javascript - alidayu阿里大鱼的短信签名如何生成

因为是相对较老的asp程序，只能自助了
对于阿里大鱼没有提供现成api的其他框架和语言，这个问题是共通的

按照阿里大鱼的API调用方法，却老是调不出来，好几天了，真的很挠头和沮丧
谢谢不吝赐教

关键字段如下：
app_secret = "3ea815c1a0aeb73bc7fabe63d104e451"

app_key = "23333126"
method = "alibaba.aliqin.fc.sms.num.send"
rec_num = "15831687958"
sign_method = "md5"
sms_free_sign_name = "身份验证"
sms_param = "{""code"":""1234"",""product"":""博览天下网""}"
sms_template_code = "SMS_6740688"
sms_type = "normal"
timestamp = "2016-04-07 23:36:11"
v = "2.0"

拼接好的字符串如下：
3ea815c1a0aeb73bc7fabe63d104e451app_key23333126methodalibaba.aliqin.fc.sms.num.sendrec_num15831687958sign_methodmd5sms_free_sign_name身份验证sms_param{"code":"1234","product":"博览天下网"}sms_template_codeSMS_6740688sms_typenormaltimestamp2016-04-07 23:36:11v2.03ea815c1a0aeb73bc7fabe63d104e451

utf-8处理后，准备用md5加密前的如下：
3ea815c1a0aeb73bc7fabe63d104e451app_key23333126methodalibaba.aliqin.fc.sms.num.sendrec_num15831687958sign_methodmd5sms_free_sign_name%E8%BA%AB%E4%BB%BD%E9%AA%8C%E8%AF%81sms_param{"code":"1234","product":"%E5%8D%9A%E8%A7%88%E5%A4%A9%E4%B8%8B%E7%BD%91"}sms_template_codeSMS_6740688sms_typenormaltimestamp2016-04-07 23:36:11v2.03ea815c1a0aeb73bc7fabe63d104e451

md5加密后的如下：
DAC745A85D0CF1D325D745BB27B3A096

最后形成的url，做了utf-8处理后如下：
http://gw.api.taobao.com/router/rest?sig...{"code":"1234","product":"%E5%8D%9A%E8%A7%88%E5%A4%A9%E4%B8%8B%E7%BD%91"}&sms_template_code=SMS_6740688&sms_type=normal×tamp=2016-04-07 23:36:11&v=2.0

但提交后阿里大鱼xml报错如下：

25
Invalid signature
11igcz5j9mekq

看来以上的处理是不正确的，那么请问是哪一步错了，请segmentfault的大大支招，感激涕零