Espressif ESP32: Breaking HW AES with Power Analysis (2023)

Re:Espressif ESP32: Breaking HW AES with Power Analysis (2023) by Retr0id on Saturday February 10, 2024 @10:54AM (#39327078)

When you look at a power trace of a whole AES operation, it's usually quite obvious when it starts and stops - you can see a pattern that repeats for each round. If you acquire a slightly larger window, you can align your traces after you've captured them (by shifting them until the average difference is small). This is quite doable but it is a whole extra step, so a trigger pin is always preferable.

The ChipWhisperer Husky has an "analog pattern" trigger mode[1], which can help with this sort of thing.

[1] https://rtfm.newae.com/Capture/ChipWhisperer-Husky/

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Re:Espressif ESP32: Breaking HW AES with Power Analysis (2023) by jacquesm on Saturday February 10, 2024 @11:00AM (#39327134)

Does that still hold if you have no idea what's running on the device? Or does that just help to narrow down the blocks of samples to test to a small enough section that you can brute force the remainder?

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Re:Espressif ESP32: Breaking HW AES with Power Analysis (2023) by Retr0id on Saturday February 10, 2024 @11:03AM (#39327175)

I'd say for it to be practical, you'd need to know the rough time window (within seconds) that the device is doing cryptography within. For example, if it's got an encrypted bootloader, you can reliably expect it to start decrypting stuff shortly after power on.

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Re:Espressif ESP32: Breaking HW AES with Power Analysis (2023) by jacquesm on Saturday February 10, 2024 @11:53AM (#39327785)

I can see how auto correlation might work on the signal traces if you have enough of them.

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