miscPromedium
Точечный выбор (Pointed Selection)
hackerlab
Task: a PNG of a black-dot grid (DotCode 2D barcode) whose IHDR height is falsified to hide a second symbol below the declared image. Solution: re-decode IDAT past the fake height to reveal the hidden symbol, then build a DotCode decoder by reversing zint's dotcode.c; the visible top symbol is a decoy, the hidden bottom symbol holds the real flag.
$ ls tags/ techniques/
hidden_datadecoy_flagdotcode2d_barcodepng_height_overflowidat_overreadreed_solomon_gf113zint_oracledot_grid
png_ihdr_height_falsificationidat_scanline_overreaddotcode_lattice_detectionparity_lattice_identificationdotcode_decoder_from_zintcodeset_abc_state_machine
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