The CBOE Nasdaq Volatility Index (VXN) is a measure of market expectations of 30-day volatility for the Nasdaq-100 index, as implied by the price of options on this index. What is VXN? Definition of VXN. The VIX is based on the implied volatility of options on stocks included in the S&P 500 Index. What does VXN: AuthenticationError mean? "VXN: AuthenticationError" is the message generated by First Data Secure Transport (aka Datawire) when there is an. The Cboe NASDAQ-100 Volatility IndexSM (VXN) is a key measure of market expectations of near-term volatility conveyed by NASDAQ-100® Index (NDX). The CBOE NASDAQ Volatility Index (VXN) is a measure of market expectations of near-term volatility conveyed by NASDAQ-100 Index (NDX) options prices.