2 library(ssl): Secure Socket Layer (SSL) library
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Availability::- use_module(library(ssl)).(can be autoloaded)
Source[semidet]ssl_peer_certificate(+Stream, -Certificate)
True if the peer certificate is provided (this is always the case for a client connection) and Certificate unifies with the peer certificate. The example below uses this to obtain the Common Name of the peer after establishing an https client connection: 
  http_open(HTTPS_url, In, []),
  ssl_peer_certificate(In, Cert),
  memberchk(subject(Subject), Cert),
  memberchk('CN' = CommonName), Subject)