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Encryption backdoors for cops are unworkable, will put internet security at risk, warn experts

Demands for access to encrypted communications raise huge technical and ethical questions, according to security researchers.

Demands by police and intelligence services for secret backdoors into the encrypted communications of internet users would have a disastrous effect on the web, security experts have warned.

Law enforcement chiefs have been warning that the trend towards using strong encryption is making it much harder for them to disrupt criminal plots or investigate crimes because they cannot eavesdrop on online conversations anymore. Only this week the director of the FBI James Comey warned: "There is simply no doubt that bad people can communicate with impunity in a world of universal strong encryption."

Politicians and police chiefs on both sides of the Atlantic have been calling for some capability to be able to read emails, texts, and other messages, even if they have been encrypted. But now a group of security experts have warned that such plans would risk undermining the security of the internet itself.

The group of more than a dozen security experts including professor of security engineering at the University of Cambridge Ross Anderson, cryptographer Whitfield Diffie, and Ronald L Rivest - the 'R' in the RSA public-key cryptosystem - have put together a report looking at some of the issues involved.

"These proposals are unworkable in practice, raise enormous legal and ethical questions, and would undo progress on security at a time when internet vulnerabilities are causing extreme economic harm," they warn.

The group said there are three main problems with giving law enforcement backdoor access to strong encryption systems.

First, it would force a U-turn from security best practices such as the use of forward secrecy, whereby decryption keys are deleted immediately after use. This means stealing the encryption key used by a communications server would not compromise other messages.

Giving law enforcement special access would also "substantially increase system complexity," they said. To create the sort of system envisaged by police, the group argues, would mean that new technology features would have to be deployed and tested with hundreds of thousands of developers all around the world.

"This is a far more complex environment than the electronic surveillance now deployed in telecommunications and internet access services, which tend to use similar technologies and are more likely to have the resources to manage vulnerabilities that may arise from new features," they said.

And possibly even worse, giving law enforcement a 'backdoor' or 'magic key' to the encryption systems would create a juicy target for hackers.

"Security credentials that unlock the data would have to be retained by the platform provider, law enforcement agencies, or some other trusted third party. If law enforcement's keys guaranteed access to everything, an attacker who gained access to these keys would enjoy the same privilege," they note, adding: "Recent attacks on the United States Government Office of Personnel Management (OPM) show how much harm can arise when many organizations rely on a single institution that itself has security vulnerabilities."

It's not the first time privacy campaigners and law enforcement have clashed over the use of encryption: the last time was back in the 1990s during the so-called 'Crypto Wars', which ended when the US government backed down because the use of cryptography was clearly necessary to make the internet a viable space for business.

This time the consequences could be worse, the group of security researchers says: "We have found that the damage that could be caused by law enforcement exceptional access requirements would be even greater today than it would have been 20 years ago."

The experts said they had no problem with the idea of the need for lawful surveillance orders when they meet the requirements of human rights and the rule of law, but added: "Our strong recommendation is that anyone proposing regulations should first present concrete technical requirements, which industry, academics, and the public can analyze for technical weaknesses and for hidden costs."

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