Adjust README to indicate support for HashML-DSA

Signed-off-by: Matthias J. Kannwischer <[email protected]>

Author: mkannwischer

README.md

@@ -85,15 +85,19 @@ By default, mldsa-native uses the "hedged" signing variant as specified in FIPS
 
 The deterministic variant can be enabled by undefining `MLD_RANDOMIZED_SIGNING`, but FIPS 204 warns that this should not be used on platforms where fault injection attacks and side-channel attacks are a concern, as the lack of fresh randomness makes fault attacks more difficult to mitigate.
 
-### Does mldsa-native support the pre-hash/digest sign/verify mode (external mu)?
+### Does mldsa-native support the external mu mode?
 
 Yes. mldsa-native supports external mu mode, which allows for pre-hashing of messages before signing. This addresses the pre-hashing capability described in the NIST PQC FAQ[^NIST_FAQ] and detailed in NIST's guidance on FIPS 204 Section 6[^NIST_FIPS204_SEC6].
 
 External mu mode enables applications to compute the message digest (mu) externally and provide it to the signing implementation, which is particularly useful for large messages or streaming applications where the entire message cannot be held in memory during signing.
 
 ### Does mldsa-native support HashML-DSA?
 
-No. mldsa-native does not currently implement HashML-DSA, the hash-based variant of ML-DSA defined in FIPS 204. The current implementation focuses on the standard ML-DSA signature scheme.
+Yes. mldsa-native supports HashML-DSA, the pre-hashing variant of ML-DSA defined in FIPS 204 Algorithms 4 and 5.
+
+mldsa-native provides two levels of API:
+- `crypto_sign_signature_pre_hash_internal` and `crypto_sign_verify_pre_hash_internal` - Low-level functions that accept a pre-hashed message digest. This function supports all 12 allowed hash functions.
+- `crypto_sign_signature_pre_hash_shake256` and `crypto_sign_verify_pre_hash_shake256` - High-level functions that perform SHAKE256 pre-hashing internally for convenience. Currently, only SHAKE256 is supported. If you require another hash function, use the `*_pre_hash_internal` functions or open an issue.
 
 ### Will I be able to bring my own backend?