It uses <a href="https:&#x2F;&#x2F;cryptography.io&#x2F;en&#x2F;latest&#x2F;" rel="nofollow">https:&#x2F;&#x2F;cryptography.io&#x2F;en&#x2F;latest&#x2F;</a> , the origin of which is described at <a href="https:&#x2F;&#x2F;lwn.net&#x2F;Articles&#x2F;595790&#x2F;" rel="nofollow">https:&#x2F;&#x2F;lwn.net&#x2F;Articles&#x2F;595790&#x2F;</a> . Under the hood that uses OpenSSL.