Note to future self

A DECADE ago, dozens of former fighters from both sides of Northern Ireland's Troubles sat down to talk about their roles for the oral history the Belfast Project. They were assured that the recordings would not be made public until after their deaths. But in July 2013, Boston College, which had been storing the recordings, was forced to release several tapes to Northern Ireland's police service as part of an investigation into the 1972 murder of Jean McConville.

Such transgressions have got Jonathan Zittrain, director of the Berkman Center for Internet and Society at Harvard University, thinking about how to ensure that data are protected for the promised time period. Among other concerns, he worries for philanthropic donations of papers or personal effects to libraries and the like. Often, such donations are made with a proviso that they not be revealed for a fixed period of time. “That type of donation will not happen if their stuff is only one subpoena away from disclosure,” he says.

Mr Zittrain has just received a $35,000 grant from the Knight Foundation, an organisation dedicated to "informed and engaged communities", to create an encrypted "time-capsule" service. Its aim is to enable scholars and journalists to securely send a message, in effect, into the future—encrypted in such a way that it cannot be read by anyone until a certain date or event.

There are several options for such a "dark archive". One is to lock a digital version of the message behind a cryptographic puzzle that current computers are incapable of solving, but that computers ten or 20 years in the future (presumed to be far faster and cleverer) could tackle with ease. That plan, however, is fraught with uncertainty around the pace of technological progress. There is also the chance that encrypted material might become accessible sooner than planned, for example because of the death of an interviewee.

Mr Zittrain’s idea is to use a "bank and trust" model instead. He intends to encrypt the data with the best technology available today, then split the key that unlocks the encryption into multiple fragments. Each fragment would be entrusted to a library or lawyer in a different jurisdiction, who would be instructed to hand it back only once the specified conditions had been met (or if forced to do so by some legal challenge). The key fragments could be held in physical locations such as vaults for safety, and some would be redundant, in case some disaster were to render them inaccessible.

Despite all this complexity, the system would not be designed to make it absolutely impossible to reassemble the key early, because of some imagined legal recourse. It is meant, says Mr Zittrain, "to be not as easy as a single subpoena filed on a Wednesday and you get the stuff on a Friday". He hopes to have a prototype service up and running within nine months.

Dan Wallach, a computer security expert at Rice University, in Texas, believes that Mr Zittrain has chosen the best model for his dark archive. However, he cautions that technical challenges remain, principally those around the strength of the encryption itself. The cat-and-mouse game between those who make codes and those who break them never slows, and Dr Wallach says that in order to anticipate codebreaking abilities in a distant future, "you have to over-engineer things".

Some, of course, would prefer that such time capsules not be engineered at all. In October, James Comey, director of the FBI, said that encryption "threatens to lead all of us to a very dark place", likening it to a safe that cannot be cracked. For others, such a scenario is no bad thing.

Mr Zittrain’s challenge is to build a time capsule that is flexible enough to allow early access to sensitive information as a matter of last resort, yet secure enough to protect the very disclosures that future historians will find most useful. At the moment, he fears that anyone holding information that could be of great future value, but that poses some reputational or legal risk, makes a simple choice. “They just toss it,” he says.