topic 6 - forensic camera identification - sensor pattern noise Flashcards
what is the criminal offences and the law behind digital images?
Photography of certain subject matter is restricted in the United Kingdom. In particular, the Protection of Children Act 1978 restricts making child pornography or what looks like child pornography.
It is an offence under the Counter-Terrorism Act 2008 to publish or communicate a photograph of a constable a member of the armed forces, or a member of the security services, which is of a kind likely to be useful to a person committing or preparing an act of terrorism.
what is the criminal offences and the law behind digital images? pt 2
It is also an offence under section 58 of the Terrorism Act 2000 to take a photograph of a kind likely to be useful to a person committing or preparing an act of terrorism, or possessing such a photograph.
it is a criminal offence (contempt) to take a photograph in any court of any person, being a judge of the court or a juror or a witness in or a party to any proceedings before the court, whether civil or criminal, or to publish such a photograph.
what is shot noise?
Shot Noise: Is due, in part, to the random fluctuations in photon energy captured by the image sensor. These variations are recorded in the image as visible noise.
what is readout noise?
Readout Noise: Is electrical charge built up within the camera from the different onboard processes, which leaves random noise within the image.
Both shot noise and readout noise are random additive noise.
what is DSNU?
dark signal non uniformity
DSNU: fixed pattern noise due to dark currents that occur in the sensor even when no light is incident upon it. easy to remove with dark frame subtraction.
what is PRNU?
Photo response non uniformity
PRNU: is the variation in pixel sensitivity caused by manufacturing defects and the natural uniformity of the silicon used in the image sensor.
how is PRNU pattern noise utilised in photo forensics?
The pattern noise caused by the PRNU is consistent, and unique to the image sensor (and therefore the camera) and can be used to match an evidential image to its source camera.
what is a latent fingerprint?
Pattern noise extracted from evidential image.
