[zachyking]

main's supply-chain job fails since about 2026-10-24 on RUSTSEC-2026-0387: timing variability in crypto-bigint operations intended to be constant-time. The fix is crypto-bigint >= 0.7.6.

Facts (lead-verified on origin/main 0f610bb):

• cargo tree -i crypto-bigint -e normal --workspace --all-features shows crypto-bigint 0.5.5, via elliptic-curve 0.13.8, used by ecdsa 0.16.9, p256 0.13.2, p384 0.13.1 and primeorder 0.13.6. All of these come from averin-decision-core, under the optional rfc3161 feature.
• Shipped uses are signature verification only: verify_ecdsa_p256 and verify_ecdsa_p384 in core/src/rfc3161.rs, which call VerifyingKey::from_sec1_bytes then verify or verify_prehash.
• The inputs are the pinned TSA public key, the token's signature and the signed attributes. All of them are public, so timing variability reveals nothing secret.
• P-256 and P-384 signing (make_test_token and similar) is compiled only under #[cfg(any(test, feature = "test-tsa"))]. Only CI enables test-tsa (cargo test --features test-tsa).
• No release in the 0.13 line depends on a fixed crypto-bigint. Fixing it means migrating to the RustCrypto 0.14 line (ecdsa 0.17, p256 0.14, p384 0.14). That is an API change in the verification path, too large for the release-1 window.

Change. One ignore entry in deny.toml with the reason written out. It follows the same pattern as the existing RUSTSEC-2023-0071 entry, which covers the verify-only rsa path. It includes a revisit date (2027-01-31) and the follow-up: migrate after release 1 and remove the entry.

Checks.

• cargo deny check advisories: advisories ok.
• Kit claims: 745 checks, 0 failures.
• Legacy check-claims.py: passes.

This unblocks averin#50 and every averin PR, whose supply-chain job inherits the failure from main.

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