Change jubjub and poseidon backend from Dusk to MidnightZK

[damrobi]

Content

Change the backend used for the Jubjub curve and Poseidon hash function from the Dusk implementation to the newly released Midnight crates.

Pre-submit checklist

• Branch
  • Tests are provided
  • Crates versions are updated
  • CHANGELOG file is updated
  • Commit sequence broadly makes sense
  • Key commits have useful messages
• PR
  • All check jobs of the CI have succeeded
  • Self-reviewed the diff
  • Useful pull request description
  • Reviewer requested
• Documentation
  • No new TODOs introduced

Comments

Issue(s)

Relates to #2888

[github-actions]

Test Results

    4 files  ±0    169 suites  ±0   22m 22s ⏱️ +17s
2 317 tests ±0  2 317 ✅ ±0  0 💤 ±0  0 ❌ ±0 
7 296 runs  ±0  7 296 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 34e95e8. ± Comparison against base commit 1e052e6.

♻️ This comment has been updated with latest results.

[Copilot]

Pull request overview

This pull request migrates the cryptographic backend for Jubjub curve operations and Poseidon hash functions from Dusk Network's implementation (dusk-jubjub, dusk-poseidon) to Input Output's Midnight implementation (midnight-circuits, midnight-curves). This represents a significant change in the underlying cryptographic dependencies for the Schnorr signature scheme.

Key Changes

• Replaced Dusk cryptographic libraries with Midnight equivalents (versions 6.0.0 and 0.2.0)
• Updated Poseidon hash to return BaseFieldElement instead of ScalarFieldElement with type conversion added for signature operations
• Implemented SHA256 pre-hashing for hash-to-curve operations using the Midnight HashToCurveGadget
• Updated all golden test values to reflect the new backend's outputs

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
mithril-stm/Cargo.toml	Replaced dusk dependencies with midnight-circuits and midnight-curves; added sha2 dependency
Cargo.lock	Updated dependency tree with new midnight crates and their transitive dependencies
mithril-stm/src/signature_scheme/schnorr_signature/jubjub/poseidon_digest.rs	Migrated from Dusk's Hash::digest_truncated to Midnight's PoseidonChip::hash; changed return type to BaseFieldElement
mithril-stm/src/signature_scheme/schnorr_signature/jubjub/field_elements.rs	Added BaseFieldElement serialization methods, from_raw and from_base_field conversion methods for ScalarFieldElement
mithril-stm/src/signature_scheme/schnorr_signature/jubjub/curve_points.rs	Replaced Dusk's hash_to_point with Midnight's HashToCurveGadget using SHA256 pre-hashing; updated type aliases
mithril-stm/src/signature_scheme/schnorr_signature/signature.rs	Changed challenge field type from ScalarFieldElement to BaseFieldElement; added type conversion in verification
mithril-stm/src/signature_scheme/schnorr_signature/signing_key.rs	Updated to use new Poseidon digest function and added BaseFieldElement to ScalarFieldElement conversion
mithril-stm/src/signature_scheme/schnorr_signature/verification_key.rs	Reordered imports to follow Rust conventions
mithril-stm/src/signature_scheme/schnorr_signature/error.rs	Added BaseFieldElementSerialization error variant
mithril-stm/src/signature_scheme/schnorr_signature/jubjub/mod.rs	Added serde implementation for BaseFieldElement
mithril-stm/benches/schnorr_sig.rs	Updated benchmark names and implementation to use Midnight's PoseidonChip

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[hjeljeli32]

LGTM ✅
I left 3 small non-blocking comments.

[jpraynaud]

LGTM

[curiecrypt]

LGTM 👍