cwt 1.1.0

A Python implementation of CBOR Web Token (CWT) and CBOR Object Signing and Encryption (COSE).

Python CWT

Python CWT is a CBOR Web Token (CWT) and CBOR Object Signing and Encryption (COSE) implementation compliant with:

• RFC8392: CWT (CBOR Web Token)
• RFC8152: COSE (CBOR Object Signing and Encryption)
• and related various specifications. See Referenced Specifications.

It is designed to make users who already know about JWS/JWE/JWT be able to use it in ease. Little knowledge of CBOR/COSE/CWT is required to use it.

You can install Python CWT with pip:

$ pip install cwt

And then, you can use it as follows:

>>> import cwt
>>> from cwt import COSEKey
>>> key = COSEKey.from_symmetric_key(alg="HS256", kid="01")
>>> token = cwt.encode({"iss": "coaps://as.example", "sub": "dajiaji", "cti": "123"}, key)
>>> token.hex()
'd18443a10105a05835a60172636f6170733a2f2f61732e6578616d706c65026764616a69616a690743313233041a60c6a60b051a60c697fb061a60c697fb582019d4a89e141e3a8805ba1c90d81a8a2dd8261464dce379d8af8044d1cc062258'
>>> cwt.decode(token, key)
{1: 'coaps://as.example', 2: 'dajiaji', 7: b'123', 4: 1620088759, 5: 1620085159, 6: 1620085159}

See Document for details.

Index

• Installing
• CWT Usage Examples
  • MACed CWT
  • Signed CWT
  • Encrypted CWT
  • Nested CWT
  • CWT with User Settings (e.g., expires_in)
  • CWT with User-Defined Claims
  • CWT with PoP Key
• COSE Usage Examples
  • COSE MAC0
  • COSE MAC
    • Direct Key Distribution
    • Direct Key with KDF
    • AES Key Wrap
    • Direct key Agreement
    • Key Agreement with Key Wrap
  • COSE Encrypt0
  • COSE Encrypt
    • Direct Key Distribution
    • Direct Key with KDF
    • AES Key Wrap
    • Direct key Agreement
    • Key Agreement with Key Wrap
  • COSE Signature1
  • COSE Signature
• API Reference
• Supported CWT Claims
• Supported COSE Algorithms
• Referenced Specifications
• Tests

Installing

Install with pip:

pip install cwt

CWT Usage Examples

Followings are typical and basic examples which create various types of CWTs, verify and decode them.

CWT API in the examples are built on top of COSE API.

See API Reference and CWT Usage Examples on document for more details.

MACed CWT

Create a MACed CWT with HS256, verify and decode it as follows:

import cwt
from cwt import Claims, COSEKey

try:
    key = COSEKey.from_symmetric_key(alg="HS256", kid="01")
    token = cwt.encode({"iss": "coaps://as.example", "sub": "dajiaji", "cti": "123"}, key)
    decoded = cwt.decode(token, key)

    # If you want to treat the result like a JWT;
    readable = Claims.new(decoded)
    assert readable.iss == 'coaps://as.example'
    assert readable.sub == 'dajiaji'
    assert readable.cti == '123'
    # readable.exp == 1620088759
    # readable.nbf == 1620085159
    # readable.iat == 1620085159

except Exception as err:
    # All the other examples in this document omit error handling but this CWT library
    # can throw following errors:
    #   ValueError: Invalid arguments.
    #   EncodeError: Failed to encode.
    #   VerifyError: Failed to verify.
    #   DecodeError: Failed to decode.
    print(err)

A raw CWT structure (Dict[int, Any]) can also be used as follows:

import cwt
from cwt import COSEKey

key = COSEKey.from_symmetric_key(alg="HS256", kid="01")
token = cwt.encode({1: "coaps://as.example", 2: "dajiaji", 7: b"123"}, key)

decoded = cwt.decode(token, key)

MAC algorithms other than HS256 are listed in Supported COSE Algorithms.

