sha256.js

function generateAuthenticationString(password, salt, challenge) {
  const step1 = password + salt;
  const step2 = sha256(step1); // SHA256 binary hash

  const base64Secret = Buffer.from(step2, 'hex').toString('base64');
  
  const step3 = base64Secret + challenge;
  const step4 = sha256(step3); // SHA256 binary hash
  
  const authenticationString = Buffer.from(step4, 'hex').toString('base64');
  
  return authenticationString;
}