RSA 算法工具類(純JDK，無引入jar)

 下面是RSA 生成公私鑰 加解密 加簽驗籤的功能類

開放平臺簽名算法名稱	標準簽名算法名稱	備註
RSA2	SHA256WithRSA	強制要求 RSA 密鑰的長度至少爲 2048
RSA	SHA1WithRSA	對 RSA 密鑰的長度不限制，推薦使用 2048 位以上

由於計算能力的飛速發展，從安全性角度考慮，儘可能考慮RSA2,該算法在摘要算法上比 SHA1WithRSA 有更強的安全能力。

目前 SHA1WithRSA 的簽名算法很多地方也提供支持，但爲了您的應用安全，強烈建議使用 SHA256WithRSA 的簽名算法。

keySize長度推薦 2048位

工具類 使用的 全部是 jdk自帶jar 不需要引入其他包，附帶基礎測試，工具類使用的是RSA2 keysize 默認 2048，標準算法名稱爲

SHA256WithRSA 

package utils;

import javax.crypto.Cipher;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;

/**
 * @Author: 四靈
 * @Description: RSA 非對稱 加密解密 加簽驗籤工具
 * @Date: Created in 15:01 2016/4/9
 */
@SuppressWarnings("all")
public class RSAUtils {
    //取值 SHA256WithRSA  或者 SHA1WithRSA
    //RSA 對應 SHA1WithRSA
    //RSA2 對應 SHA256WithRSA  至少2048 位以上
    public static final String SHA_WITH_RSA_ALGORITHM = "SHA256WithRSA";

    public static final String MD5_WITH_RSA = "MD5WithRSA";

    public static final int KEY_SIZE_2048 = 2048;

    public static final int KEY_SIZE_1024 = 1024;

    public static final String  ALGORITHM = "RSA";

    public static final String  CHARSET = "UTF-8";


    /**
     * SHAWithRSA簽名
     */
    public static String sign(String in,String pivateKey,String algorithm) throws Exception{
        PKCS8EncodedKeySpec priPKCS8 = new PKCS8EncodedKeySpec(Base64.getDecoder().decode(pivateKey));
        KeyFactory keyf = KeyFactory.getInstance(ALGORITHM);
        PrivateKey priKey = keyf.generatePrivate(priPKCS8);
        Signature signa = Signature.getInstance(algorithm!=null?algorithm:SHA_WITH_RSA_ALGORITHM);
        signa.initSign(priKey);
        signa.update(in.getBytes());
        byte[] signdata = signa.sign();
        return Base64.getEncoder().encodeToString(signdata);
    }

    /**
     * SHAWithRSA簽名
     * 默認 SHAWithRSA簽名
     */
    public static String sign(String in,String pivateKey) throws Exception{
        return sign(in,pivateKey,null);
    }

    /**
     * SHAWithRSA驗籤
     * 默認SHAWithRSA驗籤
     */
    public static boolean isValid(String in,String signData,String publicKey,String algorithm) throws Exception{
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
        byte[] encodedKey = Base64.getDecoder().decode(publicKey);
        PublicKey pubKey = keyFactory.generatePublic(new X509EncodedKeySpec(encodedKey));
		Signature signa = Signature.getInstance(algorithm!=null?algorithm:SHA_WITH_RSA_ALGORITHM);
        signa.initVerify(pubKey);
        signa.update(in.getBytes());
        byte[] sign_byte = Base64.getDecoder().decode(signData);
        boolean flag = signa.verify(sign_byte);
        return flag;
    }

    /**
     *  SHAWithRSA驗籤
     */
    public static boolean isValid(String in,String signData,String publicKey) throws Exception{
        return isValid(in,signData,publicKey,null);
    }

    /**
     * RSA公鑰加密
     */
    public static String encrypt( String str, String publicKey) throws Exception{
        //base64編碼的公鑰
        byte[] decoded = Base64.getDecoder().decode(publicKey);
        RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance(ALGORITHM).generatePublic(new X509EncodedKeySpec(decoded));
        //RSA加密
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        String outStr = Base64.getEncoder().encodeToString(cipher.doFinal(str.getBytes(CHARSET)));
        return outStr;
    }

    /**
     * RSA私鑰解密
     */
    public static String decrypt(String str, String privateKey) throws Exception{
        //64位解碼加密後的字符串
        byte[] inputByte = java.util.Base64.getDecoder().decode(str.getBytes(CHARSET));
        //base64編碼的私鑰
        byte[] decoded = Base64.getDecoder().decode(privateKey);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance(ALGORITHM).generatePrivate(new PKCS8EncodedKeySpec(decoded));
        //RSA解密
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        String outStr = new String(cipher.doFinal(inputByte));
        return outStr;
    }

    /**
     * 隨機生成密鑰對
     * 也可以用阿里的生成工具
     */
    public static void genKeyPair(Integer keySize) throws NoSuchAlgorithmException {
        //推薦 2048位以上，保證安全性
        if(keySize==null){
            keySize = KEY_SIZE_2048;
        }
        // KeyPairGenerator類用於生成公鑰和私鑰對，基於RSA算法生成對象
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(ALGORITHM);
        // 初始化密鑰對生成器，密鑰大小爲96-1024位
        keyPairGen.initialize(keySize, new SecureRandom());
        // 生成一個密鑰對，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();   // 得到私鑰
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  // 得到公鑰
        String publicKeyString = new String(Base64.getEncoder().encode(publicKey.getEncoded()));
        // 得到私鑰字符串
        String privateKeyString = new String(Base64.getEncoder().encode(privateKey.getEncoded()));
        // 將公鑰和私鑰保存到Map
        System.out.println("公鑰:"+publicKeyString);
        System.out.println("私鑰:"+privateKeyString);
    }

    //簡單測試
    public static void main(String[] args) throws Exception {
        String content = "我的數據";
        //支付寶RSA生成的公私鑰 也同樣適用，可以自行嘗試
        genKeyPair(null);
        String publicKey = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAkGv/70Te42PS5fyuLCNr/UiMtDqhasMZpmA92aDTWjh9RT5r4Kl3sKRO63RitWuEgFAZHljJUB9afEzWnP+EGpkeiq3SMpIfpUWy89nqZxUUyOg6aIvfEZBjKFFc3umM9uasFTLC8l4NCfDnlkpHxwQjc5emUGJ5ZnqqGOmrdP5se7dyO7QEtdI7/jfbzPDmMeWyegWE5iN8CHJh2V0foBur7gS/syTnbLFcRr3wzsbXh9RyLP9OMmHx9MO1fhTOnTZnN+xWXNggTgymoUM27+bZd/nrKaZNeUF50DIyTFEe6yqwkbtVf2jeR+CNjcWO+uP7CvTpDKk+9h3DZyZ5RwIDAQAB";
        String privateKey = "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";
        /*加解密測試*/
        String encryptContent = RSAUtils.encrypt(content, publicKey);
        System.out.println("加密後數據:\n" + encryptContent);
        String decryptContent = RSAUtils.decrypt(encryptContent,privateKey);
        System.out.println("解密後數據:\n"+decryptContent);
        /*加簽驗籤測試*/
        String signOriginalContent = "驗籤功能測試";
        String geneSignContent = RSAUtils.sign(signOriginalContent, privateKey);
        System.out.println("生成的簽名:\n"+geneSignContent);
        boolean valid = RSAUtils.isValid(signOriginalContent,geneSignContent, publicKey);
        System.out.println("結果驗籤:\n"+valid);
    }
}