Java – RSA工具类和操作方法

在Java中进行公钥加密私钥解密和私钥加密公钥解密操作需要使用非对称加密算法（例如RSA）和相关的密钥管理。下面是一个示例Java类，展示了如何创建一个工具类，其中包含这些操作的方法：

import java.security.*;
import javax.crypto.Cipher;
import java.util.Base64;

public class Main {

    public static void main(String[] args) throws Exception {
        // 生成RSA密钥对
        KeyPair keyPair = generateRSAKeyPair();

        // 获取公钥和私钥
        PublicKey publicKey = keyPair.getPublic();
        PrivateKey privateKey = keyPair.getPrivate();

        // 要加密的明文
        String plaintext = "你好，我是需要测试加解密的文本！";

        // 使用公钥加密明文
        byte[] encryptedDataWithPublicKey = encryptWithPublicKey(plaintext, publicKey);
        // 编码为Base64字符串
        String base64EncryptedDataWithPublicKey = Base64.getEncoder().encodeToString(encryptedDataWithPublicKey);

        // 解码为原始字符串
        byte[] decodedBytesBase64EncryptedDataWithPublicKey = Base64.getDecoder().decode(base64EncryptedDataWithPublicKey);
        // 使用私钥解密密文
        String decryptedTextWithPrivateKey = decryptWithPrivateKey(decodedBytesBase64EncryptedDataWithPublicKey, privateKey);

        // 打印加解密结果
        System.out.println("Encrypted Text with Public Key: " + base64EncryptedDataWithPublicKey);
        System.out.println("Decrypted Text with Private Key: " + decryptedTextWithPrivateKey);

        // 使用私钥加密明文
        byte[] encryptedDataWithPrivateKey = encryptWithPrivateKey(plaintext, privateKey);
        // 编码为Base64字符串
        String base64EncryptedDataWithPrivateKey = Base64.getEncoder().encodeToString(encryptedDataWithPrivateKey);

        // 解码为原始字符串
        byte[] decodedBytesBase64EncryptedDataWithPrivateKey = Base64.getDecoder().decode(base64EncryptedDataWithPrivateKey);
        // 使用公钥解密密文
        String decryptedTextWithPublicKey = decryptWithPublicKey(decodedBytesBase64EncryptedDataWithPrivateKey, publicKey);

        // 打印加解密结果
        System.out.println("Encrypted Text with Private Key: " + base64EncryptedDataWithPrivateKey);
        System.out.println("Decrypted Text with Public Key: " + decryptedTextWithPublicKey);
    }

    // 生成RSA密钥对
    public static KeyPair generateRSAKeyPair() throws Exception {
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        keyPairGenerator.initialize(2048); // 设置密钥长度
        return keyPairGenerator.generateKeyPair();
    }

    // 使用公钥加密明文
    public static byte[] encryptWithPublicKey(String plaintext, PublicKey publicKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        return cipher.doFinal(plaintext.getBytes());
    }

    // 使用私钥解密密文
    public static String decryptWithPrivateKey(byte[] encryptedData, PrivateKey privateKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        byte[] decryptedData = cipher.doFinal(encryptedData);
        return new String(decryptedData);
    }

    // 使用私钥加密明文
    public static byte[] encryptWithPrivateKey(String plaintext, PrivateKey privateKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);
        return cipher.doFinal(plaintext.getBytes());
    }

    // 使用公钥解密密文
    public static String decryptWithPublicKey(byte[] encryptedData, PublicKey publicKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, publicKey);
        byte[] decryptedData = cipher.doFinal(encryptedData);
        return new String(decryptedData);
    }
}