SpringBoot集成ECDH密钥交换

简介

对称加解密算法都需要一把秘钥，但是很多情况下，互联网环境不适合传输这把对称密码，有密钥泄露的风险，为了解决这个问题ECDH密钥交换应运而生

EC：Elliptic Curve——椭圆曲线，生成密钥的方法

DH：Diffie-Hellman Key Exchange——交换密钥的方法

设计

数据传输的两方服务端（Server）和客户端（Client）

服务端生成密钥对Server-Public和Servier-Private

客户端生成密钥对Client-Public和Client-Private

客户端获取服务端的公钥和客户端的私钥进行计算CaculateKey(Server-Public，Client-Private)出共享密钥ShareKey1

服务端获取客户端的公钥和服务端的私钥进行计算CaculateKey(Client-Public，Server-Private)出共享密钥ShareKey2

ShareKey1和ShareKey2必定一致，ShareKey就是双方传输数据进行AES加密时的密钥

实现

生成密钥对

后端

    public static ECDHKeyInfo generateKeyInfo(){
        ECDHKeyInfo keyInfo = new ECDHKeyInfo();
        try{
            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("EC");
            ECGenParameterSpec ecSpec = new ECGenParameterSpec("secp256r1");
            keyPairGenerator.initialize(ecSpec, new SecureRandom());
            KeyPair kp = keyPairGenerator.generateKeyPair();
            ECPublicKey ecPublicKey = (ECPublicKey) kp.getPublic();
            ECPrivateKey ecPrivateKey = (ECPrivateKey) kp.getPrivate();
            // 获取公钥点的x和y坐标
            BigInteger x = ecPublicKey.getW().getAffineX();
            BigInteger y = ecPublicKey.getW().getAffineY();
            // 将x和y坐标转换为十六进制字符串
            String xHex = x.toString(16);
            String yHex = y.toString(16);
            String publicKey = xHex + "|" + yHex;
            String privateKey = Base64.getEncoder().encodeToString(ecPrivateKey.getEncoded());
            keyInfo.setPublicKey(publicKey);
            keyInfo.setPrivateKey(privateKey);
        }catch (Exception e){
            e.printStackTrace();
        }
        return keyInfo;
    }
   
    public static class ECDHKeyInfo{
        private String publicKey;
        private String privateKey;

        public String getPublicKey() {
            return publicKey;
        }

        public void setPublicKey(String publicKey) {
            this.publicKey = publicKey;
        }

        public String getPrivateKey() {
            return privateKey;
        }

        public void setPrivateKey(String privateKey) {
            this.privateKey = privateKey;
        }
    }
   

前端

引入elliptic.js（https://cdn.bootcdn.net/ajax/libs/elliptic/6.5.6/elliptic.js）

    const EC = elliptic.ec;
    const ec = new EC('p256'); // P-256曲线

    // 生成密钥对
    const keyPair = ec.genKeyPair();
	const publicKey = keyPair.getPublic().getX().toString('hex') + "|" + keyPair.getPublic().getY().toString('hex');

共享密钥计算

后端

    public static String caculateShareKey(String serverPrivateKey,String receivePublicKey){
        String shareKey = "";
        try{
            // 1. 后端私钥 Base64 字符串
            // 2. 从 Base64 恢复后端私钥
            ECPrivateKey privKey = loadPrivateKeyFromBase64(serverPrivateKey);
            // 3. 前端传递的公钥坐标 (x 和 y 坐标，假设为十六进制字符串)
            // 假设这是从前端接收到的公钥的 x 和 y 坐标
            String xHex = receivePublicKey.split("\\|")[0];  // 用前端传递的 x 坐标替换
            String yHex = receivePublicKey.split("\\|")[1];  // 用前端传递的 y 坐标替换
            // 4. 将 x 和 y 转换为 BigInteger
            BigInteger x = new BigInteger(xHex, 16);
            BigInteger y = new BigInteger(yHex, 16);
            // 5. 创建 ECPoint 对象 (公钥坐标)
            ECPoint ecPoint = new ECPoint(x, y);
            // 6. 获取 EC 参数（例如 secp256r1）
            ECParameterSpec ecSpec = getECParameterSpec();
            // 7. 恢复公钥
            ECPublicKey pubKey = recoverPublicKey(ecPoint, ecSpec);
            // 8. 使用 ECDH 计算共享密钥
            byte[] sharedSecret = calculateSharedSecret(privKey, pubKey);
            // 9. 打印共享密钥
            shareKey = bytesToHex(sharedSecret);
        }catch (Exception e){
            e.printStackTrace();
        }
        return shareKey;
    }
    
