Greetings from the miniBB author.
fa3d:
Where should I put the code to unencrypt those values? (all user fields are encrypted). Any ideas?
It's a question not related to miniBB software, in general. How could we know what happens in your database?
If you have no documentation for your website, you'd need to hire a
clairvoyant. Before synchronizing miniBB, you should fully understand/know
at first,
how your website works, not miniBB.
As about synchronizing miniBB, you could check
this solution first; specially, pay attention at the section claiming required fields for miniBB. And when adjusting the login routine, mostly you should take a look in bb_cookie.php and bb_func_login.php. You need to make these scripts to set the cookie which look exactly the same like the cookie from your root website. All in all, if you will go the solution step by step, you will most likely find a solution for your own forum.
Seeing the data you have, it has 32 chars in length and looks very similar to MD5 hash, which can't be (easily) decoded. So I'm not sure what kind of decoding function do you have. Most likely you should
compare these values by the incoming input, which should be also encoded on the fly.
Also, it seems your website is using email address as login. This is invalid approach for minBB. MiniBB forum members should have a common username, which is shown to all guests and other members as the author of the post. You must agree you can't use email address visible to all, so you should extend your website to have a static username, which then could be plugged in miniBB.
Let me know if this helped or if you will need other kind of help.