Signed CWT

Create an Ed25519 key pair:

$ openssl genpkey -algorithm ed25519 -out private_key.pem
$ openssl pkey -in private_key.pem -pubout -out public_key.pem

Create a Signed CWT with Ed25519, verify and decode it with the key pair as follows:

import cwt
from cwt import COSEKey

with open("./private_key.pem") as key_file:
    private_key = COSEKey.from_pem(key_file.read(), kid="01")
with open("./public_key.pem") as key_file:
    public_key = COSEKey.from_pem(key_file.read(), kid="01")


token = cwt.encode(
    {"iss": "coaps://as.example", "sub": "dajiaji", "cti": "123"}, private_key
)

decoded = cwt.decode(token, public_key)

JWKs can also be used instead of the PEM-formatted keys as follows:

import cwt
from cwt import COSEKey

private_key = COSEKey.from_jwk({
    "kty": "OKP",
    "d": "L8JS08VsFZoZxGa9JvzYmCWOwg7zaKcei3KZmYsj7dc",
    "use": "sig",
    "crv": "Ed25519",
    "kid": "01",
    "x": "2E6dX83gqD_D0eAmqnaHe1TC1xuld6iAKXfw2OVATr0",
    "alg": "EdDSA",
})
public_key = COSEKey.from_jwk({
    "kty": "OKP",
    "use": "sig",
    "crv": "Ed25519",
    "kid": "01",
    "x": "2E6dX83gqD_D0eAmqnaHe1TC1xuld6iAKXfw2OVATr0",
})

token = cwt.encode(
    {"iss": "coaps://as.example", "sub": "dajiaji", "cti": "123"}, private_key
)

decoded = cwt.decode(token, public_key)

Signing algorithms other than Ed25519 are listed in Supported COSE Algorithms.

Encrypted CWT

Create an encrypted CWT with ChaCha20/Poly1305 and decrypt it as follows:

import cwt
from cwt import COSEKey

enc_key = COSEKey.from_symmetric_key(alg="ChaCha20/Poly1305", kid="01")
token = cwt.encode({"iss": "coaps://as.example", "sub": "dajiaji", "cti": "123"}, enc_key)

decoded = cwt.decode(token, enc_key)

Encryption algorithms other than ChaCha20/Poly1305 are listed in Supported COSE Algorithms.

Nested CWT

Create a signed CWT and encrypt it, and then decrypt and verify the nested CWT as follows.

import cwt
from cwt import COSEKey

with open("./private_key.pem") as key_file:
    private_key = COSEKey.from_pem(key_file.read(), kid="sig-01")
with open("./public_key.pem") as key_file:
    public_key = COSEKey.from_pem(key_file.read(), kid="sig-01")

# Creates a CWT with ES256 signing.
token = cwt.encode(
    {"iss": "coaps://as.example", "sub": "dajiaji", "cti": "123"}, private_key
)

# Encrypts the signed CWT.
enc_key = COSEKey.from_symmetric_key(alg="ChaCha20/Poly1305", kid="enc-01")
nested = cwt.encode(token, enc_key)

# Decrypts and verifies the nested CWT.
decoded = cwt.decode(nested, [enc_key, public_key])

CWT with User Settings

The cwt in cwt.encode() and cwt.decode() above is a global CWT class instance created with default settings in advance. The default settings are as follows:

• expires_in: 3600 seconds. This is the default lifetime in seconds of CWTs.
• leeway: 60 seconds. This is the default leeway in seconds for validating exp and nbf.

If you want to change the settings, you can create your own CWT class instance as follows:

from cwt import COSEKey, CWT

key = COSEKey.from_symmetric_key(alg="HS256", kid="01")
mycwt = CWT.new(expires_in=3600*24, leeway=10)
token = mycwt.encode({"iss": "coaps://as.example", "sub": "dajiaji", "cti": "123"}, key)
decoded = mycwt.decode(token, key)

CWT with User-Defined Claims

You can use your own claims as follows:

Note that such user-defined claim's key should be less than -65536.

import cwt
from cwt import COSEKey

with open("./private_key.pem") as key_file:
    private_key = COSEKey.from_pem(key_file.read(), kid="01")
with open("./public_key.pem") as key_file:
    public_key = COSEKey.from_pem(key_file.read(), kid="01")
token = cwt.encode(
    {
        1: "coaps://as.example",  # iss
        2: "dajiaji",  # sub
        7: b"123",  # cti
        -70001: "foo",
        -70002: ["bar"],
        -70003: {"baz": "qux"},
        -70004: 123,
    },
    private_key,
)
raw = cwt.decode(token, public_key)
assert raw[-70001] == "foo"
assert raw[-70002][0] == "bar"
assert raw[-70003]["baz"] == "qux"
assert raw[-70004] == 123

readable = Claims.new(raw)
assert readable.get(-70001) == "foo"
assert readable.get(-70002)[0] == "bar"
assert readable.get(-70003)["baz"] == "qux"
assert readable.get(-70004) == 123

