Generating the req_token

Hello, I was trying my best to login to snapchat using their private API but with failed attempts. However, Now I've found one iOS application in appstore. That can login to snapchat successfully. I've Sniffed the traffic using Burpsuite. HTTP requests goes to a private server API. then it send requests to Snapchat API as Shows below: --------------------------------------------------------------- HTTP POST: POST /mainop/loginauth HTTP/1.1 Host: sc.*********.com Content-Type: application/x-www-form-urlencoded Connection: keep-alive Accept: */* User-Agent: ********/1.8 (iPad; iOS 9.3.1; Scale/2.00) Accept-Language: en-US;q=1, ar-US;q=0.9 Accept-Encoding: gzip, deflate Content-Length: 104 password=passtest&sign=89390375953fb95443f5411ebbcea87ce58e002f76dee1e6a3edddb3d401b9cc&username=mzaboss ------------------------------------------------- HTTP Response: HTTP/1.1 200 OK Date: Fri, 13 May 2016 19:13:59 GMT Server: Apache/2.4.7 (Ubuntu) X-Powered-By: PHP/5.5.9-1ubuntu4.14 Content-Type: application/json Content-Length: 1367 X-Cnection: close {"result":true,"message":"OK OK","data":{"endpoint":"https:\/\/[login to view URL]\/loq\/login","code":200,"headers":{"Accept":"*\/*","Accept-Language":"en","Accept-Locale":"en_US","User-Agent":"Snapchat\/9.26.0.1 (iPod7,1; iOS 8.4; gzip)","X-Snapchat-Client-Auth-Token":"v5:FC09E8B233F84D3406760FC2:39211320AF436A4ED7D7719F8305EEFEC4149D8BA37E45D42C23A24FE2CE87D3FD067AFACD8348E11EAEB6D07DDE21E3010897988047F7ED11B6EE0D941107E7173FBCAF073F44E2DDC6D7151723671660B911098406CCEF7AED0537978E0C6E654148185C8FAB9FCD1FAE8916061893C94A43E8A8BFA078AEED42FAF6CF7E42EEF503D6292BFB5EA3B12A5A164FC23F4E86","X-Snapchat-Client-Token":"v5:D3F899E30D9A8D08235B48E8:EA9955D26E294EBB9DA04B14963B864FF15CECE6B1FBC5CF9D06590223CCE2C73597F114ED61DB83DEFBCE1BDE7FC4D23E60D5D899EC048E9D23846AA708EF9C8C93FCBF6AAB178D80E185A165D944876DD632918A3E5C334C193227CB04B6A5A992E0","X-Snapchat-UUID":"0794F222-0187-4A70-B451-9A0C21D8DF1B"},"params":{"confirm_reactivation":"false","from_deeplink":"false","height":"1136","nt":"1","password":"passtest","pre_auth_token":"","remember_device":"true","req_token":"930ee855ba0116486ec7b5e4f0a644b4c9ed4d8819a91a8409b43414d4c51acb","screen_height_in":"3.5","screen_height_px":"568","screen_width_in":"1.9","screen_width_px":"320","timestamp":1463166839974,"username":"mzaboss","width":"640"},"settings":{"force_clear_headers":true,"force_clear_params":true}}} --------------------------------- So what I want is.. I'd like to know how the post requests generate an "Sign=" password=passtest&sign=89390375953fb95443f5411ebbcea87ce58e002f76dee1e6a3edddb3d401b9cc&username=mzaboss The point is I want to be able to send requests with auto generation Sign. I believe is something related with this one: [login to view URL] Skype: mzaboss Thank you, regards.