Replace the placeholder route_tag with a deterministic keyed route identifier

[mikewheeleer]

Implement a deterministic route identifier

Description

route_tag in src/lib.rs is documented as a placeholder "used by the backend to verify route integrity," but it simply echoes its (source, destination) arguments back unchanged — it ignores the env, performs no hashing, and offers no integrity value whatsoever. Its only test asserts the echo. This issue replaces it with a real deterministic route identifier the backend can use to correlate on-chain routes with off-chain records.

Requirements and context

• Repository scope: StableRoute-Org/Stableroute-contracts only.
• Implement route_tag(env, source, destination) -> BytesN<32> as a deterministic hash over (source, destination) using env.crypto() (e.g. keccak256/sha256 of the encoded symbols).
• Make the tag direction-sensitive so USDC→EURC and EURC→USDC differ (matching the directional pair model).
• Optionally include the tag in the route event payload so indexers can key on it (note this is additive and document the payload change).
• Reject identical source/destination consistent with register_pair semantics, or document why echo-of-identity is acceptable.

Suggested execution

• Fork the repo and create a branch
• git checkout -b feature/contracts-35-deterministic-route-tag
• Implement changes
  • Write code in: src/lib.rs — hashed route_tag implementation.
  • Write comprehensive tests in: src/lib.rs #[cfg(test)] mod test — assert determinism (same input → same tag), direction sensitivity, and distinct tags for distinct pairs.
  • Add documentation: document the route-identifier scheme in README.md.
  • Include NatSpec-style doc comments (///) on the changed entrypoint.
  • Validate security assumptions: tag is collision-resistant for the symbol domain; no preimage leak of secrets.
• Test and commit

Test and commit

• Run cargo fmt --all -- --check, cargo build, and cargo test.
• Cover edge cases and failure paths: determinism, direction flip, two different pairs, repeated calls.
• Include the full cargo test output and a short security notes section in the PR description (threat model + mitigations).

Example commit message

feat: replace placeholder route_tag with deterministic keyed identifier

Guidelines

• Minimum 95 percent test coverage for impacted modules.
• Clear, reviewer-focused documentation.
• Timeframe: 96 hours.

Community & contribution rewards

• 💬 Join the StableRoute community on Discord for questions, reviews, and faster merges: https://discord.gg/37aCpusvx
• ⭐ This is a GrantFox OSS / Official Campaign task and may be rewarded. When your PR is merged you'll be prompted to rate the project — if this issue and the maintainers helped you ship, we'd be grateful for a 5-star rating. Clear questions in Discord and tidy, well-tested PRs are the fastest path to a merge and a reward.

[Baskarayelu]

I’d love to be assigned this issue and contribute across the relevant areas, whether it involves smart contracts, UI development, backend logic, design implementation, or overall system integration. I’m comfortable working across the full stack and can adapt to the project’s technical requirements to ensure a smooth and consistent contribution.