verify = function(hashbuf, sig, pubkey, opts) {
  if (!pubkey) {
    throw new Error('pubkey required for signature verification');
  }
  pubkey = new PublicKey(pubkey);
  
  if (!sig) {
    throw new Error('signature required for verification');
  }
  sig = new Signature(sig);

  return !verificationError(hashbuf, sig, pubkey, opts);
}
Verify a signature
@param {Buffer} hashbuf
@param {Signature} sig
@param {PublicKey} pubkey
@param {Object|undefined} opts An object of optional parameters
@param {String} opts.endian 'big' or 'little' (default: big)
@returns {Boolean}