SILC is an open, security-focused end-to-end encrypted protocol. Its website is currently hosted at silc.github.io.
You need to install the SILC Toolkit and the libpurple SILC plugin. These were
generally provided as packages in several Linux distributions, however, many
distributions have begun dropping these packages due to being “unmaintained.”
If you’re compiling Pidgin and libpurple yourself, see the ./configure --help
for specifying the location of the SILC headers and libraries. If you’re
compiling with an SRPM, use --with-silc to build the purple-silc RPM
On Windows, the SILC Toolkit is installed with Pidgin.