Enum CoseAlg 

#[non_exhaustive]
pub enum CoseAlg {
    Ed25519,
    Esp256,
    Hmac256_64,
    Hmac256_256,
}

A COSE algorithm this crate signs or verifies with.

Deviation from the ADR 0006 §1 sketch, which types alg as coset::iana::Algorithm: that is an open registry of about a hundred values, so every verifier would need its own allowlist and every resolver would be asked about algorithms it can never honour. Here the allowlist is the type. CoseAlg::from_id is the only way a wire value becomes an algorithm, and it knows four ids. The deprecated polymorphic ids -8 (EdDSA) and -7 (ES256), which RFC 9864 replaces with the fully specified -19 and -9, are rejected like any other unknown id: nothing has shipped with them, so there is nothing to stay compatible with.

#[non_exhaustive] because Q5 reserves a hybrid post-quantum alg value: adding it is a new variant, not a wire break.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Ed25519

-19, Ed25519 (RFC 9864). The default for COSE_Sign1 (Q2).

Esp256

-9, ESP256: ECDSA over P-256 with SHA-256 (RFC 9864). Opt-in, for keys held in a KMS, an HSM or as non-extractable WebCrypto keys (Q2).

Hmac256_64

4, HMAC 256/64: HMAC-SHA-256 truncated to its first 8 bytes. Safe only because a forgery needs online attempts, which are rate limited (§3).

Hmac256_256

5, HMAC 256/256.

Implementations

impl CoseAlg

pub const ALL: &'static [CoseAlg]

Every accepted algorithm, for tests and for exhaustive tables. A slice, not an array, so that Q5’s reserved hybrid algorithm can be added without changing this constant’s type.

pub const fn id(self) -> i64

The IANA “COSE Algorithms” value written into protected label 1.

pub const fn from_id(id: i64) -> Option<CoseAlg>

The algorithm for a wire value, or None for anything outside the allowlist, including -8 and -7.

pub const fn mode(self) -> CoseMode

The message structure this algorithm belongs to. A tag-17 message carrying a signature algorithm, or a tag-18 message carrying a MAC algorithm, is rejected before any key is looked up.

pub const fn signature_len(self) -> usize

The exact length of the signature or tag, in bytes. Q5: nothing in this crate assumes 64; every size is read from here. Both signature algorithms happen to be 64 (Ed25519, and ESP256’s fixed-size r‖s).

Trait Implementations

impl Clone for CoseAlg

fn clone(&self) -> CoseAlg

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for CoseAlg

impl Debug for CoseAlg

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

Formats the value using the given formatter.

impl Eq for CoseAlg

impl Hash for CoseAlg

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

where __H: Hasher,

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 CoseAlg

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for CoseAlg