feat: Make public inputs the start of the UH and MH proof

[lucasxia01]

Closes AztecProtocol/barretenberg#1089.

Removes the circuitSize, numPublicInputs, and pubInputsOffset metadata from the proof. The result is that the public inputs are at the beginning of the proof.

Followup work includes:

• Medium: making these metadata actual witnesses in the recursive VK (Should circuit_size, etc.. be witnesses in Recursive VerificationKey? barretenberg#983).
• Small: fixing verify_honk_proof acir test inputs (Fix verify_honk_proof input generation barretenberg#1279).
• Small: cleaning up or removing the proof surgeon.
• Medium: Further structuring the proof/public inputs output as Cody suggests in Move public inputs to the front of proof barretenberg#1089 to split out the accumulators in the pub inputs.
• Small Adding pubInputsOffset to the Honk Solidity VK (Add pubInputsOffset to Solidity Honk VK barretenberg#1281).

[Maddiaa0]

Question, if there is no offset anymore can it just be removed? What was it for ?

[lucasxia01]

Question, if there is no offset anymore can it just be removed? What was it for ?

No its still there in the vk, just not redundantly in the proof. The pub_inputs_offset basically represents the number of ecc_ops. I'm not sure if it needs to exist anymore if we don't use MegaHonk with an unstructured trace.

[lucasxia01]

Will #11024 eventually be handled by your series of works?

@codygunton yep, Saleel brought that up as well and that's on my radar as a followup in the immediate future.

[ihyunnam]

For UltraHonk used as Noir backend, where can the verifier retrieve public inputs? It seems like previous discussions are saying the proof now begins with public inputs (with no metadata before them), but when I actually print out an UltraHonk proof that I'm using with Noir, the first 4 bytes seem to be metadata and public input bytes are not found anywhere in the proof. bb --version returns 0.82.2 and verify prints Scheme is: ultra_honk.

FYI, I'm using the following bbup commands.

bb prove -b /workspace/target/hello_world.json -w /workspace/target/hello_world.gz -o /workspace/target/proof
bb write_vk -b /workspace/target/hello_world.json -o /workspace/target/vk
bb verify -k /workspace/target/vk -p /workspace/target/proof

[saleel]

@ihyunnam Public inputs are after the 4 bytes of metadata - 32 bytes each.

FYI this will get even better once #12816 is merged in, after which the proof and public inputs are saved as separate files.

[lucasxia01]

Hi Ihyun :)

You're right that there's 4 bytes of metadata that exist at the beginning of the proof, which are used for deserialization. The public inputs in the current release of bb should exist right after those 4 bytes, in 32 byte chunks.