Sign Method
Concatenate app_key, time, app_secret in turn, and do sha1() .
Example
app_key = mBOMg20QW11BbtyH4Zh0
time = 1647847498
app_secret = V6aRfxlPJwN3ViJSIFSCdxPvneajuJsh
sign = sha1(mBOMg20QW11BbtyH4Zh01647847498V6aRfxlPJwN3ViJSIFSCdxPvneajuJsh)
= 7293d385b9225b3c3f232b76ba97255d0e21063e