When back doors backfire

Some spy agencies favour “back doors” in encryption software, but who will use them?

WITHOUT encryption, internet traffic might as well be written on postcards. So governments, bankers and retailers encipher their messages, as do terrorists and criminals.

For spy agencies, cracking methods of encryption is therefore a priority. Using computational brute force is costly and slow, because making codes is far easier than breaking them. One alternative is to force companies to help the authorities crack their customers’ encryption, the thrust of a new law just passed in China and a power that Western spy agencies also covet. Another option is to open “back doors”: flaws in software or hardware which make it possible to guess or steal the encryption keys. Such back doors can be the result of programming mistakes, built by design (with the co-operation of the encryption provider) or created through unauthorised tinkering with software—or some combination of the three.

The problem with back doors is that, though they make life easier for spooks, they also make the internet less secure for everyone else. Recent revelations involving Juniper, an American maker of networking hardware and software, vividly demonstrate how. Juniper disclosed in December that a back door, dating to 2012, let anyone with knowledge of it read traffic encrypted by its “virtual private network” software, which is used by companies and government agencies worldwide to connect different offices via the public internet. It is unclear who is responsible, but the flaw may have arisen when one intelligence agency installed a back door which was then secretly modified by another. The back door involved a faulty random-number generator in an encryption standard championed by America’s National Security Agency (NSA); other clues point to Chinese or British intelligence agencies.

Decrypting messages that involve one or more intelligence targets is clearly within a spy agency’s remit. And there are good reasons why governments should be able to snoop, in the interests of national security and within legal limits. The danger is that back doors introduced for snooping may also end up being used for nefarious ends by rogue spooks, enemy governments, or malefactors who wish to spy on the law-abiding. It is unclear who installed Juniper’s back door or used it and to what end.

Intelligence agencies argue that back doors can be kept secret and are sufficiently complex that their unauthorised use is unlikely. But an outsider may stumble across a weakness or steal details of it. America, in particular, has a lamentable record when it comes to storing secrets safely. In the summer it became known that the Office of Personnel Management, which stores the sensitive personal data of more than 20m federal employees and others, had been breached—allegedly by the Chinese. Some call that the biggest disaster in American intelligence history. It is rivalled only by the data taken by Edward Snowden, a former NSA contractor now living in Moscow. (The authorities responsible for airport security also let slip the details of master keys that can open most commercially available luggage—a form of physical back door.)

Push back against back doors

Calls for the mandatory inclusion of back doors should therefore be resisted. Their potential use by criminals weakens overall internet security, on which billions of people rely for banking and payments. Their existence also undermines confidence in technology companies and makes it hard for Western governments to criticise authoritarian regimes for interfering with the internet. And their imposition would be futile in any case: high-powered encryption software, with no back doors, is available free online to anyone who wants it.

Rather than weakening everyone’s encryption by exploiting back doors, spies should use other means. The attacks in Paris in November succeeded not because terrorists used computer wizardry, but because information about their activities was not shared. When necessary, the NSA and other agencies can usually worm their way into suspects’ computers or phones. That is harder and slower than using a universal back door—but it is safer for everyone else.

Fuente e imagen: www.economist.com