The libsignal extension module provides cryptographic functions for Hydra/DGD, required for signal-server.

Building requires OpenSSL 1.1.1 or later and a side-by-side git checkout of the standard DGD extension modules. Build those first, and then build the libsignal module with make in libsignal/src. The libsignal module will be placed in the lpc-ext top directory.