ZKP tie the proof to any data vs metadata

Zama TFHE-rs
1

I want understand the code on the following page on ZKP,

I wanted to understand what tie to any data means as a function of metadata. To be more precise,
what would be the difference between setting metadata= vs the metadata given in the code?

Thanks very much.

2

Hi!
For the sake of brevity the example does not show it, but the idea is that the metadata is computed separately on the client and the server. The proof is always rejected if the metadata does not match.

For example, if the proven ciphertext is a blockchain transaction input, you can use it make sure that a proof is only used for a single transaction.