[Cryptography] Regulations of Tempest protections of buildings

[RB]

On Fri, Apr 7, 2017 at 2:57 PM, mok-kong shen <mok-kong.shen at t-online.de> wrote:
> Thank you for the valuable informations. Allow me though a question: Why do
> you
> continue to power feed the device, if you desire to disrupt communications
> with it?
> Wouldn't anyway be better to cut off its power supply?

Not really, no - FDE, time-based keys, and similar strong
cryptographic measures mean we want to make sure we get a clean copy
of running memory as well as storage.  This is analogous to the same
approach with laptops and desktops - for years, the first step has not
been to power off a computer, but to disconnect it from the network.
Even that's falling out of vogue for some of the more delicate
scenarios, but is functionally identical to dropping a phone in a
Faraday cage.

Blocking RF signals tends to increase power consumption in mobile
devices for various reasons, mostly due to increased radio time.
Hence the power feed so our time to analyze the device is not limited
by its charge at the time of collection.