mischard

TeXyC

ASIS CTF

Task: recover a flag hashed by a custom LFSR-based algorithm embedded in a pdfTeX document. Solution: extract the TeX source and hash values from the PDF, reverse-engineer the LFSR hash with shifted hex encoding (MOP/MEP), then brute-force each 4-character chunk in parallel.

$ ls tags/ techniques/
brute_forcereverse_engineeringpdftexlatexcrclfsrhashpdfTeXmultiprocessing
PDF content extraction with pdftotextTeX source code reverse engineeringLFSR-based hash algorithm analysisParallel brute-force with multiprocessing
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