256 lines
6.9 KiB
Markdown
256 lines
6.9 KiB
Markdown
# 常见加密模式识别与还原
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## 快速识别表
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| 特征 | 可能的算法 | 验证方法 |
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|------|-----------|---------|
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| 32位十六进制 | MD5 | 用已知输入验证 |
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| 40位十六进制 | SHA-1 | 同上 |
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| 64位十六进制 | SHA-256 | 同上 |
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| 128位十六进制 | SHA-512 | 同上 |
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| `=` 结尾，含 `A-Za-z0-9+/` | Base64 | 直接 atob 解码 |
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| `=` 结尾，含 `A-Za-z0-9-_` | Base64url | 替换 `-_` 为 `+/` 后解码 |
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| 固定长度密文，16字节倍数 | AES (128-bit key) | 寻找 key/iv |
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| 固定长度密文，8字节倍数 | DES / 3DES | 寻找 8字节 key |
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| 超长数字字符串 | RSA | 寻找公钥 |
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| `CryptoJS` 关键词 | CryptoJS 库 | 直接搜索源码 |
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## 1. MD5
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### 标准 MD5
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```javascript
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const crypto = require('crypto');
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function md5(str) {
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return crypto.createHash('md5').update(str).digest('hex');
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}
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```
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### 自定义 MD5（非标准实现）
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某些网站修改了 MD5 的内部参数（如 chrsz=16），导致输出与标准 MD5 不同。
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**识别方法**：用相同输入对比标准 MD5 输出，如果不一致则为自定义实现。
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**还原策略**：必须提取原始 JS 实现，在 Node.js 中直接执行。
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### 常见 MD5 签名模式
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```javascript
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// 模式1：简单拼接
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sign = md5(param1 + param2 + timestamp + secret)
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// 模式2：排序拼接
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params = Object.keys(data).sort().map(k => k + '=' + data[k]).join('&')
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sign = md5(params + secret)
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// 模式3：嵌套哈希
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sign = md5(md5(password) + timestamp)
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```
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## 2. HMAC
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```javascript
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const crypto = require('crypto');
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function hmacSha256(message, secret) {
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return crypto.createHmac('sha256', secret).update(message).digest('hex');
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}
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```
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**识别特征**：搜索 `HMAC`、`createHmac`、`CryptoJS.HmacSHA256`
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## 3. AES
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### AES-CBC
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```javascript
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const crypto = require('crypto');
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function aesEncrypt(plaintext, key, iv) {
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const cipher = crypto.createCipheriv('aes-128-cbc', key, iv);
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cipher.setAutoPadding(true); // PKCS7
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let encrypted = cipher.update(plaintext, 'utf8', 'base64');
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encrypted += cipher.final('base64');
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return encrypted;
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}
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function aesDecrypt(ciphertext, key, iv) {
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const decipher = crypto.createDecipheriv('aes-128-cbc', key, iv);
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decipher.setAutoPadding(true);
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let decrypted = decipher.update(ciphertext, 'base64', 'utf8');
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decrypted += decipher.final('utf8');
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return decrypted;
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}
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```
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### AES-ECB
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```javascript
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function aesEcbEncrypt(plaintext, key) {
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const cipher = crypto.createCipheriv('aes-128-ecb', key, null);
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cipher.setAutoPadding(true);
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let encrypted = cipher.update(plaintext, 'utf8', 'base64');
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encrypted += cipher.final('base64');
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return encrypted;
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}
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```
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### CryptoJS 兼容
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```javascript
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const CryptoJS = require('crypto-js');
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// CryptoJS 默认使用 PKCS7 填充
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const encrypted = CryptoJS.AES.encrypt(plaintext, CryptoJS.enc.Utf8.parse(key), {
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iv: CryptoJS.enc.Utf8.parse(iv),
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mode: CryptoJS.mode.CBC,
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padding: CryptoJS.pad.Pkcs7
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}).toString();
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```
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**关键参数识别**：
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- key 长度：16字节=AES-128，24字节=AES-192，32字节=AES-256
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- iv 长度：固定16字节
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- 模式：CBC（需要iv）、ECB（不需要iv）、CTR、GCM
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- 填充：PKCS7（最常见）、ZeroPadding、NoPadding
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- 输出格式：Base64（最常见）、Hex
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## 4. DES / 3DES
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```javascript
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function desEncrypt(plaintext, key) {
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const cipher = crypto.createCipheriv('des-ecb', key, null); // 8字节key
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cipher.setAutoPadding(true);
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let encrypted = cipher.update(plaintext, 'utf8', 'base64');
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encrypted += cipher.final('base64');
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return encrypted;
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}
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function tripleDesEncrypt(plaintext, key, iv) {
