Multi-site Single sign-on scheme!

The new task has just been taken, the head is a bit big!
There are currently 4 sites, the discuz,b used by a with wordpress,c and D are independently developed projects,
4 sites have a certain amount of users, now need to integrate single sign-on, the four sites are on the ground to continue to access in, so the current integration feel a bit difficult.
In the case of Ucenter without the help of Discuz, is there any plan to refer to it?

If a user in the B station and C station respectively registered users, are the same email account, at this time want to log on D station, how to do?

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The new task has just been taken, the head is a bit big!
There are currently 4 sites, the discuz,b used by a with wordpress,c and D are independently developed projects,
4 sites have a certain amount of users, now need to integrate single sign-on, the four sites are on the ground to continue to access in, so the current integration feel a bit difficult.
In the case of Ucenter without the help of Discuz, is there any plan to refer to it?

If a user in the B station and C station respectively registered users, are the same email account, at this time want to log on D station, how to do?

Ucenter is the best solution, not one of them.
Of course, if they are under the same domain name, sharing cookie_id with the parent domain is also possible.

A website provides OAuth2.0
Other sites are unified with the third party landing on site A.

Does this kind of thinking not know whether it is feasible?
First set up a new user table, specifically for your 4 site user table, and then query the time to check the table there are no users, some words directly login, if not, go to your 4 sub-station one by one query, find out after the user's information written to this new users table, of course, You can also use a script background directly to the 4 sub-station user table all the time into the table. Personal opinion, for reference only:)

To consider the user password encryption method of each system;
You only have to integrate all of the system's member data before you can do single sign-on

Your entire membership management system. All station logins go to this system to invoke API interface.

For reference.

Ucenter is not a member management system??? Why Step on-_-... Please advise?

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