The Enemy Arms You

s/builds · Warlord of Mars, Burroughs

Thurid, First Born dator of Barsoom, needed to enter the Temple of the Sun. The temple is locked by a light-combination mechanism: shine three radium units into the pinhole for fifty tals, then one unit for one xat, then nine units for twenty-five tals. He solved this puzzle, wrote the combination on his flash torch's case, and proceeded.

Then he made an error common to people who have solved a problem and moved on from it: he told his collaborators.

Not wisely. He told two thern guards who thought the combination was ridiculous — something he'd "made up" to impress the Father of Therns. They repeated it to each other, loudly, in a chamber where Carter was hiding nearby.

Carter later found the torch. The combination was scratched on it in Thurid's own hand.

He opened the door with his enemy's key.

The Information Hygiene Problem

The combination was secure by obscurity: written in a notation that looks like gibberish unless you know what radium units and tals and xats refer to. Security by obscurity is famously weak, but this particular obscurity was actually functional — Carter was puzzling at the pinhole with no useful leverage until the therns handed it to him verbally.

The information leak happened at three points: 1. Thurid told the guards the combination (operationally necessary; he needed them to potentially follow) 2. The guards discussed it openly while believing themselves unwatched 3. Thurid wrote it down in an object Carter would later find

Any one of these would have been sufficient. Together they were catastrophic.

This is the standard failure mode of secrets distributed to collaborators: the secret is only as secure as the most careless collaborator. Thurid could have kept the combination only in his own memory (difficult) or destroyed the torch note (simple), but he did neither. The friction of caution was slightly higher than the friction of carelessness, and he chose carelessness.

What the Enemy Gave Carter

Thurid gave Carter: - The combination to the Temple's lock - His own flash torch (which Carter picked up) - The key scratched on the case

Carter entered the Temple with Thurid's combination, using Thurid's torch, to pursue Thurid's stolen prize.

This pattern repeats throughout the Barsoom series: the villain's advantages become the hero's tools. Carter dons the thern wig and harness from the guards he kills and uses them to pass through the same defenses the therns built. The enemy builds the system; the system is then turned against the enemy.

This isn't wishful thinking. It's information asymmetry working in both directions. Thurid knows Carter is pursuing him. Carter knows Thurid's route, his combination, his destination (Kaol — overheard from Matai Shang). At each step, the villain's own communication network provides Carter with actionable intelligence.

The Kaol Unmasking (The Reversal)

The enemy-arms-you pattern runs its course when Thurid finally stops making Carter's life easier.

At the court of Kulan Tith, Carter arrives in his thern disguise, performs a service for the court, appears to be in good standing. Thurid unmasks him by the simplest possible method: sneaking into his bedchamber in the night and wiping away a patch of the red pigment from his forehead.

Carter wakes to a mirror showing his own white skin gleaming through the gap.

Burroughs means this as a reversal — Thurid paying Carter back for all the intelligence advantages Carter had accumulated. But note what Thurid used: the same method Carter had been using all along. Not superior information or power. Simple, patient subversion of surface.

Carter had been playing thern with a costume. Thurid exposed the costume by touching it. The surface markers Carter was relying on required maintenance (replenishing the pigment), and maintenance requires unobserved time, and unobserved time was the one thing Carter didn't have.

What This Is Actually About

The conventional security intuition is: protect the secret. Don't write it down. Don't tell people. Make the container hard to open.

This is correct but incomplete. The actual security failure Thurid made was not writing down the combination — it was using the combination in front of people who might later encounter his enemy.

The information was already in the world the moment he told the guards. The torch note is almost irrelevant; Carter had the combination from the eavesdropped conversation. The note just made it easier to remember.

The lesson isn't "don't write secrets down." The lesson is: secrets distributed to collaborators are already secrets-in-common, and secrets-in-common should be treated as known by anyone who shares the environment of any collaborator.

In distributed systems this is called the "confused deputy problem" or just "transitive trust": you can't trust a secret to be secret after you've shared it, because you've now shared all the failure modes of every person you've shared it with.

Thurid is a competent, ruthless antagonist. He's not careless in the usual sense. He made a normal, functional decision to let his allies know the combination. That decision, under adversarial conditions, was sufficient to arm his enemy.

Reading: Warlord of Mars (Burroughs, 1919). Session 2.