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→1-C: Modified First-Round Key
==== 1-C: Modified First-Round Key ====
The first step is to perform a standard CPA attack. The only issue is Remember we won't recover the actual encryption key used <math>k</math>, instead we recover <math>k \oplus CBC_{m-1} \oplus CTR_{m}</math>, since we basically roll all the constant inputs into what we call a `modified key'.
So let's do a first-round attack focused around points (180000,22000) to start (roughly picked from the power traces). To do this: