By Robert Lynch
Alethia walked into the lab tech’s office. “You wanted to see me?”
“Yes,” Steve said, “The Baronkoff murder. I have bad news.”
“The forensics came back?” Alethia asked.
“Not on the physical evidence,” Steve said. “Computer evidence shows that the security footage has been tampered with.”
“Tampered how, and how do you know?” Alethia asked.
“I’ll answer the second first,” Steve said, “The file’s image encrypting data doesn’t match.”
“Image encrypted?” Alethia asked. “I haven’t heard of that.”
“It’s old computer tech.” Steve replied, “As image rendering software reached the ability to mimic faces and produce fake images, deep fakes they were called back then, security tech developed to implant codes into digital images.”
Steve took a still image and zoomed in until the image was heavily pixelated. Alethia couldn’t see anything.
“It just looks like pixels,” Alethia said.
“It is just pixels.” Steve said, “There are different colour schemes, but I’ll focus on what this system uses. Each pixel is made up of three numbers; how much red, green, and yellow should be in each pixel. A number between 0 and 255 represents each colour.”
“Ok,” Alethia said.
“The security encryption is based on changing the colour numbers. A complete dark image is made up when all the pixels have all colours at 255. Once the security law came in, the values were changed so that every second pixel in a photo had a max of 254.” Steve said.
“So a grid of black and slightly less black pixels,” Alethia said.
“Right,” Steve said. “Such a small change can only be seen if the pixels are huge, and the pixel density that we use today makes it impossible to see.”
“How does a grid help?” Alethia asked.
“It’s a trinary waveform,” Steve said. “By knowing what we expect to see, we can edit the colour numbers of the grid to become trinary bits. And those bits form repeated QR codes in the image which decryption programs can render.”
Steve clicked, and the image rendered into a patchwork of QR codes spread across the image.
“Essentially overnight, it made image manipulation really hard.” Steve said, “If you put two images together, then it has the encryption of two different pictures in it.”
Steve scrolled out. The pattern of QR codes was interrupted with a different sequence in the shape of a man.
“Obviously, digital data can be edited.” Steve said, “But the encryption on the trinary code is also be updated. So you can delete the embedded image and write a new one, but you need to have the exact encryption protocols for the firmware.”
“That doesn’t look to what happened here,” Alethia said.
“No,” Steve said, “This is incredibly more primitive. It’s a simple add-in. There’s lots of commercially available software that lets you do that. And editing an image for art or whatever isn’t illegal.”
“I remember that there is a statute on edit security data,” Alethia said, “but I only vaguely remember it from a criminal law class; I’d have to look it up.”
“I’ll save you the trouble,” Steve said, “I looked it up earlier; it only applies to Government security footage, not private.”
“No matter,” Alethia said. “What, if anything, can be gleaned from this security video, or is it all out?”
“Most of the data is correct. I will render a copy that cuts out the edited data and send it to you; maybe there is something in the video, but I doubt it.” Steve said, “It does give us some information on the Baronkoff murder, though. Whoever did it only knew about commercial video editing and no background in image security.”
“So that narrows it down to everyone that’s ever been a teenager,” Alethia said. “Let’s hope that forensics comes back with something.”