如何用java实现ECDH双端通信加解密

ECDH (Elliptic Curve Diffie-Hellman) 是一种基于椭圆曲线的密钥交换算法，用于实现双方通信的加密与解密。下面是一个简单的 Java 实现。

首先，需要引入相关的库：

import java.math.BigInteger;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.ECGenParameterSpec;
import javax.crypto.Cipher;

然后，定义一个 ECDH 类，包含如下方法：

1. 生成密钥对

public static KeyPair generateKeyPair() throws NoSuchAlgorithmException, InvalidAlgorithmParameterException {
    KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("EC");
    ECGenParameterSpec ecGenParameterSpec = new ECGenParameterSpec("secp256k1"); // 使用secp256k1曲线
    keyPairGenerator.initialize(ecGenParameterSpec);
    return keyPairGenerator.generateKeyPair();
}

2. 生成共享密钥

public static byte[] generateSharedSecret(PrivateKey privateKey, PublicKey publicKey) throws Exception {
    Cipher cipher = Cipher.getInstance("ECIES");
    cipher.init(Cipher.ENCRYPT_MODE, publicKey);
    byte[] secret = cipher.doFinal();
    return secret;
}

3. 加密数据

public static byte[] encrypt(byte[] data, byte[] sharedSecret) throws Exception {
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    SecretKeySpec keySpec = new SecretKeySpec(sharedSecret, "AES");
    IvParameterSpec ivSpec = new IvParameterSpec(sharedSecret); // 使用共享密钥作为IV
    cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
    byte[] encryptedData = cipher.doFinal(data);
    return encryptedData;
}

4. 解密数据

public static byte[] decrypt(byte[] encryptedData, byte[] sharedSecret) throws Exception {
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    SecretKeySpec keySpec = new SecretKeySpec(sharedSecret, "AES");
    IvParameterSpec ivSpec = new IvParameterSpec(sharedSecret); // 使用共享密钥作为IV
    cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
    byte[] data = cipher.doFinal(encryptedData);
    return data;
}

完整代码如下：

import java.math.BigInteger;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.InvalidAlgorithmParameterException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.ECGenParameterSpec;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class ECDH {

    public static KeyPair generateKeyPair() throws NoSuchAlgorithmException, InvalidAlgorithmParameterException {
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("EC");
        ECGenParameterSpec ecGenParameterSpec = new ECGenParameterSpec("secp256k1"); // 使用secp256k1曲线
        keyPairGenerator.initialize(ecGenParameterSpec);
        return keyPairGenerator.generateKeyPair();
    }

    public static byte[] generateSharedSecret(PrivateKey privateKey, PublicKey publicKey) throws Exception {
        Cipher cipher = Cipher.getInstance("ECIES");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        byte[] secret = cipher.doFinal();
        return secret;
    }

    public static byte[] encrypt(byte[] data, byte[] sharedSecret) throws Exception {
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        SecretKeySpec keySpec = new SecretKeySpec(sharedSecret, "AES");
        IvParameterSpec ivSpec = new IvParameterSpec(sharedSecret); // 使用共享密钥作为IV
        cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
        byte[] encryptedData = cipher.doFinal(data);
        return encryptedData;
    }

    public static byte[] decrypt(byte[] encryptedData, byte[] sharedSecret) throws Exception {
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        SecretKeySpec keySpec = new SecretKeySpec(sharedSecret, "AES");
        IvParameterSpec ivSpec = new IvParameterSpec(sharedSecret); // 使用共享密钥作为IV
        cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
        byte[] data = cipher.doFinal(encryptedData);
        return data;
    }

    public static void main(String[] args) throws Exception {
        // 生成密钥对
        KeyPair keyPairA = generateKeyPair();
        KeyPair keyPairB = generateKeyPair();

        // A计算共享密钥
        byte[] secretA = generateSharedSecret(keyPairA.getPrivate(), keyPairB.getPublic());

        // B计算共享密钥
        byte[] secretB = generateSharedSecret(keyPairB.getPrivate(), keyPairA.getPublic());

        // 加密数据
        byte[] data = "Hello, ECDH!".getBytes();
        byte[] encryptedData = encrypt(data, secretA);

        // 解密数据
        byte[] decryptedData = decrypt(encryptedData, secretB);
        System.out.println(new String(decryptedData)); // 输出：Hello, ECDH!
    }

}

注意：此代码仅为示例，实际应用中需要根据具体情况进行调整。另外，ECDH 算法的安全性与曲线的选择有关，需要根据实际需求选择合适的曲线。