verify and publish do not use generic YAMF hashes

[adzialocha]

While decode and encode accepts any YAMF hash format, the methods verify and publish seem to be hard-coded to only support the BLAKE2b case:

1. https://github.com/pietgeursen/bamboo-rs/blob/master/bamboo-core/src/entry/publish.rs#L26
2. https://github.com/pietgeursen/bamboo-rs/blob/master/bamboo-core/src/entry/verify.rs#L137-L139

I'm not sure if publish and verify are meant to be opinionated implementations against the more low-level methods of the library, but wanted to bring up that they could also be made more generic to support all YAMF formats?

[pietgeursen]

Yeah, good point.

I'm not sure if publish and verify are meant to be opinionated implementations against the more low-level methods of the library

Nah, not really. I think it's just me being lazy because there's only one yamf-hash type at the moment.
Let's see if we can fix this when we pull out the YamfHash stuff in #18

[pietgeursen]

More thoughts:

What are the use cases?

• 1. You want to start a new feed and want to specify what the hash type should be
  • Seems legit
• 2. You want to publish to an existing feed but want to change your hash type?
  • Seems possible but rare. If it's even allowed to happen according to the spec?
• 3. verify should handle all the yamf hash variants, even if they've changed types in a single feed.
  • Is important but doesn't require making verify generic, you just pass it the previous entries and it takes care to decode the hashes correctly.

[pietgeursen]

Also, you can't make something generic over a variant of an enum.

So publish can't be made to be generic over variants of YamfHash.

But I'm sure we can satisfy the use-cases we want, just not with generics.

[pietgeursen]

To revisit this:

Current state:

• p2panda would like to use blake3 hashes because they're shorter
• a yamfhash design goal is to only add new hashes when existing ones break
  • there are two old open PRs requesting new hash types which Aljoscha doesn't want to merge.
• I want bamboo to work with multiple hash types (and pub key types too eventually).

Some possible ways forward:

• fork the yamf-hash spec into https://github.com/bamboo-rs and add blake3
  • might annoy @AljoschaMeyer 👎
  • yamf-hash is starting to be yet another multiformat which seems redundant 👎 . But it's in the name so 👍
  • easy to do 👍 👍 👍
  • would be compatible with existing bamboo entries 👍
  • Implementing it in yamf-hash is pretty much done 👍
• change bamboo to use multihash
  • I haven't worked how hard it's going to be to work that crate into bamboo ❓
  • would require forking the bamboo spec too
  • we get lots of hash types out of the box 👍
  • someone else maintains that code 👍
  • breaking change to existing bamboo entries 👎
• make bamboo be generic over the hasher by defining a trait that could be implemented for yamf-hash or other hash types
  • lets the consumer of the library decide which hashing scheme they want to use: 👍
  • quite a lot of work 👎
  • will make the api of bamboo harder to work with (gut feeling) 👎
  • breaking change to existing bamboo entries 👎

[cafca]

I don't care about existing bamboo entries and I don't know of anybody who does (yet) :D

Anyway, my guess is that

fork the yamf-hash spec into https://github.com/bamboo-rs and add blake3

is the least controversial and most pragmatic option because it wouldn't require changing the original YAMF spec.