User-defined claims can also be used with JSON-based claims as follows:

import cwt
from cwt import Claims, COSEKey

with open("./private_key.pem") as key_file:
    private_key = COSEKey.from_pem(key_file.read(), kid="01")
with open("./public_key.pem") as key_file:
    public_key = COSEKey.from_pem(key_file.read(), kid="01")

my_claim_names = {
    "ext_1": -70001,
    "ext_2": -70002,
    "ext_3": -70003,
    "ext_4": -70004,
}

cwt.set_private_claim_names(my_claim_names)
token = cwt.encode(
    {
        "iss": "coaps://as.example",
        "sub": "dajiaji",
        "cti": b"123",
        "ext_1": "foo",
        "ext_2": ["bar"],
        "ext_3": {"baz": "qux"},
        "ext_4": 123,
    },
    private_key,
)
raw = cwt.decode(token, public_key)
readable = Claims.new(
    raw,
    private_claims_names=my_claim_names,
)
assert readable.get("ext_1") == "foo"
assert readable.get("ext_2")[0] == "bar"
assert readable.get("ext_3")["baz"] == "qux"
assert readable.get("ext_4") == 123

CWT with PoP Key

Python CWT supports Proof-of-Possession Key Semantics for CBOR Web Tokens (CWTs). A CWT can include a PoP key as follows:

On the issuer side:

import cwt
from cwt import COSEKey

# Prepares a signing key for CWT in advance.
with open("./private_key_of_issuer.pem") as key_file:
    private_key = COSEKey.from_pem(key_file.read(), kid="issuer-01")

# Sets the PoP key to a CWT for the presenter.
token = cwt.encode(
    {
        "iss": "coaps://as.example",
        "sub": "dajiaji",
        "cti": "123",
        "cnf": {
            "jwk": {  # Provided by the CWT presenter.
                "kty": "OKP",
                "use": "sig",
                "crv": "Ed25519",
                "kid": "presenter-01",
                "x": "2E6dX83gqD_D0eAmqnaHe1TC1xuld6iAKXfw2OVATr0",
                "alg": "EdDSA",
            },
        },
    },
    private_key,
)

# Issues the token to the presenter.

On the CWT presenter side:

import cwt
from cwt import COSEKey

# Prepares a private PoP key in advance.
with open("./private_pop_key.pem") as key_file:
    pop_key_private = COSEKey.from_pem(key_file.read(), kid="presenter-01")

# Receives a message (e.g., nonce)  from the recipient.
msg = b"could-you-sign-this-message?"  # Provided by recipient.

# Signs the message with the private PoP key.
sig = pop_key_private.sign(msg)

# Sends the msg and the sig with the CWT to the recipient.

On the CWT recipient side:

import cwt
from cwt import Claims, COSEKey

# Prepares the public key of the issuer in advance.
with open("./public_key_of_issuer.pem") as key_file:
    public_key = COSEKey.from_pem(key_file.read(), kid="issuer-01")

# Verifies and decodes the CWT received from the presenter.
raw = cwt.decode(token, public_key)
decoded = Claims.new(raw)

# Extracts the PoP key from the CWT.
extracted_pop_key = COSEKey.new(decoded.cnf)  # = raw[8][1]

# Then, verifies the message sent by the presenter
# with the signature which is also sent by the presenter as follows:
extracted_pop_key.verify(msg, sig)

Usage Examples shows other examples which use other confirmation methods for PoP keys.

COSE Usage Examples

Followings are typical and basic examples which create various types of COSE messages, verify and decode them.

See API Reference and COSE Usage Examples on document for more details.

