How It Works - HP iPAQ h5400 Series White Paper
Biometric security
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Also See for iPAQ h5400 Series:
- Reference manual (273 pages) ,
- Specification (13 pages) ,
- Specifications (12 pages)
biometric security with the iPAQ Pocket PC h5400 series
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how it works
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Biometric security on your iPAQ Pocket PC works in two basic steps: fingerprint enrollment and
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fingerprint verification. Fingerprint enrollment involves fingerprint acquisition and image
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reconstruction, fingerprint image processing and feature extraction, fingerprint image quality
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evaluation, and template generation. Fingerprint verification involves fingerprint acquisition and
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image reconstruction, fingerprint image processing and feature extraction, fingerprint image
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quality evaluation, template generation, and template matching.
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enrollment
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Enrollment is the process of collecting, processing, and registering reference versions of the
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fingerprints of the person authorized to use the secured device, in this case, the iPAQ Pocket PC.
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This is the initial step. The user is guided through the process for selecting one or more fingers to
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enroll and swiping the selected fingers across the FingerChip sensor to capture associated
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fingerprint images. Enrollment assesses the quality of the captured images and directs the user, as
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required, to repeat the swiping activity until adequate images are obtained. This process may
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require several attempts to ensure good prints are captured. A dataset is extracted from the images
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for each finger enrolled. These datasets are the reference templates used to ensure that only the
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authorized user is allowed to logon to your iPAQ Pocket PC during verification. The iPAQ Pocket
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PC enrollment process includes user training designed to teach proper swiping of fingers across
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the FingerChip sensor.
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These templates are stored locally on the iPAQ Pocket PC (in a BioSwipe.dat file) and are
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encrypted. The file is only decrypted when used by the BioSwipe software. Template coding is a
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Cogent private format. Only Cogent software can read and use the template data. The encryption
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code is also private. Only BioSwipe or Cogent software can decrypt the data.
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verification
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Verification is the process of collecting, processing, and comparing a person's fingerprint with the
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fingerprints on record to confirm identification or deny access. Based on the designated
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authentication mode, the user will swipe an enrolled finger across the FingerChip sensor to capture
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the associated fingerprint image. Verification assesses the quality of the captured image and, if
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necessary, directs the user, to repeat the swiping activity to ensure that a good quality image is
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obtained. A dataset is extracted from the fingerprint, designated the sample template. The sample
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template is matched against the reference templates stored on your iPAQ Pocket PC. The result of
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the match is used by Pocket PC authentication to permit or deny access as appropriate.
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As noted, there are several sub-processes, many of which are common, that support enrollment and
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verification. The next sections describe these sub-processes.
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fingerprint acquisition and image reconstruction
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As mentioned earlier, scanned thermal imaging works because the fingerprint is made up of ridges
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and valleys that each emits different thermal readings. Pyro-electric material converts the
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differences in these temperatures into corresponding voltages. Since fingerprints are unique, so to
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are the voltages that are derived from them.
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The question now becomes how best to capture this thermal fingerprint image? The process that
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works best for this image capture is known as image scanning. With this process, a rectangular
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window (with a width the size of a finger) is used. The fingertip is swept vertically over this sensor
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window and the image is recorded in sections and then reconstructed by software.
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Fingerprint acquisition and image reconstruction is used for both enrollment and verification.
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