libtls is part of libressl:
http://www.libressl.org/> LibreSSL is composed of four parts:
> The openssl(1) utility, which provides tools for managing keys, certificates, etc.
> libcrypto: a library of cryptography fundamentals
> libssl: a TLS library, backwards-compatible with OpenSSL
> libtls: a new TLS library, designed to make it easier to write foolproof applications