Enum SignatureAlgorithm 

#[repr(u8)]
pub enum SignatureAlgorithm {
    Ed25519 = 1,
    HybridMlDsa44Ed25519 = 2,
    HybridMlDsa65Ed25519 = 3,
}

Wire-stable numeric tag for the signature algorithm used in a DelegationCert.

Every cert carries exactly one of these tags, written as a single byte in DelegationCert::version ≥ 2 certs. Verifiers that encounter an unknown tag MUST reject the cert with A1Error::UnsupportedAlgorithm. The numeric representation is frozen for the lifetime of the protocol.

Forward compatibility

New variants are additive. A verifier compiled against an older version of this library simply cannot validate the new variant and rejects it — it does not silently fall back to a weaker scheme.

Quantum migration path

1. Today: issue all certs with Ed25519 (default). No changes required.
2. Transition: issue root passports with HybridMlDsa44Ed25519. Classical sub-delegations remain valid — see ChainAlgorithmCompatibility.
3. Post-migration: all certs use a hybrid or pure-PQ algorithm.

The post-quantum feature flag wires in the real ML-DSA signer backend; until then the framework validates the Ed25519 component and the binding context in HybridSignature::pq_context, ensuring the wire format is identical and no migration is required when PQ support is activated.

Variants

Ed25519 = 1

Pure Ed25519 — the default for all v2.8.0 deployments.

HybridMlDsa44Ed25519 = 2

CRYSTALS-Dilithium 2 (ML-DSA-44) + Ed25519 hybrid.

Both components are required for verification. A verifier that cannot evaluate the ML-DSA component MUST reject with UnsupportedAlgorithm. Security category: 128-bit post-quantum, NIST ML-DSA-44.

HybridMlDsa65Ed25519 = 3

CRYSTALS-Dilithium 3 (ML-DSA-65) + Ed25519 hybrid.

Higher-assurance variant. Security category: 192-bit post-quantum, NIST ML-DSA-65. Recommended for financial and government deployments.

Implementations

impl SignatureAlgorithm

pub fn as_u8(self) -> u8

pub fn from_u8(v: u8) -> Result<Self, A1Error>

pub fn requires_pq(self) -> bool

Whether this algorithm requires a post-quantum signing component.

pub fn pq_public_key_len(self) -> usize

Expected byte length of the PQ public key for this algorithm.

ML-DSA-44: 1312 bytes. ML-DSA-65: 1952 bytes. Ed25519: 0.

pub fn pq_signature_len(self) -> usize

Expected byte length of the PQ signature for this algorithm.

ML-DSA-44: 2420 bytes. ML-DSA-65: 3309 bytes. Ed25519: 0.

pub fn name(self) -> &'static str

Canonical string name for logging and diagnostics.

Trait Implementations

impl Clone for SignatureAlgorithm

fn clone(&self) -> SignatureAlgorithm

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for SignatureAlgorithm

impl Debug for SignatureAlgorithm

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for SignatureAlgorithm

fn default() -> SignatureAlgorithm

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for SignatureAlgorithm

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Display for SignatureAlgorithm

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for SignatureAlgorithm

impl Hash for SignatureAlgorithm

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for SignatureAlgorithm

fn eq(&self, other: &SignatureAlgorithm) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for SignatureAlgorithm

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for SignatureAlgorithm