COSE MAC0

Create a COSE MAC0 message, verify and decode it as follows:

from cwt import COSE, COSEKey

mac_key = COSEKey.from_symmetric_key(alg="HS256", kid="01")
ctx = COSE.new(alg_auto_inclusion=True, kid_auto_inclusion=True)
encoded = ctx.encode_and_mac(b"Hello world!", mac_key)
assert b"Hello world!" == ctx.decode(encoded, mac_key)

Following two samples are other ways of writing the above example:

from cwt import COSE, COSEKey

mac_key = COSEKey.from_symmetric_key(alg="HS256", kid="01")
ctx = COSE.new()
encoded = ctx.encode_and_mac(
    b"Hello world!",
    mac_key,
    protected={"alg": "HS256"},
    unprotected={"kid": "01"},
)
assert b"Hello world!" == ctx.decode(encoded, mac_key)

from cwt import COSE, COSEKey

mac_key = COSEKey.from_symmetric_key(alg="HS256", kid="01")
ctx = COSE.new()
encoded = ctx.encode_and_mac(
    b"Hello world!",
    mac_key,
    protected={1: 5},
    unprotected={4: b"01"},
)
assert b"Hello world!" == ctx.decode(encoded, mac_key)

COSE MAC

Direct Key Distribution for MAC

The direct key distribution shares a MAC key between the sender and the recipient that is used directly. The follwing example shows the simplest way to make a COSE MAC message, verify and decode it with the direct key distribution method.

from cwt import COSE, COSEKey, Recipient

# The sender makes a COSE MAC message as follows:
mac_key = COSEKey.from_symmetric_key(alg="HS512", kid="01")
r = Recipient.from_jwk({"alg": "direct"})
r.apply(mac_key)
ctx = COSE.new()
encoded = ctx.encode_and_mac(b"Hello world!", mac_key, recipients=[r])

# The recipient has the same MAC key and can verify and decode it:
assert b"Hello world!" == ctx.decode(encoded, mac_key)

Direct Key with KDF for MAC

from secrets import token_bytes
from cwt import COSE, COSEKey, Recipient

shared_material = token_bytes(32)
shared_key = COSEKey.from_symmetric_key(shared_material, kid="01")

# The sender side:
r = Recipient.from_jwk(
    {
        "kty": "oct",
        "alg": "direct+HKDF-SHA-256",
    },
)
mac_key = r.apply(shared_key, context={"alg": "HS256"})
ctx = COSE.new(alg_auto_inclusion=True)
encoded = ctx.encode_and_mac(
    b"Hello world!",
    key=mac_key,
    recipients=[r],
)

# The recipient side:
assert b"Hello world!" == ctx.decode(encoded, shared_key, context={"alg": "HS256"})

AES Key Wrap for MAC

The AES key wrap algorithm can be used to wrap a MAC key as follows:

from cwt import COSE, COSEKey, Recipient

# The sender side:
mac_key = COSEKey.from_symmetric_key(alg="HS512")
r = Recipient.from_jwk(
    {
        "alg": "A128KW",
        "kid": "01",
        "k": "hJtXIZ2uSN5kbQfbtTNWbg",  # A shared wrapping key
    },
)
r.apply(mac_key)
ctx = COSE.new(alg_auto_inclusion=True)
encoded = ctx.encode_and_mac(b"Hello world!", key=mac_key, recipients=[r])

# The recipient side:
shared_key = COSEKey.from_jwk(
    {
        "kty": "oct",
        "alg": "A128KW",
        "kid": "01",
        "k": "hJtXIZ2uSN5kbQfbtTNWbg",
    },
)
assert b"Hello world!" == ctx.decode(encoded, shared_key)

Direct Key Agreement for MAC

The direct key agreement methods can be used to create a shared secret. A KDF (Key Distribution Function) is then applied to the shared secret to derive a key to be used to protect the data. The follwing example shows a simple way to make a COSE Encrypt message, verify and decode it with the direct key agreement methods (ECDH-ES+HKDF-256 with various curves).

from cwt import COSE, COSEKey, Recipient

# The sender side:
r = Recipient.from_jwk(
    {
        "kty": "EC",
        "alg": "ECDH-ES+HKDF-256",
        "crv": "P-256",
    },
)
# The following key is provided by the recipient in advance.
pub_key = COSEKey.from_jwk(
    {
        "kty": "EC",
        "alg": "ECDH-ES+HKDF-256",
        "kid": "01",
        "crv": "P-256",
        "x": "Ze2loSV3wrroKUN_4zhwGhCqo3Xhu1td4QjeQ5wIVR0",
        "y": "HlLtdXARY_f55A3fnzQbPcm6hgr34Mp8p-nuzQCE0Zw",
    }
)
mac_key = r.apply(recipient_key=pub_key, context={"alg": "HS256"})
ctx = COSE.new(alg_auto_inclusion=True)
encoded = ctx.encode_and_mac(
    b"Hello world!",
    key=mac_key,
    recipients=[r],
)

