ML-DSA

ML-DSA (NIST FIPS 204) digital signature API. Header: pkc/mldsa/noxtls_mldsa.h.

Purpose

Use ML-DSA for post-quantum signatures in standalone PKC workflows and TLS 1.3 CertificateVerify paths.

Enablement

• Build flag: -DNOXTLS_CFG_FEATURE_ML_DSA=ON
• Dependency: NOXTLS_FEATURE_PKC must be enabled (validated by noxtls_check_config.h)

Parameters and sizes

Parameter	Public key	Secret key	Signature
NOXTLS_MLDSA_44	1312	2560	2420
NOXTLS_MLDSA_65	1952	4032	3309
NOXTLS_MLDSA_87	2592	4896	4627

Maximum compile-time contracts:

• NOXTLS_MLDSA_MAX_PUBLIC_KEY_LEN = 2592
• NOXTLS_MLDSA_MAX_SECRET_KEY_LEN = 4896
• NOXTLS_MLDSA_MAX_SIGNATURE_LEN = 4627
• NOXTLS_MLDSA_SEED_LEN = 32
• NOXTLS_MLDSA_RND_LEN = 32
• NOXTLS_MLDSA_MAX_CONTEXT_LEN = 255

Key APIs

noxtls_mldsa_public_key_len

uint32_t noxtls_mldsa_public_key_len(noxtls_mldsa_param_t param);

Return the exact public-key length for a parameter set.

noxtls_mldsa_secret_key_len

uint32_t noxtls_mldsa_secret_key_len(noxtls_mldsa_param_t param);

Return the exact secret-key length for a parameter set.

noxtls_mldsa_signature_len

uint32_t noxtls_mldsa_signature_len(noxtls_mldsa_param_t param);

Return the exact signature length for a parameter set.

noxtls_mldsa_keygen

noxtls_return_t noxtls_mldsa_keygen(noxtls_mldsa_param_t param,
                                    uint8_t *public_key,
                                    uint8_t *secret_key);

Generate ML-DSA keypair.

noxtls_mldsa_sign

noxtls_return_t noxtls_mldsa_sign(noxtls_mldsa_param_t param,
                                  const uint8_t *secret_key,
                                  const uint8_t *message,
                                  uint32_t message_len,
                                  uint8_t *signature,
                                  uint32_t *signature_len);

Sign message bytes. signature_len is in/out (input capacity, output actual size).

noxtls_mldsa_verify

noxtls_return_t noxtls_mldsa_verify(noxtls_mldsa_param_t param,
                                    const uint8_t *public_key,
                                    const uint8_t *message,
                                    uint32_t message_len,
                                    const uint8_t *signature,
                                    uint32_t signature_len);

Verify an ML-DSA signature.

Test/vector hooks

void noxtls_mldsa_set_test_seed_sequence(const uint8_t *bytes, uint32_t byte_len);
void noxtls_mldsa_set_test_signing_overrides(const uint8_t *pre,
                                             uint32_t pre_len,
                                             const uint8_t *rnd,
                                             uint32_t rnd_len,
                                             uint8_t externalmu);

Deterministic hooks used by test and vector-conformance harnesses.

Typical flow

1. Select NOXTLS_MLDSA_44, 65, or 87.
2. Query sizes using noxtls_mldsa_*_len.
3. Allocate key/signature buffers.
4. Call noxtls_mldsa_keygen.
5. Sign with noxtls_mldsa_sign.
6. Verify with noxtls_mldsa_verify.

TLS and X.509 integration

• TLS 1.3 CertificateVerify support and signature scheme IDs: TLS 1.3 PQC
• X.509 parse/verify handling for ML-DSA OIDs: Certificates

Security notes

• ML-DSA signature IDs currently use private-use code points for prototyping and may change when standardized IDs are available.
• Always validate signature_len against noxtls_mldsa_signature_len(param).
• Treat private keys and transient randomness/seed buffers as sensitive material.