Julius Caesar — rotating substitutions
A rotating substitution cipher changes its key every 32 characters. The supplied artifact contains the changing-key notes and ciphertext. Recover the training flag without contacting an external service.
CASE FILE: Julius Caesar
source pattern: substitution key rotates after a fixed block
observation: each new key is recorded through the previous key
training worksheet: recover the invariant, then reason about frequency
Attribution: Adapted from Crate-CTF, 2025 challenge “Julius Caesar” by Mathias. Used under the MIT License; flags and secrets were replaced for GisVuln. See source and license details.
This GisVuln adaptation is self-contained and does not contact the original challenge infrastructure.