JDK自带方法实现RSA数字签名

JDK 6只支持MD2withRSA, MD5withRSA, SHA1withRSA

其他的如SHA512withRSA需要第三方包支持，如BC(bouncy castle)

--20151126 更正：JDK 7已经可以支持SHA256withRSA和SHA512withRSA了

JDK的密钥长度默认仍是1024

 package jdbc.pro.lin;

 import java.security.InvalidKeyException;
 import java.security.NoSuchAlgorithmException;
 import java.security.PrivateKey;
 import java.security.PublicKey;
 import java.security.Signature;
 import java.security.SignatureException;
 import java.util.Map;

 import jdbc.pro.lin.MyRSA;

 /**
  * RSA数字签名，借用MyRSA中的算法，不再重复
  * 数字签名遵循“私钥签名，公钥验签”原则，因为私钥是个人身份认证
  * @author Kinsley
  *
  */
 public class MySignature {

     /** 数字签名算法。JDK只提供了MD2withRSA, MD5withRSA, SHA1withRSA，其他的算法需要第三方包才能支持 */
     public static final String SIGNATURE_ALGORITHM = "SHA1withRSA";

     public static final String PLAIN_TEXT = "MANUTD is the greatest club in the world";
     public static void main(String[] args)
     {
         //建立两套公私钥对
         Map<String, byte[]> keyMap1 = MyRSA.generateKeyBytes();
         PublicKey publicKey1 = MyRSA.restorePublicKey(keyMap1.get(MyRSA.PUBLIC_KEY));
         PrivateKey privateKey1 = MyRSA.restorePrivateKey(keyMap1.get(MyRSA.PRIVATE_KEY));

         Map<String, byte[]> keyMap2 = MyRSA.generateKeyBytes();
         PublicKey publicKey2 =MyRSA.restorePublicKey(keyMap2.get(MyRSA.PUBLIC_KEY));
         PrivateKey privateKey2 =MyRSA.restorePrivateKey(keyMap2.get(MyRSA.PRIVATE_KEY));

         /** 假设现在A签名后向B发送消息
          * A用B的公钥进行加密
          * 用自己A的私钥进行签名
          */
         byte[] encodedText = MyRSA.RSAEncode(publicKey2, PLAIN_TEXT.getBytes());
         byte[] signature = sign(privateKey1, PLAIN_TEXT.getBytes());

         /**
          * 现在B收到了A的消息，进行两步操作
          * 用B的私钥解密得到明文
          * 将明文和A的公钥进行验签操作
          */

         byte[] decodedText = MyRSA.RSADecode(privateKey2, encodedText).getBytes();
         System.out.println("Decoded Text: " + new String(decodedText));

         System.out.println("Signature is " + verify(publicKey1, signature, decodedText));
     }

     /**
      * 签名，三步走
      * 1. 实例化，传入算法
      * 2. 初始化，传入私钥
      * 3. 签名
      * @param key
      * @param plainText
      * @return
      */
     public static byte[] sign(PrivateKey privateKey, byte[] plainText)
     {
         try {
             //实例化
             Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);

             //初始化，传入私钥
             signature.initSign(privateKey);

             //更新
             signature.update(plainText);

             //签名
             return signature.sign();

         } catch (NoSuchAlgorithmException | InvalidKeyException | SignatureException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }

         return null;
     }

     /**
      * 验签，三步走
      * 1. 实例化，传入算法
      * 2. 初始化，传入公钥
      * 3. 验签
      * @param publicKey
      * @param signatureVerify
      * @param plainText
      * @return
      */
     public static boolean verify(PublicKey publicKey, byte[] signatureVerify, byte[] plainText )
     {
         try {
             //实例化
             Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);

             //初始化
             signature.initVerify(publicKey);

             //更新
             signature.update(plainText);

             //验签
             return signature.verify(signatureVerify);
         } catch (NoSuchAlgorithmException | InvalidKeyException | SignatureException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }

         return false;
     }
 }