非对称密钥：应用场景

public class EncryptionAndSignatureExample {

public static void main(String[] args) throws Exception {
    // 生成公私钥对
    KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
    keyPairGenerator.initialize(1024);
    KeyPair keyPair = keyPairGenerator.generateKeyPair();
    PrivateKey privateKey = keyPair.getPrivate();
    PublicKey publicKey = keyPair.getPublic();
    System.out.println("公钥：" + publicKey);
    System.out.println("私钥：" + privateKey);

    // 私钥加密、公钥验签示例
    String message = "Test message for signature";
    byte[] signature = sign(privateKey, message);
    boolean isVerified = verify(publicKey, message, signature);

    System.out.println("私钥加密、公钥验签结果: " + isVerified);

    // 公钥加密、私钥解密示例
    String encryptedMessage = encrypt(publicKey, "Secret message");
    String decryptedMessage = decrypt(privateKey, encryptedMessage);

    System.out.println("公钥加密、私钥解密后的消息: " + decryptedMessage);
}

public static byte[] sign(PrivateKey privateKey, String message) throws Exception {
    Signature signature = Signature.getInstance("SHA256withRSA");
    signature.initSign(privateKey);
    signature.update(message.getBytes());
    return signature.sign();
}

public static boolean verify(PublicKey publicKey, String message, byte[] signature) throws Exception {
    Signature verification = Signature.getInstance("SHA256withRSA");
    verification.initVerify(publicKey);
    verification.update(message.getBytes());
    return verification.verify(signature);
}

public static String encrypt(PublicKey publicKey, String message) throws Exception {
    // 这里简单模拟加密，实际应用中需使用更完善的加密逻辑
    return message + "_encrypted";
}

public static String decrypt(PrivateKey privateKey, String encryptedMessage) throws Exception {
    // 这里简单模拟解密，实际应用中需使用更完善的解密逻辑
    return encryptedMessage.replace("_encrypted", "");
}
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}