# The recipient side:
# The following key is the private key of the above pub_key.
priv_key = COSEKey.from_jwk(
    {
        "kty": "EC",
        "alg": "ECDH-ES+HKDF-256",
        "kid": "01",
        "crv": "P-256",
        "x": "Ze2loSV3wrroKUN_4zhwGhCqo3Xhu1td4QjeQ5wIVR0",
        "y": "HlLtdXARY_f55A3fnzQbPcm6hgr34Mp8p-nuzQCE0Zw",
        "d": "r_kHyZ-a06rmxM3yESK84r1otSg-aQcVStkRhA-iCM8",
    }
)
# The enc_key will be derived in decode() with priv_key and
# the sender's public key which is conveyed as the recipient
# information structure in the COSE Encrypt message (encoded).
assert b"Hello world!" == ctx.decode(encoded, priv_key, context={"alg": "HS256"})

Key Agreement with Key Wrap for MAC

from cwt import COSE, COSEKey, Recipient

# The sender side:
mac_key = COSEKey.from_symmetric_key(alg="HS256")
r = Recipient.from_jwk(
    {
        "kty": "EC",
        "crv": "P-256",
        "alg": "ECDH-SS+A128KW",
        "x": "7cvYCcdU22WCwW1tZXR8iuzJLWGcd46xfxO1XJs-SPU",
        "y": "DzhJXgz9RI6TseNmwEfLoNVns8UmvONsPzQDop2dKoo",
        "d": "Uqr4fay_qYQykwcNCB2efj_NFaQRRQ-6fHZm763jt5w",
    }
)
pub_key = COSEKey.from_jwk(
    {
        "kty": "EC",
        "crv": "P-256",
        "kid": "[e-mail]",
        "x": "Ze2loSV3wrroKUN_4zhwGhCqo3Xhu1td4QjeQ5wIVR0",
        "y": "HlLtdXARY_f55A3fnzQbPcm6hgr34Mp8p-nuzQCE0Zw",
    }
)
r.apply(mac_key, recipient_key=pub_key, context={"alg": "HS256"})
ctx = COSE.new(alg_auto_inclusion=True)
encoded = ctx.encode_and_mac(
    b"Hello world!",
    key=mac_key,
    recipients=[r],
)

# The recipient side:
priv_key = COSEKey.from_jwk(
    {
        "kty": "EC",
        "crv": "P-256",
        "alg": "ECDH-SS+A128KW",
        "kid": "[e-mail]",
        "x": "Ze2loSV3wrroKUN_4zhwGhCqo3Xhu1td4QjeQ5wIVR0",
        "y": "HlLtdXARY_f55A3fnzQbPcm6hgr34Mp8p-nuzQCE0Zw",
        "d": "r_kHyZ-a06rmxM3yESK84r1otSg-aQcVStkRhA-iCM8",
    }
)
assert b"Hello world!" == ctx.decode(encoded, priv_key, context={"alg": "HS256"})

COSE Encrypt0

Create a COSE Encrypt0 message, verify and decode it as follows:

from cwt import COSE, COSEKey

enc_key = COSEKey.from_symmetric_key(alg="ChaCha20/Poly1305", kid="01")
ctx = COSE.new(alg_auto_inclusion=True, kid_auto_inclusion=True)
encoded = ctx.encode_and_encrypt(b"Hello world!", enc_key)
decoded = ctx.decode(encoded, enc_key)

COSE Encrypt

Direct Key Distribution for encryption

The direct key distribution shares a MAC key between the sender and the recipient that is used directly. The follwing example shows the simplest way to make a COSE MAC message, verify and decode it with the direct key distribution method.

from cwt import COSE, COSEKey, Recipient

enc_key = COSEKey.from_symmetric_key(alg="ChaCha20/Poly1305", kid="01")

# The sender side:
nonce = enc_key.generate_nonce()
r = Recipient.from_jwk({"alg": "direct"})
r.apply(enc_key)
ctx = COSE.new()
encoded = ctx.encode_and_encrypt(
    b"Hello world!",
    enc_key,
    nonce=nonce,
    recipients=[r],
)

# The recipient side:
assert b"Hello world!" == ctx.decode(encoded, enc_key)

Direct Key with KDF for encryption

from cwt import COSE, COSEKey, Recipient

shared_material = token_bytes(32)
shared_key = COSEKey.from_symmetric_key(shared_material, kid="01")

# The sender side:
r = Recipient.from_jwk(
    {
        "kty": "oct",
        "alg": "direct+HKDF-SHA-256",
    },
)
enc_key = r.apply(shared_key, context={"alg": "A256GCM"})
ctx = COSE.new(alg_auto_inclusion=True)
encoded = ctx.encode_and_encrypt(
    b"Hello world!",
    key=enc_key,
    recipients=[r],
)
# The recipient side:
assert b"Hello world!" == ctx.decode(encoded, shared_key, context={"alg": "A256GCM"})

AES Key Wrap for encryption

The AES key wrap algorithm can be used to wrap a MAC key as follows:

from cwt import COSE, COSEKey, Recipient

# The sender side:
r = Recipient.from_jwk(
    {
        "kty": "oct",
        "alg": "A128KW",
        "kid": "01",
        "k": "hJtXIZ2uSN5kbQfbtTNWbg",  # A shared wrapping key
    },
)
enc_key = COSEKey.from_symmetric_key(alg="ChaCha20/Poly1305")
r.apply(enc_key)
ctx = COSE.new(alg_auto_inclusion=True)
encoded = ctx.encode_and_encrypt(b"Hello world!", key=enc_key, recipients=[r])

# The recipient side:
shared_key = COSEKey.from_jwk(
    {
        "kty": "oct",
        "alg": "A128KW",
        "kid": "01",
        "k": "hJtXIZ2uSN5kbQfbtTNWbg",
    },
)
assert b"Hello world!" == ctx.decode(encoded, shared_key)

Direct Key Agreement for encryption

The direct key agreement methods can be used to create a shared secret. A KDF (Key Distribution Function) is then applied to the shared secret to derive a key to be used to protect the data. The follwing example shows a simple way to make a COSE Encrypt message, verify and decode it with the direct key agreement methods (ECDH-ES+HKDF-256 with various curves).

from cwt import COSE, COSEKey, Recipient

# The sender side:
r = Recipient.from_jwk(
    {
        "kty": "OKP",
        "alg": "ECDH-ES+HKDF-256",
        "crv": "X25519",
    },
)
pub_key = COSEKey.from_jwk(
    {
        "kty": "OKP",
        "alg": "ECDH-ES+HKDF-256",
        "kid": "01",
        "crv": "X25519",
        "x": "y3wJq3uXPHeoCO4FubvTc7VcBuqpvUrSvU6ZMbHDTCI",
    }
)
enc_key = r.apply(recipient_key=pub_key, context={"alg": "A128GCM"})
ctx = COSE.new(alg_auto_inclusion=True)
encoded = ctx.encode_and_encrypt(
    b"Hello world!",
    key=enc_key,
    recipients=[r],
)

# The recipient side:
priv_key = COSEKey.from_jwk(
    {
        "kty": "OKP",
        "alg": "ECDH-ES+HKDF-256",
        "kid": "01",
        "crv": "X25519",
        "x": "y3wJq3uXPHeoCO4FubvTc7VcBuqpvUrSvU6ZMbHDTCI",
        "d": "vsJ1oX5NNi0IGdwGldiac75r-Utmq3Jq4LGv48Q_Qc4",
    }
)
assert b"Hello world!" == ctx.decode(encoded, priv_key, context={"alg": "A128GCM"})

