Interviewed on BFM-TV on Thursday, October 19, Interior Minister Gérald Darmanin pointed to a convenient target to explain why the terrorist who murdered French teacher Dominique Bernard in Arras on Friday, October 13, was able to act even though he was under close surveillance by intelligence services: messaging applications.
"Until recently, traditional phone tapping gave us information about serious crime and terrorism. Today, people use Telegram, WhatsApp, Signal, Facebook, etc. (...) These are encrypted messaging systems (...) We need to be able to negotiate what you call a 'back door' with these companies. We need to be able to say, 'Mr. Whatsapp, Mr. Telegram, I suspect that Mr. X may be about to do something, give me his conversations.'"
The argument seems to be based on common sense, and Darmanin has said he is in favor of changing the law to require platforms to provide the content of encrypted messages when requested by the authorities. The problem, however, is that these requests run counter to laws that are far more difficult to change than those of the France: the laws of mathematics.
The "end-to-end" encryption used by applications such as Signal and WhatsApp works on a simple principle: it makes messages readable only by the sender and the recipient. When you send a photo, a link or a few words to a friend on Signal, for example, only the recipient has the "key" to open the virtual padlock which makes the message unreadable. Not even the messaging app administrator knows the key.
If a message is intercepted in transit from one phone or computer to another, it will only be possible to see a sequence of incomprehensible numbers and letters that are virtually impossible to decipher, given the robustness of today's algorithms. What's more, these applications do not keep copies of transmitted messages. It is therefore impossible to ask "Mr. Whatsapp" or "Mr. Telegram" to provide messages after the fact.
As things stand, the only effective way for investigators to read the content of WhatsApp or Signal conversations is simply to gain access to the phones or computers used by one or more participants in a conversation. In fact, Darmanin pointed out that this is what the agents monitoring the perpetrator of the Arras attack had tried to do, by stopping him the day before the attack in the hope of getting their hands on his cell phone, without success.
The process is random, which is why Darmanin – like a long list of politicians around the world before him – is calling for the creation of a "back door." In practical terms, this means requiring companies that manage messaging applications to provide the authorities with a "secret key" that can decrypt any message, or intentionally slip a loophole into the encryption algorithm to then give government services access.
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