(lib)sss

Toy implementation of Shamir's Secret Sharing.

Quickstart

make
./sss

Up to 32 characters (ASCII) will be read from stdin - use CTRL-D (twice if not after a newline) to end input. Your input will be split into three pieces (share1, share2 and share3), any two of which can be used to reconstruct it.

To recover the secret use

./sss -d

which is a shortcut for ./sss -d share1 share2.

Run ./sss -h for more info or make install to install.

Development notes

This repo includes two main components:

• secret sharing functionality in a library libsss
• a program to encode and decode secrets using said library, sss.

By default, the library is only built and installed as a static archive. On macOS it can also be built as a dylib by running make mac instead of just make. You can then make install as normal.

Running make test will run some basic tests against the library via the sss program.

Current limitations

• the demo program sss can only generate up to nine shares (the library has no such constraints)
• secrets must be 32 bytes - smaller secrets will be right-padded with zero-bytes
• only supports an install prefix of /usr/local
• only supported on unix-like OSes

Dependencies

• C compiler and make
• The GNU Multiple Precision Arithmetic Library - tested with version 6.3.0
• xxd - for tests only
• clang-format - for formatting only