Originally Posted by
Grog
I'm starting to follow the money on this subject. It's sounding like "it's all about a barcode" and the industry involved in producing them.
There's no "industry" in barcodes. The IATA makes the barcode format
an open standard. Paper boarding passes use a
PDF417 format barcode while mobile barcodes can be in the formats of
Aztec codes,
Datamatrix, or
QR Codes. All of these have freeware to read on PCs and mobile phones, and it's trivial to generate them on PCs as well with freeware. This is part of the problem with their security. To counter this, particularly when travelers are subject to expedited screening, they digitally sign them. Using the private key of the issuer (the airline) the boarding pass is signed. Using the public key that corresponds (the TSA puts it into their boarding pass scanners), the TSA can validate that the boarding pass has not been changed since the airline issued it.
Foreign airlines could easily get Precheck by doing three things:
1) Including the Known Traveler Number in their ticketing information so this information is available for TSA Secure Flight Consideration;
2) Creating a mechanism to receive the information on whether or not the traveler is Precheck eligible from the TSA;
3) Digitally signing boarding passes at generation and providing the public key to the TSA so the TSA ID scanners can validate whether a boarding pass has been altered after the TSA.
Ostensibly because foreign carriers primarily operate flights outside of the US, other than Canadian carriers (not a majority but certainly substantial portions go to the US), they have not bothered with this integration effort. There is no one charging the airlines to digitally sign their boarding passes (I could generate a strong private/public keypair on my computer in less than a minute). The barcodes are based on open standards and require no licensing; regardless, over 200 airlines are already making these barcodes, they just need to digitally sign them.
Originally Posted by
SchmeckFlyer
Using this argument, every single government-issued form of identification is suspect as passports and so forth can be counterfeited, meaning every time a person wishes to travel would require a unique document with a unique barcode be generated. Additionally, if we assume GE cards and passports can be easily counterfeited, the entire security process (including generating barcodes for boarding cards) falls flat on its face as a bedrock of security is being able to verify security, using identity documents (including GE cards).
The TSA has offered an $80M deal for technology that will both validate whether or not an ID is counterfeit, whether or not a boarding pass is counterfeit, and a cross compare (automatically) that the two match (e.g. not different names). Some documents from 2014 say they were looking to start testing at airports in late 2015, but I haven't seen it or heard more so I'm sure it was delayed (they started looking to get this technology rolling in 2011).
Originally Posted by
SchmeckFlyer
I also imagine anyone with a printer and some technical expertise could counterfeit a boarding card.
A concern which was brought up for years (the information printed on the surface is obvious, and the information on what fields and field lengths constitute the boarding pass barcode are entirely open*), and one of the reasons that digital signing of boarding passes started by major US airlines (alterations of the boarding pass would result in the signature not matching, causing rejection by the boarding pass scanner). I don't know if you've ever been in the scenario to see the TSO's side of the Desko Penta scanners they use, but they explicitly state whether or not a digital signature on a boarding pass is valid after they scan it, along with the name and some other information.
Originally Posted by
SchmeckFlyer
I do now understand that apparently using Pre is subject to approval every single time one boards a flight. Of this I was not aware. I fail to understand why this is the case, and fail to understand why the TSA cannot itself provide authorisation on the spot (if algorithms are used) regardless of airline used.
Do not attempt to understand the bureaucracy. I've received Pre 100% since receiving GE, but the first time I went to use it in 2013 (printed on boarding pass) I was deferred to the regular line I expressed disappointment to the TSO that it was my first opportunity and he said
Go, I'll just defer the next guy 
)
I have seen several anecdotes on different forums that going to certain locations may trigger either SSSS or just a lack of Pre for a while despite GE/Nexus. Particularly, I've seen a few threads where people say they stopped getting Pre after visiting Turkey. Anecdotal, I know...