Shared Device Model
Definition
The scenario in which multiple individuals use the same camera. The PRNU fingerprint links an image to the device, not to any individual user, so device sharing creates an attribution gap between camera and person.
- Scenario
- Multiple individuals using the same camera
- Fingerprint used
- PRNU (photo-response non-uniformity)
- Attribution level
- Links image to device, not to an individual user
- Resulting limitation
- Attribution gap between camera and person
Common questions
Why can't PRNU close the gap between device and person on its own?+
PRNU is a physical sensor artefact fixed to the hardware itself, so it records nothing about who was holding the camera at the time of capture, meaning device sharing has to be resolved through other evidence like custody records or metadata.
What other evidence typically fills the gap PRNU leaves in a shared-device case?+
Investigators often turn to usage logs, witness accounts, timestamps correlated with a suspect's known location, or corroborating digital artefacts on the device to establish who was using it at the relevant time.
Related terms
- Anti-Forensic PRNU Suppression
- Deliberate actions to remove or obscure the PRNU fingerprint, such as adding PRNU-erasing noise, applying heavy lossy compression, or scaling and re-cropping...
- Base Rate Problem
- The statistical challenge facing any deception-detection method: if only a minority of statements examined are actually deceptive, even a method that is...
- Individual vs Device-Class Attribution
- Individual attribution identifies one specific camera body. Device-class attribution identifies only the make or model. PRNU provides individual attribution; metadata and lens-distortion...
- PRNU Suppression
- Any processing that reduces the usable PRNU signal in an image: heavy JPEG compression, resolution downscaling, in-camera noise reduction, social-media re-encoding, and...
- Uncertainty Quantification in PRNU
- Expressing a PRNU attribution result not just as a binary yes/no but with stated PCE values, false-positive rate at the threshold used,...