在java和SHA256中对字符串签名

import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;

public class SignatureExample {
    public static void main(String[] args) throws Exception {
        // 生成密钥对
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        keyPairGenerator.initialize(2048);
        KeyPair keyPair = keyPairGenerator.generateKeyPair();
        PublicKey publicKey = keyPair.getPublic();
        PrivateKey privateKey = keyPair.getPrivate();

        // 待签名的字符串
        String message = "Hello, World!";

        // 使用私钥进行签名
        Signature signature = Signature.getInstance("SHA256withRSA");
        signature.initSign(privateKey);
        signature.update(message.getBytes());
        byte[] signatureBytes = signature.sign();

        // 使用公钥进行验证
        Signature verification = Signature.getInstance("SHA256withRSA");
        verification.initVerify(publicKey);
        verification.update(message.getBytes());
        boolean isVerified = verification.verify(signatureBytes);

        System.out.println("Signature verified: " + isVerified);
    }
}