According to Reuters, Apple paid a premium of about 58 percent for the Melbourne, Fla.-based company, or about $8 per share.

So what is AuthenTec? Even if you’ve never heard of the company, many of Apple’s competitors — who are AuthenTec customers and partners — have.

AuthenTec makes fingerprint sensors that can authenticate access to mobile devices and PCs. The company says 100 million of its sensors have already been shipped and they’re in more than 20 million phones. It counts HP, LG, Motorola (now owned by Google), Nokia and Samsung as just a few of its customers.

As for why Apple would be interested in such a company, well, mobile security is obviously important. Apple may be eyeing fingerprint-based authentication for iPhones and MacBooks. Or maybe it’s interested in AuthenTec’s NFC-payment security technology for a future iPhone with mobile payment capabilities? Another asset AuthenTec has is a patent portfolio — it has 200 technology patents that are “foundational” to fingerprint biometrics.

A $356 million purchase is certainly small for a company as rich as Apple (it has $117 billion in the bank) but it falls in line with the company’s history of purchasing smaller firms. Most of Apple’s acquisitions tend to be software-based. But it’s been thinking hardware in recent months: At the end of 2011, it bought Israel-based flash memory maker Anobit. Along with earlier hardware acquisitions – it bought Intrinsity, which works on designing chips to run faster, in 2010; and in 2008 it acquired P.A. Semi, the company brought in to design Apple’s custom iPhone and iPad chips — Anobit and AuthenTec fit with Apple’s belief in controlling as many aspects of its products as possible, from the operating system down to the chips.

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