java.security.*篇(2) RSA签名与校验demo

 private final String ALGORITHM_NAME = "RSA";
 private static final String MD5_RSA = "MD5withRSA";

<dependency>
    <groupId>commons-codec</groupId>
    <artifactId>commons-codec</artifactId>
    <version>1.11</version>
</dependency>

/**
     * @description: demos of jdk8 java.security KeyPairGenerator KeyPair
     * RSAPrivateKey RSAPublicKey X509EncodedKeySpec X509EncodedKeySpec PKCS8EncodedKeySpec Signature
     * ras private_key sign and public_key verify  用ras 私钥签名 公钥验证数据和签名是否匹配，也就是是否数据被篡改
     */
 
    @Test
    public void testRsaSignAndPublicVerify() throws Exception {
 
        String message = "这是要签名的字符串";
 
        // 初始化密钥生成器
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM_NAME);
 
        // 设置大小
        keyPairGenerator.initialize(1024);
 
        // 生成密钥对
        KeyPair keyPair = keyPairGenerator.genKeyPair();
 
        // 获取私钥
        PrivateKey privateKey = keyPair.getPrivate();
 
        // 获取公钥
        PublicKey publicKey = keyPair.getPublic();
 
        // 私钥字符串
        String privateKeyStr = Base64.encodeBase64URLSafeString(privateKey.getEncoded());
 
        // 公钥字符串
        String publicKeyStr = Base64.encodeBase64URLSafeString(publicKey.getEncoded());
 
        //用公钥签名字符串
        String signStr = new String(privateKeySign(privateKeyStr,message));
 
        //用私钥签名字符串
        boolean verify = publicKeyVerify(publicKeyStr,signStr,message);
 
        //签名校验结果为true
        Assert.assertTrue(verify);
 
        //模拟串改message
        verify = publicKeyVerify(publicKeyStr,signStr,message+"change");
 
        //签名校验结果为false
        Assert.assertFalse(verify);
    }

 /**
     * @description private key sign
     * 私钥签名：实际情况一般是私钥和公钥是提前生成好的，我们需要读取配置文件或者输入值获取公钥私钥字符串去加密解密，因为传入参数需要是字符串，
     * privateKey publicKey 对象进行后续操作
     * Signature 初始化，并执行sign() 返回base64 bytes
     **/
    private byte[] privateKeySign(String privateKeyStr, String message) throws NoSuchAlgorithmException, InvalidKeySpecException, InvalidKeyException, UnsupportedEncodingException, SignatureException {
 
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM_NAME);
        PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(privateKeyStr));
        PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
        Signature signature = Signature.getInstance(MD5_RSA);
 
        signature.initSign(privateKey);
        signature.update(message.getBytes());
        return Base64.encodeBase64(signature.sign());
    }

 /**
     * @description public key verify
     * 公钥验证：实际情况一般是私钥和公钥是提前生成好的，我们需要读取配置文件或者输入值获取公钥私钥字符串去加密解密，因为传入参数需要是字符串，
     * privateKey publicKey 对象进行后续操作
     * Signature 初始化并执行verify 后验证message 是否与签名后的signStr 匹配
     **/
    private boolean publicKeyVerify(String publicKeyStr, String signStr, String message) throws NoSuchAlgorithmException, InvalidKeySpecException, InvalidKeyException, SignatureException {
 
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM_NAME);
        X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(Base64.decodeBase64(publicKeyStr));
        PublicKey publicKey =  keyFactory.generatePublic(x509EncodedKeySpec);
        Signature signature = Signature.getInstance(MD5_RSA);
        signature.initVerify(publicKey);
        signature.update(message.getBytes());
        return signature.verify(Base64.decodeBase64(signStr.getBytes()));
    }