥对
    System.out.println("\nStart generating RSA key");
    KeyPairGenerator keyGen=KeyPairGenerator.getInstance("RSA");
    keyGen.initialize(1024);

    KeyPair key=keyGen.generateKeyPair();
    System.out.println("Finish generating RSA key");
    //使用私?签名
    Signature sig=Signature.getInstance("SHA1WithRSA");
    sig.initSign(key.getPrivate());
    sig.update(plainText);
    byte[] signature=sig.sign();
    System.out.println(sig.getProvider().getInfo());
    System.out.println("\nSignature:");
    System.out.println(new String(signature,"UTF8"));
    

    //使用公?验证
    System.out.println("\nStart signature verification");
    sig.initVerify(key.getPublic());
    sig.update(plainText);
    try{
        if(sig.verify(signature))
            System.out.println("Signature verified");
        else System.out.println("Signature failed");
    }
    catch(SignatureException e){
        System.out.println("Signature failed");
    }
  }
}