libgfshare-bin

This library implements what is known as Shamir Secret Sharing. This entails encoding a secret as an integer and then constructing a polynomial whose coefficients are random and calculating coordinate pairs along the resultant curve. These coordinate pairs are considered 'shares' and by controlling the order of the polynomial we can control the number of shares required to be able to recover the secret.

In this manner we can split a secret into any 'C' shares, any 'T' of which can be used to recover the secret.

This would be useful, for example, in looking after GPG secret keys used rarely, but whose security is paramount. For example a key used to sign the key which signs the Debian or Ubuntu package archives.

If you wish to know more about how the secret sharing works and why it is safe, there exists many articles on the mathematics behind it.

This particular implementation was very heavily inspired by the work of Mark D. Wooding (mdw) in his catacomb library. Thanks go to Mark for offering to share this implementation with me.

Using the library is very easy. The tests and sample tools are very straightforward and the header file tells you what each function is used for.