Key Agreement with Key Wrap for encryption

from cwt import COSE, COSEKey, Recipient

# The sender side:
enc_key = COSEKey.from_symmetric_key(alg="A128GCM")
nonce = enc_key.generate_nonce()
r = Recipient.from_jwk(
    {
        "kty": "EC",
        "crv": "P-256",
        "alg": "ECDH-SS+A128KW",
        "x": "7cvYCcdU22WCwW1tZXR8iuzJLWGcd46xfxO1XJs-SPU",
        "y": "DzhJXgz9RI6TseNmwEfLoNVns8UmvONsPzQDop2dKoo",
        "d": "Uqr4fay_qYQykwcNCB2efj_NFaQRRQ-6fHZm763jt5w",
    }
)
pub_key = COSEKey.from_jwk(
    {
        "kty": "EC",
        "crv": "P-256",
        "kid": "[e-mail]",
        "x": "Ze2loSV3wrroKUN_4zhwGhCqo3Xhu1td4QjeQ5wIVR0",
        "y": "HlLtdXARY_f55A3fnzQbPcm6hgr34Mp8p-nuzQCE0Zw",
    }
)
r.apply(enc_key, recipient_key=pub_key, context={"alg": "A128GCM"})
ctx = COSE.new(alg_auto_inclusion=True)
encoded = ctx.encode_and_encrypt(
    b"Hello world!",
    key=enc_key,
    nonce=nonce,
    recipients=[r],
)

# The recipient side:
priv_key = COSEKey.from_jwk(
    {
        "kty": "EC",
        "crv": "P-256",
        "alg": "ECDH-SS+A128KW",
        "kid": "[e-mail]",
        "x": "Ze2loSV3wrroKUN_4zhwGhCqo3Xhu1td4QjeQ5wIVR0",
        "y": "HlLtdXARY_f55A3fnzQbPcm6hgr34Mp8p-nuzQCE0Zw",
        "d": "r_kHyZ-a06rmxM3yESK84r1otSg-aQcVStkRhA-iCM8",
    }
)
assert b"Hello world!" == ctx.decode(encoded, priv_key, context={"alg": "A128GCM"})

COSE Signature1

Create a COSE Signature1 message, verify and decode it as follows:

from cwt import COSE, COSEKey, Signer

# The sender side:
signer = Signer.new(
    cose_key=COSEKey.from_jwk(
        {
            "kty": "EC",
            "kid": "01",
            "crv": "P-256",
            "x": "usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8",
            "y": "IBOL-C3BttVivg-lSreASjpkttcsz-1rb7btKLv8EX4",
            "d": "V8kgd2ZBRuh2dgyVINBUqpPDr7BOMGcF22CQMIUHtNM",
        }
    ),
    protected={"alg": "ES256"},
    unprotected={"kid": "01"},
)
ctx = COSE.new()
encoded = ctx.encode_and_sign(b"Hello world!", signers=[signer])

# The recipient side:
pub_key = COSEKey.from_jwk(
    {
        "kty": "EC",
        "kid": "01",
        "crv": "P-256",
        "x": "usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8",
        "y": "IBOL-C3BttVivg-lSreASjpkttcsz-1rb7btKLv8EX4",
    }
)
assert b"Hello world!" == ctx.decode(encoded, pub_key)

COSE Signature

Create a COSE Signature message, verify and decode it as follows:

from cwt import COSE, COSEKey, Signer

# The sender side:
signer = Signer.new(
    cose_key=COSEKey.from_jwk(
        {
            "kty": "EC",
            "kid": "01",
            "crv": "P-256",
            "x": "usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8",
            "y": "IBOL-C3BttVivg-lSreASjpkttcsz-1rb7btKLv8EX4",
            "d": "V8kgd2ZBRuh2dgyVINBUqpPDr7BOMGcF22CQMIUHtNM",
        }
    ),
    protected={1: -7},
    unprotected={4: b"01"},
)
ctx = COSE.new()
encoded = ctx.encode_and_sign(b"Hello world!", signers=[signer])

# The recipient side:
pub_key = COSEKey.from_jwk(
    {
        "kty": "EC",
        "kid": "01",
        "crv": "P-256",
        "x": "usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8",
        "y": "IBOL-C3BttVivg-lSreASjpkttcsz-1rb7btKLv8EX4",
    }
)
assert b"Hello world!" == ctx.decode(encoded, pub_key)

API Reference

See Document.

Supported CWT Claims

See Document.

Supported COSE Algorithms

See Document.

Referenced Specifications

Python CWT is (partially) compliant with following specifications:

• RFC8152: CBOR Object Signing and Encryption (COSE)
• RFC8230: Using RSA Algorithms with COSE Messages
• RFC8392: CBOR Web Token (CWT)
• RFC8747: Proof-of-Possession Key Semantics for CBOR Web Tokens (CWTs)
• RFC8812: COSE and JOSE Registrations for Web Authentication (WebAuthn) Algorithms

Tests

You can run tests from the project root after cloning with:

$ tox