Handling incorrect mint time

[thesimplekid]

Currently in NUT-06 we optionally return the mint time (https://github.com/cashubtc/nuts/blob/main/06.md). We added this to the spec because a mint using an incorrect time could lead to the spending condition path being allowed when it shouldn't or the reverse. However, we do not define that this time must be correct or within some tolerance.

When I added this to the cdk wallet I put in a check that the returned time was within 30 seconds without much thought, but it seems this is causing issues with some mints that are returning delayed times (cashubtc/cdk#1194) reported up to 20 minutes off.

Since there isn't a tolerance in the spec, I guess cdk shouldn't be doing this check however I think it's an important check for spending conditions. Should we add a tolerance to the spec? I guess then it becomes a question of who has the correct time.

[SatsAndSports]

My latest update, I think 21mint is doing caching:

First, all mints are synced with each other and with my laptop here:

$ date +%s ; for mint in https://21mint.me https://mint.minibits.cash/Bitcoin https://testnut.cashu.space https://8333.space:3338  https://nofees.testnut.cashu.space https://mint.coinos.io; do curl -s $mint/v1/info | jq .time | tr -d '\n'; echo " ${mint}" ; done
1760708875
1760708875 https://21mint.me
1760708876 https://mint.minibits.cash/Bitcoin
1760708876 https://testnut.cashu.space
1760708876 https://8333.space:3338
1760708876 https://nofees.testnut.cashu.space
1760708877 https://mint.coinos.io

But then, I ran the same command multiple times in the following seconds. See that 21mint is not updating

$ date +%s ; for mint in https://21mint.me https://mint.minibits.cash/Bitcoin https://testnut.cashu.space https://8333.space:3338  https://nofees.testnut.cashu.space https://mint.coinos.io; do curl -s $mint/v1/info | jq .time | tr -d '\n'; echo " ${mint}" ; done
1760708984
1760708875 https://21mint.me
1760708985 https://mint.minibits.cash/Bitcoin
1760708985 https://testnut.cashu.space
1760708985 https://8333.space:3338
1760708986 https://nofees.testnut.cashu.space
1760708986 https://mint.coinos.io

Here there is 80 seconds of difference:

$ date +%s ; for mint in https://21mint.me https://mint.minibits.cash/Bitcoin https://testnut.cashu.space https://8333.space:3338  https://nofees.testnut.cashu.space https://mint.coinos.io; do curl -s $mint/v1/info | jq .time | tr -d '\n'; echo " ${mint}" ; done
1760709061
1760708875 https://21mint.me
1760709062 https://mint.minibits.cash/Bitcoin
1760709062 https://testnut.cashu.space
1760709062 https://8333.space:3338
1760709063 https://nofees.testnut.cashu.space
1760709063 https://mint.coinos.io

[SatsAndSports]

My coding agent thinks CDK is caching it:

Read(crates/cdk/src/wallet/mod.rs)
  ⎿  Read 30 lines (ctrl+o to expand)

● Ah! I see it now - line 319-321:

  self.localstore
      .add_mint(self.mint_url.clone(), Some(mint_info.clone()))
      .await?;

  The mint info IS being saved to local storage! This might mean subsequent calls could potentially use cached data. Let me check the add_mint implementation: