[dalai]

One could ask whether python would have been an option for writing the parser. There is for example the asn1crypto library, which is pure python.

[xxpor]

I'd have to assume the issue there is really speed.

Edit: @alex made a much better comment here:

https://github.com/pyca/cryptography/issues/5771#issuecommen...

One point that I didn't think of, but makes a ton of sense:

>There's no way to implement constant-time code in pure Python securely