Apollo Guidance
Computer

Luminary 1A (rev 099) · LM lunar-descent program

READ THE ROPE. READ THE TELEMETRY. DO THE ARITHMETIC THE COMPUTER DID.

Flag Verification

Confirm a recovered flag · CTF{...}

AWAITING FLAG…

DSKY — Display & Keyboard
the crew’s interface to the Apollo Guidance Computer

1DSKY Uplink CaptureEasydecoding · two-step
Mission Brief
APOLLO GUIDANCE COMPUTER -- UPLINK CAPTURE ========================================== During the mission, Mission Control could key the DSKY remotely by sending keystrokes up on the digital uplink. Every keystroke went up three times inside one 16-bit word for integrity: the 5-bit key code, its bitwise complement, and the key code again -- so every captured word must read key, ~key, key. The key codes are the ones the computer sees on input channel 015. We captured one uplink session (uplink_capture.txt / .bin). STEP 1 Decode the capture back into the DSKY keystroke sequence the ground actually sent (Verb/Noun/numbers/Enter). STEP 2 Re-enter that exact sequence into the uplink verifier to make the computer read back what was loaded. That read-back is your flag. Verifier: submit your recovered keystroke sequence (Verbs, Nouns, digits and Enters) on the uplink verifier page.
Transmit: uplink_capture.txt · uplink_capture.bin · step-2 verifier →
2Descent Memory DumpMediumfixed-point · simulator
Mission Brief
APOLLO GUIDANCE COMPUTER -- DESCENT MEMORY DUMP =============================================== This is a dump of erasable bank E5 taken during powered descent. Buried in it is the guidance computer's current fix of the landing site: latitude, longitude, and altitude. Each quantity is an AGC double-precision value: two consecutive 15-bit ones'-complement words forming a fraction in [-1, 1). Multiply by the documented scale factor to get the physical value. LANDLAT latitude XXX.XX DEG (fraction x 180) LANDLONG longitude XXX.XX DEG (fraction x 180) LANDALT altitude XXXX.XX KM (fraction x 1024) Find the three variables (the Luminary099 symbol table gives their addresses in bank E5), decode them, and enter latitude, longitude and altitude into the descent simulator. A correct fix unlocks the flag. Files: erasable_dump_E5.txt the memory dump
Transmit: erasable_dump_E5.txt · descent simulator →
3Tampered RopeMediumforensics · bank checksums
Mission Brief
APOLLO GUIDANCE COMPUTER -- ROPE INTEGRITY INCIDENT =================================================== During pre-flight verification, a Luminary 1A (revision 099) rope image was pulled from a bench test set. It does not match the last known good build on file, and it fails its own built-in self-check. Mission assurance suspects it was altered after manufacture -- sabotage. Each bank of AGC fixed memory ends in a 'bugger word' chosen so the bank's ones'-complement sum equals the bank number. Find the bank that fails this check, recover the words that were changed, and read what the saboteur left behind. Files: Luminary099.rope.bin the suspect rope pulled from the test set Luminary099.reference.bin the last known good rope, from the vault Diff the suspect rope against the last known good copy to find the altered words. (Prefer to rebuild the known-good reference yourself? Assemble Luminary099 with yaYUL from the Virtual AGC project, github.com/virtualagc/virtualagc -- other transcriptions may not build.)
Transmit: Luminary099.rope.bin · Luminary099.reference.bin
4Custom RoutineHardreverse engineering
Mission Brief
APOLLO GUIDANCE COMPUTER -- UNDOCUMENTED VERB ============================================ A modified Luminary 1A rope contains an extra routine wired to an unused verb. When the crew keys a word into it, the routine transforms the word and compares the result against a table baked into the rope. If every entry matches, the verb 'accepts'. The rope still passes its bank self-checks -- the routine was added cleanly. Disassemble it (yaAGC's built-in disassembler, yaLEMAP, or your own), work out the transform and the table, and recover the words that would make the verb accept. Those words, read as text, are the flag. The routine lives in fixed bank 40, just past that bank's checksum word. Watch for the cycle (CYL) register and the INDEX extracode. Files: Luminary099.patched.rope.bin the modified rope
Transmit: Luminary099.patched.rope.bin

Apollo Guidance Computer · AGC / DSKY · mission status

Apollo GuidanceComputer

Flag Verification

Mission Briefing

Objective

No brute force

On AI assistance

Confirming a flag

How to win

Hints

Conduct

Apollo Guidance
Computer