    // 从 Base64 加载 ECPrivateKey
    private static ECPrivateKey loadPrivateKeyFromBase64(String privateKeyBase64) throws Exception {
        byte[] decodedKey = Base64.getDecoder().decode(privateKeyBase64);
        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(decodedKey);
        KeyFactory keyFactory = KeyFactory.getInstance("EC");
        return (ECPrivateKey) keyFactory.generatePrivate(keySpec);
    }
    // 获取 EC 参数（例如 secp256r1）
    private static ECParameterSpec getECParameterSpec() throws Exception {
        // 手动指定 EC 曲线（例如 secp256r1）
        AlgorithmParameters params = AlgorithmParameters.getInstance("EC");
        params.init(new ECGenParameterSpec("secp256r1"));  // 使用标准的 P-256 曲线
        return params.getParameterSpec(ECParameterSpec.class);
    }
    // 恢复公钥
    private static ECPublicKey recoverPublicKey(ECPoint ecPoint, ECParameterSpec ecSpec) throws Exception {
        ECPublicKeySpec pubKeySpec = new ECPublicKeySpec(ecPoint, ecSpec);
        KeyFactory keyFactory = KeyFactory.getInstance("EC");
        return (ECPublicKey) keyFactory.generatePublic(pubKeySpec);
    }
    // 使用 ECDH 计算共享密钥
    private static byte[] calculateSharedSecret(ECPrivateKey privKey, ECPublicKey pubKey) throws Exception {
        KeyAgreement keyAgreement = KeyAgreement.getInstance("ECDH");
        keyAgreement.init(privKey);
        keyAgreement.doPhase(pubKey, true);
        return keyAgreement.generateSecret();
    }

    // 将字节数组转换为十六进制字符串
    private static String bytesToHex(byte[] bytes) {
        StringBuilder hexString = new StringBuilder();
        for (byte b : bytes) {
            hexString.append(String.format("%02x", b));
        }
        return hexString.toString();
    }    

前端

    var keyArray = serverPublicPointKey.split("|")
    const otherKey = ec.keyFromPublic({ x: keyArray[0], y: keyArray[1] }, 'hex');
    const sharedSecret = keyPair.derive(otherKey.getPublic());

AES加密

后端

    public static String encryptData(String data,String shareKey){
        String result = "";
        try{
            MessageDigest digest = MessageDigest.getInstance("SHA-256");
            byte[] aesKey = digest.digest(shareKey.getBytes());  // 获取 256 位密钥
            SecretKey key = new SecretKeySpec(aesKey, "AES");
            byte[] resultData = encrypt(data,key);
            result = Base64.getEncoder().encodeToString(resultData);
        }catch (Exception e){
            e.printStackTrace();
        }
        return result;
    }

    public static String decryptData(String data,String shareKey){
        String result = "";
        try{
            MessageDigest digest = MessageDigest.getInstance("SHA-256");
            byte[] aesKey = digest.digest(shareKey.getBytes());  // 获取 256 位密钥
            SecretKey key = new SecretKeySpec(aesKey, "AES");
            byte[] resultData = decrypt(Base64.getDecoder().decode(data),key);
            result = new String(resultData);
        }catch (Exception e){
            e.printStackTrace();
        }
        return result;
    }
    
    private static final String KEY_ALGORITHM = "AES";
    private static final String CIPHER_ALGORITHM = "AES/CBC/PKCS5Padding";
    private static final String IV = "0102030405060708"; // 16 bytes key

    // 使用AES密钥加密数据
    private static byte[] encrypt(String plaintext, SecretKey aesKey) throws Exception {
        SecretKeySpec keySpec = new SecretKeySpec(aesKey.getEncoded(), KEY_ALGORITHM);
        IvParameterSpec iv = new IvParameterSpec(IV.getBytes());
        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, keySpec, iv);
        byte[] encrypted = cipher.doFinal(plaintext.getBytes());
        return encrypted;
    }

    // 使用AES密钥解密数据
    private static byte[] decrypt(byte[] encryptedData, SecretKey aesKey) throws Exception {
        SecretKeySpec keySpec = new SecretKeySpec(aesKey.getEncoded(), KEY_ALGORITHM);
        IvParameterSpec iv = new IvParameterSpec(IV.getBytes());
        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, keySpec, iv);
        byte[] original = cipher.doFinal(encryptedData);
        return original;
    }    

前端

引入crypto-js.min.js（https://cdnjs.cloudflare.com/ajax/libs/crypto-js/4.1.1/crypto-js.min.js）

function encryptByECDH(message, shareKey) {
    const aesKey = CryptoJS.SHA256(shareKey);
    const key = CryptoJS.enc.Base64.parse(aesKey.toString(CryptoJS.enc.Base64));
    return encryptByAES(message,key)
}

function decryptByECDH(message, shareKey) {
    const aesKey = CryptoJS.SHA256(shareKey);
    const key = CryptoJS.enc.Base64.parse(aesKey.toString(CryptoJS.enc.Base64));
    return decryptByAES(message,key)
}

function encryptByAES(message, key) {
    const iv = CryptoJS.enc.Utf8.parse("0102030405060708");
    const encrypted = CryptoJS.AES.encrypt(message, key, { iv: iv , mode: CryptoJS.mode.CBC, padding: CryptoJS.pad.Pkcs7 });
    return encrypted.toString();
}

function decryptByAES(message, key) {
    const iv = CryptoJS.enc.Utf8.parse("0102030405060708");
    const bytes = CryptoJS.AES.decrypt(message, key, { iv: iv, mode: CryptoJS.mode.CBC, padding: CryptoJS.pad.Pkcs7 });
    const originalText = bytes.toString(CryptoJS.enc.Utf8);
    return originalText;
}

注意

• 前端生成的密钥对和后端生成的密钥对形式不一致，需要将前端的公钥拆解成坐标点到后端进行公钥还原
• 同理后端的公钥也要拆分成坐标点传输到前端进行计算
• 生成的ShareKey共享密钥为了满足AES的密钥长度要求需要进行Share256计算
• 前后端AES互通需要保证IV向量为同一值