rsa加密算法java实现

RSA加密算法的Java实现需要用到Java Cryptography Architecture (JCA)和Java Cryptography Extension (JCE)库。下面是一个简单的RSA加密算法Java实现的示例代码：

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

public class RSAEncryption {
    private static final int KEY_SIZE = 2048;

    public static void main(String[] args) throws Exception {
        String plainText = "Hello, world!";
        KeyPair keyPair = generateKeyPair();
        PublicKey publicKey = keyPair.getPublic();
        PrivateKey privateKey = keyPair.getPrivate();

        byte[] encryptedBytes = encrypt(plainText, publicKey);
        String encryptedText = new String(encryptedBytes);
        System.out.println("Encrypted text: " + encryptedText);

        byte[] decryptedBytes = decrypt(encryptedBytes, privateKey);
        String decryptedText = new String(decryptedBytes);
        System.out.println("Decrypted text: " + decryptedText);
    }

    private static KeyPair generateKeyPair() throws Exception {
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        keyPairGenerator.initialize(KEY_SIZE);
        return keyPairGenerator.generateKeyPair();
    }

    private static byte[] encrypt(String plainText, PublicKey publicKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        return cipher.doFinal(plainText.getBytes());
    }

    private static byte[] decrypt(byte[] encryptedBytes, PrivateKey privateKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        return cipher.doFinal(encryptedBytes);
    }
}

在这个例子中，我们使用2048位的RSA密钥对生成器生成公钥和私钥。然后，我们使用公钥加密明文，使用私钥解密密文。注意，在实际应用中，我们应该将密文转换为Base64字符串以便传输。