One computer security concern is that various insiders — including hardware and software manufacturers, and governments which may compel them to comply — will build back doors into their products to allow the security to be compromised.
Doing this is a terrible idea. A back door put in for government surveillance or police use is also vulnerable to use for any purpose by anyone who discovers it. There’s no way to create strong encryption and security against everyone except the government, so building in back doors means deliberately spreading insecure systems throughout your society. When you deliberately design your systems to be vulnerable to one attacker (however well-motivated and regulated) you inevitably create an attack vector for an unauthorized person. You also face vulnerability if the mechanism of the backdoor is reverse engineered by unregulated agents, like criminal groups or foreign governments. With the degree of espionage focused in high-tech industry, it’s hard to imagine that any government could keep their back door strictly for their own use when well-resourced and determined opponents would also achieve many objectives through access.
The latest high-profile example of such a back door is the revelation that Swiss cryptography firm Crypto AG was secretly owned by the CIA. There have been numerous recent news stories, but the same information was reported in 1995. The National Security Archive has some further context.
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