Function hkdfExtract

src/utils/nip44.ts:8–10

(salt: Buffer, ikm: Buffer)

// HKDF-extract: PRK = HMAC-SHA256(salt, IKM)
function hkdfExtract(salt: Buffer, ikm: Buffer): Buffer {
  return createHmac('sha256', salt).update(ikm).digest()
}

// HKDF-expand: OKM = T(1) || T(2) || ... where T(n) = HMAC-SHA256(PRK, T(n-1) || info || n)
function hkdfExpand(prk: Buffer, info: Buffer, length: number): Buffer {