[Cryptography-dev] Loading a Curve25519 X.509 key

[Alex Gaynor]

Hi Saruabh,

I think https://cryptography.io/en/latest/hazmat/primitives/asymmetric/serialization.html#cryptography.hazmat.primitives.serialization.load_pem_public_key
should work. Notwithstanding the docs, I believe it'll load an
X25519PublicKey :-) If that works for you, let us know and I'll make
sure we fix those docs.

Alex

On Wed, Mar 10, 2021 at 11:56 AM Saurabh Kapoor <saurabh at fintify.com> wrote:
>
> Hi,
>
> A service we communicate with sends us their Curve25519 public key as a PEM file. The key is DER encoded and the format is X.509's SubjectPublicKeyInfo.
>
> We would like to create a cryptography.hazmat.primitives.asymmetric.x25519.X25519PublicKey for this object but I am unable to find the routines to load such keys. X25519PublicKey.load_public_bytes(..) expects a raw key.
>
> Using the following openssl command I can examine the key: openssl asn1parse -in pub_key.pem
>
> Any suggestions on how my service written in Python can load this kind of a public key? I've also posted a slightly more detailed question here: https://stackoverflow.com/questions/66492939/python-decoding-an-ecdh-curve-25519-public-key-encoded-as-a-pem-file
>
> regards,
> Saurabh
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