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Suppose a mischievous coffeeshop wifi gateway wants to drain phone batteries.

It is easy to see how it might weaken signals and flip a few bits to wreak NAK havoc at the link level so wifi chip power consumption is maximal.

But, how could it waste power on the main CPU chip?

With phone wifi speeds now exceeding 1 Gbps, I wonder if the gateway could just fabricate packets to unused ports so that the firewall needs to throw away millions of packets per second (which, I believe, never issues a warning to the user). Or, if it could fabricate packets to used ports so that phone applications get errors (which probably alerts the user, so I'd prefer a different mischief scenario). Or?

It at least seems plausible that a mischievous gateway could prevent the main CPU from entering any low-power standby mode. So, if the user is just drinking coffee and watching people walk by (waiting two hours for a Whatsapp message with the phone screen off), how much more power would a mischievous gateway generate, compared to a normal gateway, on a typical modern phone? 2x? 10x?

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  • One of my devices didn't support hardware checksum offloading on OpenBSD, and as a result it ended up using a good chunk of the CPU when I was sending lots of traffic to it (vs 0% on Linux). It's not inconceivable that wireless network packets could increase CPU usage on some phone hardware/software. – user Oct 6 '20 at 14:25

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