Java实现rsa数字签名代码和验签

RSA数字签名是非常重要的加密算法之一，以下是Java实现RSA数字签名的代码示例：

## 数字签名

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.security.Key;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

public class RSAUtil {
    private static final String ALGORITHM = "RSA";
    private static final String SIGNATURE_ALGORITHM = "SHA1WithRSA";

    /**
     * 从文件中加载私钥
     *
     * @param privateKeyFile 私钥文件
     * @return 私钥
     * @throws Exception
     */
    public static PrivateKey loadPrivateKeyFromFile(File privateKeyFile) throws Exception {
        FileInputStream fis = new FileInputStream(privateKeyFile);
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int len;
        while ((len = fis.read(buffer)) != -1) {
            bos.write(buffer, 0, len);
        }
        fis.close();
        bos.close();
        byte[] privateKeyBytes = bos.toByteArray();
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(privateKeyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
        return keyFactory.generatePrivate(pkcs8KeySpec);
    }

    /**
     * 从文件中加载公钥
     *
     * @param publicKeyFile 公钥文件
     * @return 公钥
     * @throws Exception
     */
    public static PublicKey loadPublicKeyFromFile(File publicKeyFile) throws Exception {
        FileInputStream fis = new FileInputStream(publicKeyFile);
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int len;
        while ((len = fis.read(buffer)) != -1) {
            bos.write(buffer, 0, len);
        }
        fis.close();
        bos.close();
        byte[] publicKeyBytes = bos.toByteArray();
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(publicKeyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
        return keyFactory.generatePublic(x509KeySpec);
    }

    /**
     * 对数据进行数字签名
     *
     * @param data          数据
     * @param privateKey    私钥
     * @return 数字签名
     * @throws Exception
     */
    public static byte[] sign(byte[] data, PrivateKey privateKey) throws Exception {
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initSign(privateKey);
        signature.update(data);
        return signature.sign();
    }

    /**
     * 验证数字签名
     *
     * @param data         数据
     * @param publicKey    公钥
     * @param signedData   数字签名
     * @return 是否验证通过
     * @throws Exception
     */
    public static boolean verify(byte[] data, PublicKey publicKey, byte[] signedData) throws Exception {
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initVerify(publicKey);
        signature.update(data);
        return signature.verify(signedData);
    }
}

## 使用示例

import java.io.File;
import java.nio.charset.StandardCharsets;
import java.security.PrivateKey;
import java.security.PublicKey;

public class Main {
    public static void main(String[] args) throws Exception {
        // 加载私钥
        File privateKeyFile = new File("private_key.txt");
        PrivateKey privateKey = RSAUtil.loadPrivateKeyFromFile(privateKeyFile);

        // 加载公钥
        File publicKeyFile = new File("public_key.txt");
        PublicKey publicKey = RSAUtil.loadPublicKeyFromFile(publicKeyFile);

        // 待签名数据
        String data = "Hello, World!";
        byte[] dataBytes = data.getBytes(StandardCharsets.UTF_8);

        // 数字签名
        byte[] signedData = RSAUtil.sign(dataBytes, privateKey);

        // 验证数字签名
        boolean verified = RSAUtil.verify(dataBytes, publicKey, signedData);
        System.out.println("Verified: " + verified);
    }
}

以上代码示例中，我们使用了`RSAUtil`类中的`loadPrivateKeyFromFile`方法和`loadPublicKeyFromFile`方法分别从私钥文件和公钥文件中加载私钥和公钥。然后我们使用`sign`方法对待签名数据进行数字签名，使用`verify`方法对签名结果进行验证。

切记，要使用自己的密钥对，不要使用他人的密钥对。