Feat: add tests to check slh-dsa key gen from seed

[manel1874]

Forgot to comment on the previous PR that maybe we should add some tests for this.

How to run those from liboqs main folder:

cd build
ninja sig_keypair_from_seed
./tests/sig_keypair_from_seed

[greptile-apps]

Greptile Summary

This PR extends the existing sig_keypair_from_seed test to cover all 12 SLH-DSA PURE variants (SHA2 and SHAKE, across 128/192/256 security levels). The main changes are:

• Added get_seed_length() helper that maps algorithm names to the correct SLH-DSA seed length (3 * n bytes: 48 for 128-bit, 72 for 192-bit, 96 for 256-bit), falling back to 32 bytes for Falcon and ML-DSA.
• Updated seed buffer from fixed 32-byte SEED_LENGTH to 96-byte MAX_SEED_LENGTH to accommodate the largest SLH-DSA seed.
• Renamed falcon_algorithms to algorithms and added all 12 SLH-DSA PURE entries to the test list.
• Updated printf format specifier from %u to %zu to match the size_t type of the new seed_len variable.

The algorithm names match the identifiers defined in src/sig/sig.h, and the seed lengths align with the validation logic in each SLH-DSA keypair_from_seed implementation (which enforces seed_len == 3 * prm->n).

Confidence Score: 4/5

• This PR is safe to merge — it only adds test coverage with no changes to library source code.
• The PR is test-only and makes straightforward, correct changes. Algorithm names match the library's identifiers, seed lengths are consistent with the SLH-DSA implementation's validation, and the buffer sizing is adequate. The only finding is a stale comment, which is cosmetic.
• No files require special attention

Important Files Changed

Filename	Overview
tests/sig_keypair_from_seed.c	Extends keypair-from-seed determinism tests to cover all 12 SLH-DSA PURE variants. Adds a get_seed_length() helper to compute the correct seed sizes (48/72/96 bytes) based on the algorithm's security level. Algorithm names, seed lengths, and array sizing are all correct. One stale comment remains from the pre-SLH-DSA version.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[main] --> B[Loop over algorithms array]
    B --> C{Algorithm type?}
    C -->|Falcon-512/1024| D[get_seed_length → 32 bytes]
    C -->|ML-DSA-44/65/87| D
    C -->|SLH_DSA_*_128*| E[get_seed_length → 48 bytes]
    C -->|SLH_DSA_*_192*| F[get_seed_length → 72 bytes]
    C -->|SLH_DSA_*_256*| G[get_seed_length → 96 bytes]
    D --> H[test_keypair_from_seed_twice]
    E --> H
    F --> H
    G --> H
    H --> I[Generate seed with KAT PRNG]
    I --> J[First keypair_from_seed call]
    J --> K[Second keypair_from_seed call]
    K --> L{Keys match?}
    L -->|Yes| M[SUCCESS]
    L -->|No| N[FAILURE]

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_{Last reviewed commit: b8fe899}

[greptile-apps]

_{1 file reviewed, 1 comment}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

Stale comment after rename
This comment still says "Test each Falcon variant (Falcon-512 and Falcon-padded-512)" but the loop now iterates over all supported algorithms including ML-DSA and SLH-DSA variants. The comment should be updated to reflect the broader scope.

Suggested change

	// Test each Falcon variant (Falcon-512 and Falcon-padded-512)
	// Test each algorithm variant