Is Seraphis keeping the 10-block lock? I know it has TX chaining, I just haven't heard about the lock.

It doesn't sound decided yet

There have been some proposals: monero-project/research-lab #95 but AFAIK the plan is to stick with it for now.

UkoeHB: Does your Seraphis library support pruning? How much work would it be to make tx_extra prunable? i.e. being able to calculate the txid without tx_extra (only knowing its hash).

tevador: I didn’t define a pruned tx type but it should be easy enough

I think the tx is depends on tx extra though

tx id

It’s part of a tx proposal which is one component of the tx hash

Since you need to sign on the tx extra

Signing just the hash should be equally secure.

The tx proposal hash could be refactored as a merkle tree

I’m a little skeptical about pruning tx extra, since presumably it’s data that the recipients of a tx need.

Pruning is currently only about removing proof artifacts by assuming you won’t need to re-check signatures.

IMO designing the protocol in a way that allows more pruning to be done later is beneficial. If possible, everything that's hashed should be a Merkle tree.

Doing more hashes does increase the cost of computing a tx id

logarithmically

Right now it’s 4 hashes to get an id

in any case, tx_extra is the only parts that has a potentially unbounded size

so that 1 extra hash might be worth it

Yeah. I suppose selective pruning of tx extras could be quite desirable for many node operators. Perhaps ironically, the tx extra is a vector for censorship.

Why are key images hashed twice when calculating the txid?

To commit to the set of key images?

yeah input images are not available when making a tx proposal, only the key images, so input images need to be fully hashed separated for the tx id

actually maybe they are available hmm

My goal was to decouple the signed message from the details of input images so modifying an input image structure doesn't mean you need to re-implement the message. It also more concisely encapsulates what you want to commit to with a tx proposal.