How to find the key to encrypt text to encryption?

[matija_]

Hello, I have a date with format (dd.mm.yy) and that value represents the code ID.

I want to find the algorithm and a key so I can produce the code for the future dates.

Table of solved solutions looks like this below: (last characters in day ID are censored XX)

day ID      Day (dd.mm.yy)
891383XX 25.01.21
6018EFXX 23.02.21
A38F43XX 25.02.21
2A31ADXX 03.03.21

How should I approach the problem solution?

[atom]

Well no matter if it's a hash or a cipher, hitting it would be pure luck, but is very unlikely. The right way to do is to understand the process which produces that output.

[matija_]

Well no matter if it's a hash or a cipher, hitting it would be pure luck, but is very unlikely. The right way to do is to understand the process which produces that output.

That makes sense, but the process in hidden, because it is a pub** machine.