We've recently implemented WS Trust security over SSL for our client / server communications. Our application is used by thousands of our customers, spread out all over the world. One of the problems we've had in the past with secure communications is that customers with unsynchronized clocks have difficulty connecting, resulting in customer calls and frustration. Unfortunately, the reaction that has caused in the past is to simply disable this check or simply increase the acceptable clock skew to near infinite amounts.
I do not want the security of our system to be compromised, nor do I want to trigger an influx of complaints of customers who do not have their clocks closely in sync with the time on our servers (which are synced to internet time). In order for me to prevent the synchronization check from effectively being disabled, I must first be able to explain to my managers why this is a bad idea, and why the benefits of clock synchronization outweigh the cost of customer complaints or confusion.
- What role does clock synchronization play in SSL communications and what sorts of vulnerabilities does disabling it introduce?
- What is typically considered to be the maximum acceptable range for clock synchronization in secure customer facing applications?