How to extract the poseidon hash used by EZKL

[tpmmthomas]

Hi there, I am trying to use EZKL and I want to extract the way it computes the hash for the output.

I know that if I set the output visibility to "hashed", it will give me a poseidon hash of the output in the proof file. I want to be able to recompute this without using the ZKP circuit.

I have identified the file src/circuit/modules/poseidon/poseidon_params.rs for the poseidon hash params and a library https://github.com/ingonyama-zk/poseidon-hash that implements poseidon hash independently.

However I can't seem to match all the params. From the blog post by EZKL devs (https://hackmd.io/@letargicus/SJOvx48Nn) I have identified these params
security_level = 128 alpha = 5 input_rate = 4 t = 4 full_round=8 partial_round=56

However in the poseidon_params.rs file, the MDS is 2x2 which does not match the dimension required (4x4) of the python library.

What am I missing? Thank you so much!!