Drudge has picked up this story.

@baliktad...true that a TSO can direct a person for additional screening even without any audible alarms indicating the person needs additional screening

However, if a person has the 3 beeps - which is generally believed to indicate approval for precheck, do you really think a TSO will "get away" with not allowing that person into precheck?

The purpose of not knowing your status was to make precheck authorization unpredictable - this is meant to discourage prechecker (allegedly we the American People can trust precheckers) from bringing items that are not allowed.

Knowing your status before you even pack your luggage, allows a prechecker to do exactly what TSA was trying to discourage by way of not letting the prechecker know till the airport.

So yes, not a garuntee even with authorization, likelyhood a TSO will deny you access to precheck - when the TSO, you, and everyone else in precheck knows you are approved for it - very very small.

Yes, TSO's routinely tell people to do whatever they want.

But more importantly, the response of the barcode reader is still fully in control of the TSA. Right now everyone assumes that a 3 on the barcode means LLL, 3 beeps, and expedited screening 100% of the time. This is an assumption made without a full understanding of the system. The barcode reader can still beep once even when a 3 is present in the barcode.

Even with an electronic signature, that won't stop people from trying to find workarounds, or ways to mess around with/otherwise exploit - that's what makes fields of work/study dedicated to such things incredibly fun to consider going into.

And note that even those programmers who don't focus on such matters still need to pay attention to them--if you don't understand how people might break your stuff you can't hope to make it so they can't break it.

This person tweeted their AA boarding pass back in April 2010. I decoded this using my old Windows Mobile 6.5 phone using an app.

http://bit.ly/SNhryv

Knowing that all AA tickets start with 001 I thought that the last 14 digits prior to the "AA AA" Advantage number was the ticket number plus a check digit. In this case it's zero. Are we now saying that it's 3 if you are pre selected for PreCheck?

Exactly.

IMO, Ari is a bit hasty in dismissing people in the manner done in the post I repled to.

Exactly. For a data point I checked the last 3 of my US Airways boarding passes that allowed for precheck and there was no 3 in there.

Without the 3 in the barcode, how did the offline scanner know to indicate LLL?

I haven't been able to figure the pattern out since I don't have enough passes to scan and compare yet but I can tell you that it's definitely not dependent on the number 3 at the end of the sequence.

For US Airways, it is the second-to-last number in the long sequence that counts. The last number is something else-- the API indicator. You want the selectee indicator which comes before the API indicator. Most domestic boarding passes will leave the API indicator blank, but not on US.

Sure enough that's it ! Thanks for the tip.