This is an interesting topic, here's what I came up with after a bit of googling: 1. The Nikon Authenticated Image system probably uses a hardware key. I could

This is an interesting topic, here's what I came up with after a bit of googling: 1. The Nikon Authenticated Image system probably uses a hardware key. I couldn't find info on the official nikon site, but according to this guy it does ( http://blogs.verisign.com/websecurity/2008/07/drowning_in_disinformation.php http://blogs.verisign.com/websecurity/2008/07/drowning_in_di... ) 2. According to another site, an established secure chain of custody for images with severely restricted write permissions is usually sufficient: http://www.crime-scene-investigator.net/admissibilityofdigital.html http://www.crime-scene-investigator.net/admissibilityofdigit... FWIW I know an LAPD crime scene photographer and they're shooting digital.