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Digital Video Authenticator

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What can it do?

Use of the DVA with chain-of-custody records and a public key infrastructure will generate the “preponderance of evidence” needed to authenticate digital video. The method detects modified frames, whether the modifications are intentional or unintentional. Subsequent analysis of modified frames can distinguish intentional edits from camcorder- and tape-drive-generated errors. Digital signatures are generated in real time as the video is recorded, and all private keys are then immediately destroyed to eliminate the possibility of tampering afterward. Public key management within a Government-off-the-shelf public key infrastructure will provide the chain of custody needed to demonstrate positive control of the evidence. Questions about the reliability of the digital video can be answered with irrefutable, non-forgeable evidence collected at the same instant that the digital video was made.

Ensuring the integrity of digital video (DV) evidence involves secure storage and chain-of-custody records, collecting digital video with the simultaneous frame-by-frame digital signatures, and safeguarding of public and private keys.

Digital signatures are a widely accepted method of ensuring data integrity. The signature is a short abbreviation of the message encrypted via public-key cryptography. The private key is used to encrypt the data, and the public key is used to decrypt it. The private key is embedded in the DVA and is inaccessible to external devices. It is used to generate digital signatures in real time and destroyed immediately after the video is completed. The public key is signed by to a security token to tie the identity of the law enforcement agent to the video for use in the integrity verification process.

In verification testing, the forensic analysis based on digital signatures identified intentional modifications to the digital video and distinguished them from camcorder- and tape-drive-generated errors. The system detected all single- and multiple-bit alterations and all alterations due to inserted images and recompression. Tape failures showed up as verification errors and were identified either as camcorder-duplicated data interface blocks from previous frames or as camcorder-generated data.

The DVA identifies alterations in the digital video. Here, the audio waveforms from an unaltered frame (left) are compared with a frame that has verification errors (right). The camcorder inserted a square wave into the left frame because of a tape failure.


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