SSSS is very simple. The premise of it is that someone has a message that they want to share, but they want to spread it around so it can't all be taken out in one go, just like Horcruxes from Harry Potter. The problem is, is that in today's world there might be great ways to encrypt messages, but there hasn't been any significant development n proper message splitting techniques. That's where Adi Shamir, co-creator of RSA came in.
The way SSSS works is that any small string of characters (not big enough for a file, but fine for a password), gets split into n shares, which have a threshold of t. What this means is that:
my secret root password
When t = 3 and n = 5, will get split into:
1-1c41ef496eccfbeba439714085df8437236298da8dd824 2-fbc74a03a50e14ab406c225afb5f45c40ae11976d2b665 3-fa1c3a9c6df8af0779c36de6c33f6e36e989d0e0b91309 4-468de7d6eb36674c9cf008c8e8fc8c566537ad6301eb9e 5-4756974923c0dce0a55f4774d09ca7a4865f64f56a4ee0
With this, we only need t shares to complete the secret. So, if I give out 5 shares of my password to people, but I have a threshold of 3, only 3 people will need to meet up to determine my password. This can be dangerous and useful at the same time.
SSSS is not particularly popular, thus there is currently only one implementation available. You can get it as a debian package, and it's also available through the Arch User Repository. The SSSS website is here.