Completely erasing electronic data is actually very difficult. Most of us know that moving files to the trash on our computer doesn’t actually get rid of the data in those files; it gets rid of directory information that allows easy access to the information and marks the area of the storage device as being capable of being reused. Until that area is reused, the data are still there and easy to recover.
Even after the area is overwritten with other data, more sophisticated forensic tools can generally recover the original data. All data are stored on a computer as a series of 1s and 0s. Completely erasing data requires writing all 1s over the area, then all 0s, and then repeating this multiple times. Even then if someone wants the data badly enough, there are ways of recovering it. If someone really want to get rid of the data, they must physically shred the storage medium, the actual device — or multiple devices — that stores the data within a laptop, iPad, or, in this case, a cellphone. Most of these systems store the data on multiple devices.
Not knowing what kind of text system the Secret Service uses means that it is difficult to know exactly how to recover the lost information. But there are only a couple of options, and none of them make finding the data impossible. If the texting system resides entirely on the phones themselves, then the storage on the phone would probably hold enough of a remnant of the texts that recovery would be possible. Maybe the Secret Service can’t find the information, but the FBI (or any number of private companies) surely could.
If the texting system was not only on the phones (a more usual way of doing things), then there were intermediate server computers involved. If those servers were run by the Secret Service, then copies of the messages should be recoverable from the storage on those servers. The only question is how difficult it is to find the information, and how much it would cost to recover it.
Similarly, if the Secret Service uses a secure commercial texting system such as Signal, copies of the texts would exist on the servers of the commercial firm. The messages might be encrypted, but the Secret Service should have the keys to decrypt the messages. Commercial services generally keep multiple copies of messages, along with off-line backups, making it even more likely that the messages can be recovered.
Of course, if the storage media (whether on the phones, on Secret Service servers, or on the commercial services) have been physically destroyed, it might in fact be difficult to recover the messages. Physically destroying the storage media is not a part of any sort of technology update that I’ve ever encountered and one would wonder why a standard cleanup would result in this. But again, perhaps the security of the Secret Service communication requires different kinds of upgrades. If so, the public should expect some of those details as part of the explanation for why the texts can’t be found.
Barring such an explanation, the claim that the messages were lost because of an upgrade is technologically doubtful. Recovery may not be easy, and it may cost some money, but this is the kind of thing law enforcement does all the time. If the claims of the Secret Service are to be believed, they need to provide a better, or at least more complete, story.
Jim Waldo is a professor of computer science in the school of engineering at Harvard University, teaches technology policy at the Kennedy School of Government, and is chief technology officer for the School of Engineering and Applied Sciences.