Module crypto 

COSE key parsing and signature verification (ES256 / RS256) via ring, plus base64url helpers and CSPRNG challenge generation.

Security

• All cryptographic primitives come from ring (constant-time ECDSA/RSA verification). This crate contains no hand-rolled cryptography; the only custom encoding is RFC 5280 DER wrapping of already-validated RSA modulus/exponent byte strings, which never touches secret material.
• Signature verification is constant-result: on failure the payload and signature are discarded and only an error variant is returned.

Enums

CosePublicKey

Parsed COSE public key (EC2 or RSA).

Constants

COSE_ALG_ES256

COSE algorithm: ECDSA w/ SHA-256 on P-256.

COSE_ALG_RS256

COSE algorithm: RSASSA-PKCS1-v1_5 w/ SHA-256.

COSE_KTY_EC2

COSE key type: Elliptic-Curve key pair with x/y coordinates.

COSE_KTY_OKP

COSE key type: Octet Key Pair (Ed25519 et al.). Not supported.

COSE_KTY_RSA

COSE key type: RSA key.

Functions

alg_to_name

Convert a COSE algorithm ID to a human-readable name.

base64_decode_urlsafe

Base64url decode (RFC 4648 §5, no padding required; standard alphabet with padding is also accepted by the engine’s forgiving handling).

base64_encode_urlsafe

Base64url encode (RFC 4648 §5, no padding), as required by the WebAuthn JSON serialization conventions.

cbor_bytes

Extract a CBOR byte string from a value.

cbor_map_entries

Parse a CBOR map into ordered (i64, Value) entries.

generate_challenge_bytes

Generate 32 random bytes (256 bits of entropy) for a WebAuthn challenge.

parse_cose_key

Parse a COSE key from its CBOR encoding (RFC 9052).

verify_cose_signature

Verify a COSE signature using the parsed public key.