GnuTLS

GnuTLS (ˈɡnuː_ˌtiː_ˌɛl_ˈɛs, the GNU Transport Layer Security Library) is a free software implementation of the TLS, SSL and DTLS protocols. It offers an application programming interface (API) for applications to enable secure communication over the network transport layer, as well as interfaces to access X.509, PKCS #12, OpenPGP and other structures. GnuTLS consists of a library that allows client applications to start secure sessions using the available protocols. It also provides command-line tools, including an X.509 certificate manager, a test client and server, and random key and password generators. GnuTLS has the following features: TLS 1.3, TLS 1.2, TLS 1.1, TLS 1.0, and SSL 3.0 protocols Datagram TLS (DTLS) 1.2, and DTLS 1.0, protocols TLS-SRP: Secure remote password protocol (SRP) for TLS authentication TLS-PSK: Pre-shared key (PSK) for TLS authentication X.509 and OpenPGP certificate handling CPU assisted cryptography and cryptographic accelerator support (/dev/crypto), VIA PadLock and AES-NI instruction sets Support for smart cards and for hardware security modules Storage of cryptographic keys in the system's Trusted Platform Module (TPM) GnuTLS was initially created around March to November 2000, by Nikos Mavrogiannopoulos 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; thus software under the GPL, such as GNU software, could not use OpenSSL without making a GPL linking exception. The GnuTLS library was licensed originally under the GNU Lesser General Public License v2, while included applications to use the GNU General Public License. In August 2011 the library was updated to the LGPLv3. After it was noticed that there were new license compatibility problems introduced, especially with other free software with the license change, after discussions the license was downgraded again to LGPLv2.1 in March 2013.