Apple is in the final stages of purchasing a fingerprint security firm – meaning future iPhones are likely to have an extra layer of built-in security.

There are even suggestions that iPhone 5- due to be unveiled on Wednesday – will already have a fingerprint scanner built in, stopping anyone from reading your messages and data without your fingerprint authorization.

If AuthenTec agrees to the $365 million purchase by Apple on October 4, it will be one of the largest sums paid in a takeover by the tech giant.

Other than the purchase of a “flash memory” supplier last year, this is believed to be Apple’s biggest acquisition since the pre-iPod days of 1997, showing how serious Apple is about the technology.

Apple is also unveiling a new service called PassBook, which allows users to store shop coupons, loyalty cards and other items such as airport boarding passes, with the release of iOS6 – the sixth-generation of its iPhone software – this autumn.

Airlines in the U.S., such as United Airlines, American Airlines, Delta Air Lines and Virgin Australia will all allow Apple users to store their documents on their phone, meaning a quick swipe will get you to the boarding gates.

Apple is in the final stages of purchasing a fingerprint security firm meaning future iPhones are likely to have an extra layer of built-in security

AuthentTec creates mobile phone security and, according to the merger documents, has already been developing 2D fingerprint sensors for Apple.

The technology could see a fingerprint scanner built behind the screen, requiring your thumbprint to unlock the phone, or it could be a sensor on the back of the device, across which you roll your thumb to allow access.

Technology writer Matt Brian, for the site My Next Web, said: “Will we see fingerprint technology in the new iPhone, or iPad? It seems almost certain.

“Details are scarce but [Apple’s] desire to use the technology and see it developed quickly leads us to speculate that we could see it in just a matter of weeks.”

If Apple comes with NFC, which allows contactless authorization or payments, it could make the iPhone a wallet-replacements, allowing secure payments for small orders.

The technology is similar to that seen on some bank cards.

However, not everyone agreed that the iPhone 5 will come with either finger-print scanners or NFC technology built-in.

Blogger Sonny Dickson, inspecting images of the insides of the iPhone 5, said the internals do not match the rumors.

Previous looks at the internals revealed a mysterious square that seemed an appropriate candidate for an NFC chip.

But Sonny Dickson said the square may simply hold the front-facing FaceTime camera, proximity sensor and a speaker.

He said: “The latest leaked pictures appear to show that there is indeed no NFC chip or fingerprint scanner included in what appears to be the complete front assembly.

“Apple may well be keeping these features under lock and key until their announcement on September 12th.”

He added that an NFC chip and a fingerprint scanner would make “perfect sense”, but added: “Looking at Apple and their incremental iPhone updates it may be too big an update in too short an amount of time.”

Either way, if NFC does not come to the iPhone this time round, it cannot be far away.

AuthenTec executive Art Stewart said recently: “The real sweet spot for today’s smart sensor is the NFC-enabled smartphone, where the smart sensor not only strengthens security but greatly increases the speed and convenience of mobile payment transactions.

“It accomplishes this by reducing multiple steps into one simple user action.”

If the technology does not appear on the iPhone 5, it is likely to appear on the mooted iPad 4 next spring, or in Apple’s annual refresh of the iPhone next autumn.