How to check the accuracy of the data?

Question

Electronic digital signature

Let's say we have two servers A and B. A client visits server A and receives, say, 64 bytes of some data. then the client goes to server B and gives him these 64 bytes.
It is not known in advance which bytes server A will give. Server B cannot query Server A. Server A and Server B cannot know anything about clients (they cannot register and log in).
Question: how can server B determine that these 64 bytes are received from server A?
There is an idea, in addition to bytes, to transfer some kind of crypto-resistant signature. Plz tell me what would you use?