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const cipher = crypto.createCipheriv('des-ede3-cbc', key, iv); // 24字节key
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cipher.setAutoPadding(true);
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let encrypted = cipher.update(plaintext, 'utf8', 'base64');
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encrypted += cipher.final('base64');
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return encrypted;
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}
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```
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## 5. RSA
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```javascript
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const crypto = require('crypto');
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function rsaEncrypt(plaintext, publicKey) {
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const buffer = Buffer.from(plaintext, 'utf8');
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const encrypted = crypto.publicEncrypt({
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key: publicKey,
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padding: crypto.constants.RSA_PKCS1_PADDING
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}, buffer);
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return encrypted.toString('base64');
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}
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```
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**使用 node-forge（更灵活）**：
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```javascript
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const forge = require('node-forge');
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function rsaEncrypt(plaintext, publicKeyPem) {
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const publicKey = forge.pki.publicKeyFromPem(publicKeyPem);
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const encrypted = publicKey.encrypt(plaintext, 'RSAES-PKCS1-V1_5');
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return forge.util.encode64(encrypted);
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}
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```
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**常见 RSA 公钥格式**：
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- PEM 格式（`-----BEGIN PUBLIC KEY-----`）
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- 模数(n) + 指数(e) 格式（需要手动构造 PEM）
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## 6. Base64 变体
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```javascript
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// 标准 Base64
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const encoded = Buffer.from(str).toString('base64');
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const decoded = Buffer.from(encoded, 'base64').toString();
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// Base64url（URL安全变体）
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function base64url(str) {
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return Buffer.from(str).toString('base64')
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.replace(/\+/g, '-').replace(/\//g, '_').replace(/=/g, '');
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}
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// 自定义字符表 Base64
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function customBase64(str, table) {
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const std = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
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const b64 = Buffer.from(str).toString('base64');
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return b64.split('').map(c => {
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const idx = std.indexOf(c);
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return idx >= 0 ? table[idx] : c;
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}).join('');
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}
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```
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## 7. 异或加密（XOR）
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```javascript
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function xorEncrypt(plaintext, key) {
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const result = [];
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for (let i = 0; i < plaintext.length; i++) {
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result.push(plaintext.charCodeAt(i) ^ key.charCodeAt(i % key.length));
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}
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return Buffer.from(result).toString('hex');
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}
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```
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## 8. RC4
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```javascript
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function rc4(data, key) {
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const s = Array.from({ length: 256 }, (_, i) => i);
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let j = 0;
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for (let i = 0; i < 256; i++) {
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j = (j + s[i] + key.charCodeAt(i % key.length)) % 256;
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[s[i], s[j]] = [s[j], s[i]];
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}
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let i = 0; j = 0;
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const result = [];
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for (let k = 0; k < data.length; k++) {
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i = (i + 1) % 256;
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j = (j + s[i]) % 256;
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[s[i], s[j]] = [s[j], s[i]];
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result.push(data.charCodeAt(k) ^ s[(s[i] + s[j]) % 256]);
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}
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return Buffer.from(result);
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}
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```
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## 9. 时间戳处理
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```javascript
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// 毫秒级（13位）
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const tsMs = Date.now(); // 1710000000000
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// 秒级（10位）
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const tsSec = Math.floor(Date.now() / 1000); // 1710000000
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// 注意：某些网站使用服务端时间戳，需要从响应头或接口获取
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```
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## 10. 参数签名常见拼接模式
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```javascript
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// 模式1：固定格式
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sign = md5(`page=${page}&t=${timestamp}&key=${secret}`)
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// 模式2：所有参数排序拼接
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const params = { page: 1, size: 10, t: Date.now() };
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const str = Object.keys(params).sort().map(k => `${k}=${params[k]}`).join('&');
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sign = md5(str + secret)
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// 模式3：JSON 字符串
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sign = md5(JSON.stringify(data) + secret)
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// 模式4：管道分隔
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sign = md5(`${page}|${timestamp}|${secret}`)
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```
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