createSigningString.js

export const createSigningString = async (message: string, created?: string, expires?: string) => {
   if (!created) created = Math.floor(new Date().getTime() / 1000).toString();
   if (!expires) expires = (parseInt(created) + (1 * 60 * 60)).toString(); 
   await _sodium.ready;
   const sodium = _sodium;
   const digest = sodium.crypto_generichash(64, sodium.from_string(message));
   const digest_base64 = sodium.to_base64(digest, base64_variants.ORIGINAL);
   const signing_string =
       `(created): ${created}
(expires): ${expires}
digest: BLAKE-512=${digest_base64}`
   return { signing_string, expires, created }