Facebook cuid variable decoding

Anybody have idea how cuid variable is hashed/encoded?
https://www.facebook.com/profile/pic.php?cuid=
Sample variables:

Code:

AYgR87rXaOJ_x_o32LrY9_wt1fnm6yhndKPGgoUcmHROoXroLEFrihdAJkhEQhIyioBBBFWakjSYC8FoNBHHxbXSrvYNob6csqdth6U19_hbepcyfpwjFjie9-WsVx0LMBaDjCcIhvSh8XB9SNpHi4OC

Code:

AYj5Tjg95jUWOWrHWuItDo_sXGOAigbuRG0rdjKZlAXtYVjqzrvCWcxuGQfEsIVGjOgzjFXWkdrc7DaLDTc41V7CWpoJNlQVYYMM3PzSs5Ng5M7kflmjcPILZdCB6oZ3oUQrt2vvqAC3mVRCQcHPW9gw

Code:

AYhJDv2ziv8lSmNc4QdK50DABt8_4xnQ3HjyxMvpMu-6Bbld1fAodg14KCqAQxXQdo1iPdRjOLuzgoDlpIb6bQ6sYVzlofc1mKVGUg6PfZiS_AZr0i_2vB2n0EDHKdvG_zmHpk8_hpvuawpuoD1xeESv

Code:

AYh4ZOBf0FOtq0id6QBZ-cA6Fi4q5fJ4zcy3Hs99eV8lcfrMlME4SSgh3A9eaXaTiLXC5PC-F_NA9AyBJM0fwYat9XZRbvRpCMTJxlszGoCv76UlcBKM3xsKwbyWdK0YyRYcRyXyYWmjBa7ngIvDl3yz

The strings is separating in this forum but they are jointly
thanks in advance

 

It looks like Base64-algorithm, see more - http://en.wikipedia.org/wiki/Base64

 

base64 do not have special chars like "_" or "-".
Any other idea?

 

then decode this

 

then decode this

 

This is comercial forum?
This is only encoding,not reverse engineering....

 

This is "base64url".Thanks.

 

Dude, it could be modified b64, for example "A" character is replaced by "_" or something like this.

 

Yes bro.

 

http://www.xtmotion.co.uk/facebook-to-encrypt-user-ids/
http://developers.facebook.com/docs/howtos/login/signed-request/
http://qugstart.com/blog/ruby-and-rails/facebook-base64-url-decode-for-signed_request/
This is more than only base 64 for url.
Any hints/ideas?

Here is sample string:
http://pastebin.com/rVcMav03