Hash To Curve With Cloudflare CIRCL
One of the great advancements with the Internet has been RFC (Request For Comment) documents and Internet Engineering Task Force (IETF) Internet-Drafts. The classics of such as RFC791 (IPv6) and RFC793 (TCP) brought a level of conformity that broke the dominance of large companies and countries in defining standards.
A new Internet-Draft [here] brings a new standardization for hashing data values into curves. This can be in the form of hashing a value to a scalar — which might then be used to multiply a point — or onto a curve:
Its importance is due to the increasing usage of elliptic curve methods and their application into zero-knowledge proofs (ZKPs) and multiparty computation (MPC).
For the hashing of our data to a scalar, we use the ExpandMessageXmd function. This produces a uniformly random byte string using a cryptographic hash function H() that outputs b bits. Overall we typically use SHA-256 or SHA-512 for the hashing function. As an input, we use a message string and a DST string. The method defined [here]:
expand_message_xmd(msg, DST, len_in_bytes) Parameters:
- H, a hash function (see requirements above).
- b_in_bytes…
