Another Technical Solution to the Encryption Debate that Involves Backdoors!

At the moment, Apple is in a legal deadlock with the FBI over access to encrypted data. But an increasing number of researchers are working on a different approach: finding a technological solution to law enforcements' demands, while protecting the privacy and security of everyday users.

One of those latest examples is "DECENT", or the "DEcryption Contract ENforcement Tool," described in a paper by Peter Linder, vice president of engineering, system solutions at infosecurity company Assured Enterprises. Linder lays out a model that, using the blockchain, hopes to provide law enforcement with decryption keys only when pre-agreed contractual requirements have been met, and create a public audit trail of the process, meaning that keys can't be demanded in secret.

"Everything done is a matter of public record," Linder told Motherboard in a phone interview. It's worth bearing in mind, however, that the paper on DECENT is fairly abstract, and doesn't deal with many of the practicalities of actually getting such a system up and running. Instead, part of the role of the paper is "to explore implementation opportunities," Linder writes.

DECENT builds on the previous idea of splitting up decryption keys and giving them to different parties. In this case, the user's device, the service provider (such as Apple), and a body known as the escrow agent would all have keys. Once two of these are combined, encrypted data can be unlocked.

Plenty of people would point to this practice as being pretty insecure: If other keys are held by various bodies rather than just the user, that creates more of an opportunity for hackers to gain access to them.

Regardless, "the service provider assumes no significant liability or risk of key theft since that key alone cannot decrypt anything," Linder writes in the paper.

"Encrypted data can be decrypted by a law enforcement agency without the owner's cooperation by using the service key […] and the escrow key," he continues.

"It is decided in advance what the contract terms are under which the decryption key should be allowed to be released," Linder told Motherboard. Perhaps those terms could reflect a lawful warrant, demanding access to data from Apple.

"When that warrant is issued, the documentation for that is delivered to the escrow agent," Linder continued. "The escrow agent looks it over and makes sure that the contract terms are satisfied, and posts the appropriate information on the blockchain." In Linder's model, it is not specified who or what the escrow agent might be, although he told Motherboard it might be a lawyer, or non-profit organisation that can determine whether a contract has been satisfied.

All of the escrow agent's activities, such as announcing that the warrant is legitimate, have to all be completed through the blockchain, Linder writes. This, he says, creates a permanent audit trail of the process.

"Everything becomes a matter of public record, everything has an audit trail, and therefore it creates a mechanism for accountability," Linder said.

Other largely abstract solutions have been proposed too. Earlier this year, cypherpunk David Chaum unveiled PrivaTegrity, a system which would rely on nine server administrators in nine different countries to decide when to decrypt communications. PrivaTegrity received a vocal backlash from parts of the information security community, in part because it seemingly had a backdoor implemented as part of its design. (Chaum disagrees with that characterisation, calling it "BS.")

MIKEY-SAKKE is another encryption solution, pushed by the UK government, that allows access to plain text data when required. The protocol gained new attention recently when one researcher published a scathing analysis of the protocol, saying that it allowed third parties to decrypt communications and contained fundamental security problems. CESG, the information security arm of the UK's GCHQ, hit back, and wrote that implementations do not contain a backdoor.

Technological solutions were also proposed in the first Crypto War in the 90s. Back in 1993, the White House announced the Clipper Chip, a piece of hardware to be placed into products which would encrypt communications, but also allow the government to listen in when required. That proposal never took off, and was shelved after a public outcry.

The criticisms of backdoors back then were very much the same as those being argued today: that any avenue of access by a third party is going to open a doorway for hackers, and generally decrease the security of users' devices.

At the moment, it looks like the standoff between law enforcement and technology companies is going to continue for some time, even with the renaissance of research into this issue.