This is an implementation of the ECDH over P-256 key exchange algorithm, using code from Fiat (https://github.com/mit-plv/fiat-crypto).
Cryptographic primitives should not be used in end applications, they are better used as part of a cryptographic library.
Published: 03 Nov 2020
fiat-p256 contains primitives for ECDH key exchange algorithm over NIST curve P-256.
It internally uses bindings to C code generated using the correct-by-construction implementations from fiat-crypto.
Please be aware that cryptographic primitives should not be used in end applications, they are better used as part of a higher level cryptographic library.
fiat-p256 is available on opam and can be install as follows:
opam install fiat-p256
The entry point to this library is the
Fiat_p256 module and the main function is
dh which let you perform a key exchange given your private key
scalar and the other party's public key
let secret = Fiat_p256.dh ~scalar ~point
Note that the
point values built or parsed using
Fiat_p256's interface are checked according to NIST's Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography section 22.214.171.124.2 so that you shouldn't be able to provide an invalid point or the point at infinity to the functions exposed in this module.
You can also compute the public P-256 key corresponding to your private key
scalar using the
let public_key = Fiat_p256.public ~scalar
Note that the
scalar values parsed using
Fiat_p256's interface must be within P-256's generator subgroup order range so that your public key can't be the point at infinity. Any scalar not in the range
[1 - (n-1)],
n being the group order, will be rejected.