Byte-at-a-time ECB decryption (Harder)

Take your oracle function from #12. Now generate a random count of random bytes and prepend this string to every plaintext. You are now doing:

AES-128-ECB(random-prefix || attacker-controlled || target-bytes, random-key)

Same goal: decrypt the target-bytes.

Stop and think for a second.

What's harder than challenge #12 about doing this? How would you overcome that obstacle? The hint is: you're using all the tools you already have; no crazy math is required.


Cryptography Services | NCC Group