Encoding with RSA public key and decoding with private key

In the documentation it says:

When using the RSASSA-PKCS1-v1_5 algorithms, the key argument in both jwt.encode() and jwt.decode() (“secret” in the examples) is expected to be either an RSA public or private key in PEM format.

When i try to encode the payload with the public key i get an error:

>>> jwt_message = jwt.encode(payload, pub_rsakey, 'RS384')
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/Users/sven/code/sso/env/lib/python2.7/site-packages/jwt/__init__.py",
 line 295, in encode
    signature = signing_methods[algorithm](signing_input, key)
  File "/Users/sven/code/sso/env/lib/python2.7/site-packages/jwt/__init__.py",
 line 131, in <lambda>
    'RS384': lambda msg, key: sign_rsa(msg, key, hashes.SHA384()),
  File "/Users/sven/code/sso/env/lib/python2.7/site-packages/jwt/__init__.py",
 line 106, in sign_rsa
    signer = key.signer(
AttributeError: '_RSAPublicKey' object has no attribute 'signer'

What is happening is that the implementation in algorithms.py, line 137 tries to sign with the public key, but the cryptography.hazmat.backends.openssl.rsa._RSAPublicKey has no signer method: https://cryptography.io/en/latest/hazmat/primitives/interfaces/#cryptography.hazmat.primitives.interfaces.RSAPublicKey

[svnv]

So, it looks like I misunderstood how jwt works. I somehow thought that the payload was also encrypted with the RSA key. (I edited my previous post in light of my new knowledge.)

The documentation should at least be updated to reflect that encoding (signing) is only possible with a private RSA key and decoding (verification) only works with a public key.

[jpadilla]

Closed via #88