Upgrade to v0.4.0

[TakodaS]

Description

Updated arkworks-rs dependencies to v0.4.0.

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Before we can merge this PR, please make sure that all the following items have been checked off. If any of the checklist items are not applicable, please leave them but write a little note why.

• [x] Targeted PR against correct branch (master)
• [x] Linked to Github issue with discussion and accepted design OR have an explanation in the PR that describes this work.
• [x] Wrote unit tests (Not needed as no new functionality was added).
• [x] Updated relevant documentation in the code
• [x] Added a relevant changelog entry to the Pending section in CHANGELOG.md
• [x] Re-reviewed Files changed in the Github PR explorer

[TakodaS]

@Pratyush Should I bother implementing CryptographicSponge for the Fiat-Shamir hash function found in rng or should I rip this all out in favour of Poseidon?

Edit: I see something similar is already in PR. Maybe I can commandeer that PR. I will go talk to @vlopes11.

[TakodaS]

@Pratyush Should I bother implementing CryptographicSponge for the Fiat-Shamir hash function found in rng or should I rip this all out in favour of Poseidon?

Edit: I see something similar is already in PR. Maybe I can commandeer that PR. I will go talk to @vlopes11.

Implementing FS hashing using the PoseidonSponge, temporarily with the same default initialization as used in the tests for crypto-primitives.

[autquis]

Any updates on this? I am ready to take any necessary steps to make it ready to merge. @Pratyush @mmagician

[TakodaS]

Any updates on this? I am ready to take any necessary steps to make it ready to merge. @Pratyush @mmagician

Go right ahead! I guess you can make a new pull request and I will close this one?