Java RSA 加解密：前端加密，后端解密 (支持 JDK6)

在Java中，可以使用Java Cryptography Architecture（JCA）和Java Cryptography Extension（JCE）提供的API来实现RSA加解密。

以下是一个简单的示例：

前端加密：

import javax.crypto.Cipher;
import java.security.KeyPairGenerator;
import java.security.KeyPair;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.util.Base64;

public class RASUtils {

    private static final String ALGORITHM = "RSA";
    private static final int KEY_SIZE = 2048;

    public static String encrypt(String message, PublicKey publicKey) throws Exception {
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        byte[] encryptedMessage = cipher.doFinal(message.getBytes());
        return Base64.getEncoder().encodeToString(encryptedMessage);
    }

    public static KeyPair generateKeyPair() throws Exception {
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);
        keyPairGenerator.initialize(KEY_SIZE);
        return keyPairGenerator.generateKeyPair();
    }
}

后端解密：

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

public class RASUtils {

    private static final String ALGORITHM = "RSA";

    public static String decrypt(String encryptedMessage, PrivateKey privateKey) throws Exception {
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        byte[] decryptedMessage = cipher.doFinal(Base64.getDecoder().decode(encryptedMessage));
        return new String(decryptedMessage);
    }
}

使用示例：

import java.security.KeyPair;
import java.security.PrivateKey;
import java.security.PublicKey;

public class Main {

    public static void main(String[] args) throws Exception {
        // 生成公私钥对
        KeyPair keyPair = RASUtils.generateKeyPair();
        PublicKey publicKey = keyPair.getPublic();
        PrivateKey privateKey = keyPair.getPrivate();

        // 前端加密密码
        String password = "myPassword";
        String encryptedPassword = RASUtils.encrypt(password, publicKey);

        // 后端解密密码
        String decryptedPassword = RASUtils.decrypt(encryptedPassword, privateKey);

        System.out.println("原始密码：" + password);
        System.out.println("加密后的密码：" + encryptedPassword);
        System.out.println("解密后的密码：" + decryptedPassword);
    }
}

**注意：**在使用JDK6时，需要下载并安装Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files，以支持更长的密钥大小。