# 签名算法

 签名生成的通用步骤如下：

* 设所有发送或者接收到的数据为集合M，将集合M内非空参数值的参数按照参数名ASCII码从小到大排序（字典序），使用URL键值对的格式（即key1=value1\&key2=value2…）拼接成字符串stringA。
* 在stringA最后拼接上\&key={{app\_key}}得到stringSignTemp字符串，并对stringSignTemp进行MD5运算，得到sign值

特别注意以下重要规则：

* 参数名 ASCII 码从小到大排序（字典序）
* 参数名区分大小写

#### Demo

例如传递的参数如下：

```
app_id: 12345
amount_total: 1
out_trade_no: 123123123123

```

* 第一步：对参数按照key=value的格式，并按照参数名ASCII字典序排序如下

> app\_id=12345\&out\_trade\_no=123123123123\&amount\_total=1

* 第二步：对上一步中的字符串拼接\&key=密钥

> app\_id=12345\&out\_trade\_no=123123123123\&amount\_total=1\&key=xxxxxxxxx

* 第三步：对上一步中字符串取MD5值

> $sign = md5('app\_id=12345\&out\_trade\_no=123123123123\&amount\_total=1\&key=xxxxxxxxx');

#### 代码示例

php

```
// 签名方法
function sign(array $data, $key) {
    ksort($data);
    $sign = md5(urldecode(http_build_query($data)).'&key='.$key);
    return $sign;
}

// 用法示例
$data = [
    'app_id' => '12345',
    'amount_total' => 1,
    'out_trade_no' => '123123123123',
];

// 面包多支付 app_key
$key = 'xxxxxxxxxxx';

$sign = sign($data, $key);
```

python

```
# !/usr/bin/env Python3
# -*- coding: utf-8 -*-

import hashlib
from urllib.parse import urlencode,unquote
'''
签名算法
'''
# 签名算法
def sign(attributes, payjs_key):
    attributes_new = {k: attributes[k] for k in sorted(attributes.keys())}
    sign_str = "&".join(
        [f"{key}={attributes_new[key]}" for key in attributes_new.keys()]
    )
    return (
        hashlib.md5((sign_str + "&key=" + payjs_key).encode(encoding="utf-8"))
        .hexdigest()
    )

# 用法示例
data = {
    'app_id' : '12345',
    'amount_total' : 1,
    'out_trade_no' : '123123123123'
}

# 面包多支付 app_key
key = 'xxxxxxxxxxx'

sign = sign(data, key)
```

> 本文档参考 payjs 文档


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