Feature: Hardware design
Power analysis Te easiest hardware attack to get started with is power analysis. Here we are monitoring the MCU’s power rails via a shunt resistor to detect differences in power consumption as the code executes. We just need a storage oscilloscope and triggers from the target to sync the scope and PC, and a means of interacting with the target hardware with a script language to automate our attacks; see Figure 1. A good getting started option here is a Python script sending characters via a serial port and controlling the device reset line. Ideally, the scope will also be able to download power traces to the PC for analysis.
For algorithms such as the Advanced Encryption Standard (AES) there is no known break other than a brute force attack of trying every possible key
With this setup we can start with simple
power analysis (SPA), looking for the difference in power consumption as the code executes. Typically this will be most evident as the code branches, as shown in Figure 2. If you can observe this kind of difference, we are in business. SPA can be used to
attack many commonly used crypto algorithms such as RSA, ECDSA, etc. To show a simple attack, we can take the
password code; see Figure 3. Here the code checks each character of the password as it is entered and has a pass/fail branch. To perform the attack we need to create a script that trials all possible characters
Figure 2: A simple branching test shows if you hardware is susceptible to power tracing
Figure 3: All the wrong character inputs follow a similar power profile, the correct input stands out
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