shamir

This is a simple demonstration of a threshold scheme, using Adi Shamir's secret sharing.

Shamir secret sharing enables us to divide a secret S, into k shares, such that S is reconstructable from a threshold of k pieces, but knowledge of k - 1 reveals nothing about S. Threshold schemes can be used to mitigate the threat of authorized insiders abusing their privileged access to a system, since a malicious insider must compromise a threshold of her colleagues' secret shares, or induce them to collaborate with her, in order to reconstruct S. A common example of this concept in action is the so-called "two man rule" used to control the use of nuclear weapons.

Since the security of Shamir secret sharing is dependent upon no single individual knowing S, it is unfortunate that S remains vulnerable when k shares are generated, as well as when these shares are used to compute S, in order to authorize some action in a computer system. In order to reduce this threat, we can compute S in a Trusted Execution Environment (TEE), using Enarx, which reduces the size of the trusted computing base where S is exposed at secret sharing and reconstruction time.

A description of Enarx's threat model can be found here.

BUILD

To run Shamir in a TEE, first install Enarx and its dependencies.

Compile Shamir to a WebAssembly target:

cargo build --release --target=wasm32-wasi

USAGE

To run Shamir in an Enarx Keep:

enarx run target/wasm32-wasi/release/shamir.wasm

Arguments:

shamir --help
shamir 0.1.0

USAGE:
    shamir --launchcode <LAUNCHCODE>

OPTIONS:
    -h, --help                       Print help information
    -l, --launchcode <LAUNCHCODE>    
    -V, --version                    Print version information