ext/ -> Implementation of TLS extensions

auth/ -> Implementation of TLS authentication methods (DHE, SRP etc.)

accelerated/ -> Implementation of cipher acceleration

Certificate support:

x509/ -> Implementation of GnuTLS X.509 certificate support (and more)

openpgp/ -> Implementation of GnuTLS openpgp support

opencdk/ -> Implementation of low level openpgp packet parsing

minitasn1 -> ASN.1 structure parsing library

Crypto backends:

nettle/ -> -> The nettle crypto back-end

gcrypt/ -> -> The libgcrypt crypto back-end