A former UW-Madison student, convicted of jamming police radio signals during Halloween weekend in 2003, encrypted child pornography and explicit photos of his underage girlfriend so well on his computer that it took experts years to crack the code, a Dane County prosecutor said Tuesday.
Rajib K. Mitra, 32, made it nearly impossible for investigators find the pictures as they searched his computer in 2003 for evidence of his involvement in radio disruptions that crippled emergency communication, Assistant District Attorney Robert Kaiser said.
But Milwaukee Police Detective Rick McQuowen testified that he was able to break the encryption in 2009, at the invitation of a Madison detective, using some new techniques he had learned.
Mitra, who is scheduled for release from federal prison next month after serving an eight-year sentence, is charged in Dane County Circuit Court with eight counts of possessing child pornography and two counts of sexual exploitation of a child.
Madison police Detective Cynthia Murphy, a computer forensics expert, said the file names of the images could be found using forensic software, but the images themselves were encrypted in directories called "porn\bad" and "porn\me."
Mitra's lawyer, Assistant Public Defender Jon Helland, said in his opening statement that the child pornography that Mitra allegedly downloaded from the Internet came to him already encrypted with adult pornography that he had downloaded. He said that Mitra put it in the "bad" directory on his computer because he was unable to open it and see what it was.
Helland also disputed whether there is any proof that any of the people depicted in the videos or pictures are actually children and not young-looking adults.
Nude photos of Mitra's girlfriend, who was 16 at the time, could have been put on Mitra's computer by the girl, whose camera was used to take some of the pictures, Helland said.
But the girl, now 24, testified Tuesday that at the time she didn't know how to transfer pictures from the digital camera that Mitra had given her for Christmas in 2002 onto a computer. And she wasn't sure how Mitra did it either, she testified.
Testimony in Mitra's trial is expected to wrap up Wednesday.