This project is a Python implementation of the IETF CBOR Encoded Message Syntax (COSE). COSE has reached RFC status and is now available at RFC 8152.

$ pip install cose

⚠️WARNING⚠️: There is package on PyPI called pycose which contains old code from this repository. Since I am not the maintainer I cannot update that package or remove it.

CBOR Encoded Message Syntax (COSE) is a data format for concise representation of small messages RFC 8152. COSE is optimized for low power devices. The messages can be encrypted, MAC'ed and signed. There are 6 different types of COSE messages:

• Encrypt0: An encrypted COSE message with a single recipient. The payload and AAD are protected by a shared CEK (Content Encryption Keys)
• Encrypt: An encrypted COSE message can have multiple recipients. For each recipient the CEK is encrypted with a KEK (Key Encryption Key) - using AES key wrap - and added to the message.
• MAC0: An authenticated COSE message with one recipient.
• MAC: An authenticated COSE message that can have multiple recipients. For each recipient, the authentication key is encrypted with a KEK and added to the message.
• Sign0: A signed COSE message with a single signature.
• Sign: A COSE message that has been signed by multiple entities (each signature is carried in a COSE signature structure, added to the message).

A basic COSE message consists of 2 information buckets and the payload:

• Protected header: This message field contains information that needs to be protected. This information is taken into account during the encryption, calculation of the MAC or the signature.
• Unprotected header: The information contained in the unprotected header is not protected by the cryptographic algorithms.
• Payload: Contains the payload of the message, protected (mac'ed, signed or encrypted) by the cryptographic algorithms.

Additionally, based on the message type, other message fields can be added:

• MAC or signature (for MAC0 or Sign1 messages)
• COSE recipients or COSE signatures (for MAC, Encrypt, and Sign messages)

The project depends on pyca/cryptography for all cryptographic operations, except the deterministic ECDSA algorithm. For deterministic ECDSA cose uses python-ecdsa.

More documentation on COSE and the cose API can be found at: https://pycose.readthedocs.io