Trifid Cipher
The Trifid cipher is a code that hides messages using a 3-layer cube of letters.
Each letter is turned into a set of three numbers based on where it sits in the cube (which layer, row, and column). Then those numbers get mixed together before being turned back into letters.
Because the letters get mixed in groups, each encrypted letter depends on several letters from the original message — which makes it harder to solve than simple substitution ciphers.
Cube string (row-first)