def requires_auth(f):
    """
    Determines if the Access Token is valid
    """
    @wraps(f)
    def decorated(*args, **kwargs):
        token = get_token_auth_header()
        jsonurl = urlopen("https://"+AUTH0_DOMAIN+"/.well-known/jwks.json")
        jwks = json.loads(jsonurl.read())
        unverified_header = jwt.get_unverified_header(token)
        rsa_key = {}
        for key in jwks["keys"]:
            if key["kid"] == unverified_header["kid"]:
                rsa_key = {
                    "kty": key["kty"],
                    "kid": key["kid"],
                    "use": key["use"],
                    "n": key["n"],
                    "e": key["e"]
                }
        if rsa_key:
            try:
                jwt.decode(
                    token,
                    jwt.algorithms.RSAAlgorithm.from_jwk(json.dumps(rsa_key)),
                    algorithms=ALGORITHMS,
                    audience=API_AUDIENCE,
                    issuer="https://"+AUTH0_DOMAIN+"/"
                )
            except jwt.ExpiredSignatureError:
                raise AuthError({"code": "token_expired",
                                 "description": "token is expired"}, 401)
            except (jwt.InvalidAudienceError, jwt.InvalidIssuerError):
                raise AuthError({"code": "invalid_claims",
                                 "description": "incorrect claims, please check the audience and issuer"}, 401)
            except Exception:
                raise AuthError({"code": "invalid_header",
                                 "description": "Unable to parse authentication token."}, 401)

            return f(*args, **kwargs)
        raise AuthError({"code": "invalid_header",
                         "description": "Unable to find appropriate key"}, 401)
    return decorated