How to restrict access to a game web application?

Question

Game development

Dear habralyudi!
At my leisure, as a hobby, I took up the development of interactive educational simulators in the form of web applications, so that the child would not bother to go to the address, and immediately started classes. I do not publish links, fearing a habraeffect, because hosting is still weak.
So, I faced a question, I decided to look for help in resolving it on Habré.
To begin with, an introductory one: the same child can study completely freely from several different devices, with dynamic IPs. At the same time, several different children can freely study from the same device, to the point that they are not even relatives, for example, at school. Moreover, they can change each other completely arbitrarily and unpredictably, for example, in a fit of excitement, forgetting to change their account, i.e. it is not at all excluded that someone will "spoil" or, conversely, "improve" statistics on someone else's account. And such cases should be, if not eliminated, then at least minimized.
At the same time, in order to achieve the learning goals, each child must be identified unambiguously. The situation is further complicated by the fact that typical login-password-pin authentication is completely optional, which will work on the fly.
It is necessary to identify each child so that the intellectual system can select tasks strictly individually for each child. Now the pseudo-random generator operates in the prototype, and its effectiveness is not even half, alas.
It is clear that parents will also be involved somewhere. But independent studies are not excluded at all.
Those. it is obvious that the identification of a particular student must be multi-stage. The solution, as I see it, lies somewhere in the field of behavior and interface analysis. Of course, ordinary authentication and the session mechanism will also participate, but by themselves, they will not solve this issue.

Answer 1

"absolutely unambiguous" identification by behavior analysis - the task in terms of scale pulls on a good scientific study.
If we are talking about preschoolers / younger students, I would suggest the same PIN, but made not in the form of numbers, but in the form of pictures.
Choose your avatar, a couple of colors for the avatar parts, and some accessory. In this way, several thousand variants can be organized.
If you use this, in conjunction with IP and cookie bindings, you can get quite good accuracy. But by no means a guarantee.

Answer 2

When the same child is engaged from different devices, he can be identified by his PIN. No problem. The form of organization of the pin is debatable.
But when different children are engaged on the same device ... Here the dog rummaged.
I emphasize that each decision of the child is logged in relation to the task, in order to identify which tasks cause difficulties for him, because. these tasks need to be emphasized. If the child is alone behind the device, there are no questions. But if there is more than one of them in a family or class, then a problem arises. Children can spoil or improve each other's statistics, which should not happen.
And then the problem with the collective solution of problems came to mind. I still don't understand how to stop it.