Three Square Cipher

The Three-Square cipher is the neglected middle child of Félix Delastelle's square-family - everyone knows the Two-Square (Double Playfair) and the Four-Square, but Three-Square is the one that encrypts digraphs using three 5×5 squares instead of two, and it never quite caught on the way its siblings did. That obscurity is precisely what makes it interesting for an ARG: it's the "nobody's heard of this one" cipher that reads as genuinely exotic, even though it's a 120-year-old paper-and-pencil scheme.

It's also a rarity in the tooling world - most online cipher suites don't even include it, which is why having it inside ComfyUI is a small flex. The pack gets it from secretpy, the only mainstream Python library that carries the full Delastelle family.

How it works

Inputs:

• text - the message.
• key_1, key_2, key_3 - three keyword strings, one per square. Three secrets, three stages to any solve.
• mode - encrypt/decrypt toggle.
• keep_formatting - on preserves formatting, off strips to lowercase letters.
• alphabet - default ENGLISH.

Output: encrypted_txt (STRING).

The mechanism is the Playfair family's: plaintext is split into letter pairs, filler x inserted where needed, and each pair is transformed by looking up positions across the three keyed squares. Because three squares are involved, the mapping is noticeably less regular than Two-Square, which is the point - harder to crack, but also easier to trip over in practice.

The inputs that matter

text plus all three keys. Every key is a secret, and every key must be non-empty. If you're designing a puzzle, the three-key structure writes the narrative for you: three keys, three clues, one message. For solving, keep_formatting on keeps spaces intact for frequency work; off gives the classic solid block.

Installing it

Part of ComfyUI ARG Toolkit - ComfyUI Manager (search "ComfyUI ARG Toolkit") or:

cd ComfyUI/custom_nodes
git clone https://github.com/AzelusLightvale/ComfyUI-ARG-Toolkit

Restart ComfyUI. Runs on secretpy; no model files.

Common issues

• Empty keys - all three need real keywords; an empty one collapses the square and mangles the output.
• Filler x - stray x characters in decrypt output are normal Playfair-family behavior, not corruption.
• External verification is hard - because Three-Square is rare in other tools, if your result looks off, sanity-check with secretpy directly in Python or a dCode.fr page rather than assuming the node is wrong; the pack's testing claims only cover common cases.