Crate cose_minicbor 

No std CBOR Object Signing and Encryption, Cose RFC 9052 / RFC 9053.

This crate provides lightweight, no_std-friendly methods and structure for decoding COSE message types (e.g. CoseSign, CoseSign1, CoseMac, CoseMac0) using minicbor.

It is inspired by cose-rust but targeted at constrained / embedded environments: the emphasis is on borrowed decoding, minimal allocations and lazy parsing.

The implementation targets the COSE/CBOR stack specified by:

• RFC 9052 — COSE
• RFC 9053 — CBOR Object Signing and Encryption (COSE)

And supports the cryptographic profiles depicted in:

• Cryptographic Algorithms for IoT (SUIT MTI draft)

Scope & goals

• Decode-first: focus on decoding COSE structures and exposing ergonomic Rust types to inspect and verify messages.
• no_std-friendly: designed to build on targets without std or alloc.

Cryptographic backends

Cryptographic verification is delegated to backend crates (enable via Cargo features). Typical backends (links to crates):

• signature verification:
  • p256 — P-256 / ECDSA support.
  • ed25519-dalek — Ed25519 signatures.
  • hss_lms — LMS (Leighton-Micali Signatures.
• MAC / digest:
  • hmac — HMAC interface.
  • sha2 — SHA-2 family (SHA-256, SHA-384).

Modularity and Feature Profiles

This crate is designed to be highly modular: each cryptographic backend and algorithm is behind its own feature flag. This allows users to compile only the code they need, minimizing binary size — which is particularly important for no_std and embedded targets.

SUIT MTI Profiles

This crate provides predefined cryptographic profiles following the SUIT MTI draft for IoT device update verification.

Each MTI profile is a bundle of features corresponding to the cryptographic algorithms and workflows recommended by SUIT:

Profile	Description	Features Enabled
suit-sha256-hmac	HMAC/SHA-256 only	sha256, hmac256, decrypt
suit-sha256-hmac-a128kw	HMAC/SHA-256 + AES-128 Key Wrap	sha256, hmac256, a128kw
suit-sha256-hmac-a256kw	HMAC/SHA-256 + AES-256 Key Wrap	sha256, hmac256, a256kw
suit-sha256-hmac-ecdh_es-a256kw	HMAC/SHA-256 + ECDH-ES + AES-256 Key Wrap	sha256, hmac256, ecdh_es, a256kw
suit-sha256-es256	SHA-256 + ES256 signatures	sha256, es256
suit-sha256-ed25519	SHA-256 + Ed25519 signatures	sha256, ed25519
suit-sha256-hsslms	SHA-256 + HSS/LMS signatures	sha256, hss_lms

Note: Using these profiles ensures all required features for a given cryptographic workflow are enabled automatically. This avoids subtle bugs where functions such as decrypt_process or HMAC verification are unavailable due to missing features.

---

Example: HMAC Verification with AES-128 KW

This example demonstrates how to verify a CoseMac using an A128 Key Wrap KEK following the SUIT HMAC profile.

use cose_minicbor::cose::CoseMac;
use cose_minicbor::cose_keys::{CoseAlg, CoseKey, CoseKeySetBuilder, KeyOp, KeyType};
use hex_literal::hex;
use minicbor::Decode;

// 1. Build a COSE Key Set containing a KEK for AES-128 KW
let mut builder: CoseKeySetBuilder<200> = CoseKeySetBuilder::try_new().unwrap();

let mut key = CoseKey::new(KeyType::Symmetric);
key.alg(CoseAlg::A128KW);
key.k(&hex!("c1e60d0db5c6cbdac37e8473b412f6b0")).unwrap();
key.kid(b"our-secret");
key.key_op(KeyOp::UnwrapKey);

builder.push_key(key).unwrap();
let key_set_bytes = builder.into_bytes().unwrap();

// 2. Decode a COSE Mac from CBOR (example)
let mac_bytes = cbor_diag::parse_diag("
[
    /protected/ h'A10105',
    /unprotected/{},
    /payload/ h'546869732069732074686520636F6E74656E742E',
    /tag/ h'2bdcc89f058216b8a208ddc6d8b54aa91f48bd63484986565105c9ad5a6682f6',
    /recipients/ [
        [
            /protected/ h'',
            /unprotected/ {
                /alg/ 1: -3,
                /kid/ 4: h'6F75722D736563726574'
            },
            /ciphertext/ h'45f19543a4ea912e07fa280d14f7397da96f446a0246d983cd3457e038aec3e21fc286f139d1edd2'
        ]
    ]

]")
    .unwrap()
    .to_bytes();

let mac: CoseMac = minicbor::decode(&mac_bytes).expect("Invalid CoseMac format");

// 3. Verify the MAC using the COSE Key Set
mac.suit_verify_mac(None, &key_set_bytes)
    .expect("HMAC verification failed");

License

SPDX: MIT

Re-exports

pub use errors::CoseError;

Modules

cose

cose_keys

errors