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GnuTLS ( /ˈɡnuː ˌtiː ˌɛl ˈɛs/, the GNU Transport Layer Security Library) is a free software implementation of the SSL, TLS and DTLS protocols. It offers an application programming interface (API) for applications to enable secure communication over their network transport layer, as well as interfaces to access X.509, PKCS #12, OpenPGP and other structures.

Features [link]

GnuTLS consists of a library that allows client applications to start secure sessions using the available protocols, as well as of a few command-line tools, including an X.509 certificate manager, test client and server, random key and password generators. As of 2011^[update] Apache can be configured to use GnuTLS so as to support TLS 1.2.^[3]

GnuTLS has the following features:

• SSL 3.0, TLS 1.0, TLS 1.1 protocols and the current TLS 1.2 protocol
• Datagram TLS (DTLS) 1.0
• Secure remote password protocol (SRP) for TLS authentication
• Pre-shared key (PSK) for TLS authentication
• X.509 and OpenPGP certificate^[4] handling
• CPU assisted cryptography and cryptographic accelerator support (/dev/crypto only, no AF_ALG)
• Support for smart cards and for hardware security modules

License and motivation [link]

The GnuTLS library is licensed under the GNU Lesser General Public License; included applications are licensed under the GNU General Public License.

GnuTLS was initially created to allow applications of the GNU project to use secure protocols such as TLS. Although OpenSSL already existed, OpenSSL's license is not compatible with the GPL;^[5] thus software under the GPL, such as GNU software, could not use OpenSSL without making a GPL linking exception.

The list of software packages using GnuTLS includes GNOME, CenterIM, Exim, Weechat, Mutt, slrn, Lynx, CUPS and gnoMint.^[6]

See also [link]

	Free software portal
	Cryptography portal

• CyaSSL
• OpenSSL
• PolarSSL
• Network Security Services
• Comparison of TLS Implementations
• Transport Layer Security

References [link]

External links [link]

• Official website
• A 2003 interview with GnuTLS primary author Nikos Mavrogiannopoulos
• A 2009 interview with GnuTLS maintainer Simon Josefsson

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