Not that such an approach is impossible: companies like Facebook, Google, Apple and so on could redesign their systems to make it possible to decrypt them. They could even avoid the problem of a simple backdoor by using constantly changing encryption keys – so long as they keep a copy of those keys.
When the authorities then turn up and ask for specific messages from specific users to be decrypted, the company in question could match the messages with the encryption key used in each case. That would certainly provide additional layers of security and make it much harder for a malicious third party to gain access to messages.
But – and it is a very big "but" – the issue is over whether the companies, and ordinary citizens, trust the security services not to abuse the system. And there is a wealth of evidence to suggest that any such trust would be misplaced.
As we know from the Snowden documents as well as efforts from politicians such as senator Ron Wyden, the authorities have repeatedly developed secret and transparently flawed legal justifications to extend their powers far beyond what the law explicitly states.
For example, the ability to collect the details of every single phone call made over Verizon and AT&T's networks was eventually achieved through the issuance of a single piece of paper, renewed in secret every three months.
And despite Congress' best efforts, the US security services are still refusing to say how many US citizens' details are held in a vast database that was created illegally through misinterpretation of the FISA Act, a piece of legislation specifically tailored to gather information only on non-citizens. Congress started asking for the figure seven years ago.
The governments on both sides of the Atlantic do of course have good and valid reasons for wanting to be able to access encrypted communications, especially given the spate of recent terrorist attacks.
But the reality is that the security services have become addicted to the easy search capabilities that come from mass surveillance, rather than the much harder task of pinpointing and targeting individuals.
And there is no evidence that they are willing to let that position go. Especially when they can work the political systems and use the terrorism threat to push through legislation that restores their ability to spy on anyone at will. ®