The Rosetta Protocol Part IV: The Cartouche Cache

6 days ago
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The Rosetta Protocol Part IV: The Cartouche Cache

The decoded command from the audio pulses directed Amina to a hidden virtual machine snapshot buried deep within the British Museum’s restricted archival network. The snapshot was titled "Osiris_Node_VM.img" and had not been accessed in over a decade. She decrypted its header and confirmed that the file was locked with a dynamic encryption scheme referred to in attached metadata as a "Cartouche Seal." This is The Rosetta Protocol Part IV: The Cartouche Cache.

Digging through associated logs, Amina uncovered fragments of a forgotten research project: an experimental system designed to unlock ancient secrets using modern time-sensitive logic. The Cartouche Seal was built to change daily, its access hash generated through a unique formula. It combined two pieces of data: the time of sunrise in Cairo and the name of a Pharaoh rotated based on the day of the week.

She uncovered a handwritten table among the logs:

According to the logs, the snapshot was last successfully accessed on April 8, 2025. Amina cross-referenced that date - it was a Thursday. The Pharaoh for Tuesday was Khufu. Next, she needed to calculate the sunrise time for Cairo on that date. She used an astronomical data set to determine it was precisely 05:42.

With these two components—"HH:MM" and the name of the Pharaoh, "Khufu"—Amina constructed the input string: 05:36khufu. She hashed the string using SHA256 and obtained the hash needed to unlock the virtual machine snapshot. She held her breath and entered the hash.

CTF Challenge 4

Objective

Use a SHA256 password derived from Cairo's sunrise time and a daily rotating Pharaoh name to unlock a password-protected ZIP file. Inside is a text file containing the flag.