♻️BLS Key Generation

The key derivation process allows for the derivation of a child key from a set of intermediate Lamport keys. The entropy source for Lamport private keys is the parent node’s private key, and hashing into compressed Lamport public keys which are hashed into BLS12-381 private key group.

Define the following conventions:

K = 32 is the digest size (in octets) of the hash function (SHA256), L = K * 255 is the HKDF output size (in octets), ‘’ is the empty string,

bytes_split is a function takes in an octet string and splits it into K-byte chunks which are returned as an array

Using the RFC 5869 - HMAC-based Extract-and-Expand Key Derivation Function (HKDF) definition (https://datatracker.ietf.org/doc/html/rfc5869) of Extract and Expand: