nodejs的crypto加密，设置认证数据标签，使用认证标签加密和解密，防止数据被串改

//直接上代码上说明

const crypto = require('crypto');

class Cipher {
//设置私有成员，#key随机的加密密码，#iv加密时所用的初始向量
    #key = crypto.randomBytes(32); // 256-bit key
    #iv = crypto.randomBytes(12); // 96-bit IV

    constructor(aad) {
    //设置附加的认证数据，任何字符
         this.aad = Buffer.from(aad); // 附加认证数据
    }
//加密
    encrypt(text) {
    //创建加密实例，经过身份验证的加密模式，就是认证数据（当前支持 GCM、CCM、OCB 和 chacha20-poly1305）
        const cipher = crypto.createCipheriv('aes-256-gcm', this.#key, this.#iv);
        cipher.setAAD(this.aad);

        let encrypted = cipher.update(text, 'utf8', 'hex');
        encrypted += cipher.final('hex');

        const authTag = cipher.getAuthTag(); // 获取认证标签
        return { encrypted, authTag }; // 返回密文和认证标签
    }
//解密
    decipher(encrypted, authTag) {
        const decipher = crypto.createDecipheriv('aes-256-gcm', this.#key, this.#iv);
        //解密也需要认证标签
        decipher.setAAD(this.aad);
        decipher.setAuthTag(authTag); // 设置认证标签

        try {
            let decrypted = decipher.update(encrypted, 'hex', 'utf8');
            decrypted += decipher.final('utf8');
            return decrypted;
        } catch (err) {
            console.error('Decryption failed:', err.message);
            return null;
        }
    }
}

// 使用示例
const c = new Cipher('metadata');
const { encrypted, authTag } = c.encrypt('hello'); // 加密
console.log('Encrypted:', encrypted);
console.log('Auth Tag:', authTag.toString('hex'));

const decrypted = c.decipher(encrypted, authTag); // 解密
console.log('Decrypted:', decrypted);