This final chapter gathers systems that function structurally as codes — fixed symbol sets standing in for language or binary information — even where hiding a message from a reader was never really the point. Divination, ritual literacy and priestly restriction produced their own kinds of symbolic encoding, and one system here turns out to have anticipated modern binary computing by roughly three thousand years.
The I Ching (易經, "Book of Changes") builds its entire divinatory system from a genuinely binary structure. Each of its 64 hexagrams is a stack of six lines, and each line is one of exactly two states — an unbroken line (yang) or a broken line (yin). Six positions, two possible states each, gives 2⁶ = 64 combinations: a complete six-bit binary code, arrived at independently in ancient China centuries before anyone in the West formalised binary arithmetic. The 64 hexagrams are themselves built from combining pairs of eight three-line trigrams (八卦, bagua), the same eight-fold division that underlies the Bagua map used in Feng Shui.
The Leibniz connection — in the late 1600s, German mathematician Gottfried Wilhelm Leibniz — independent co-inventor of calculus and an early theorist of binary arithmetic — was shown a hexagram diagram (the Fuxi/King Wen arrangement) by the Jesuit missionary Joachim Bouvet. Leibniz recognised that the hexagram sequence, read as broken/unbroken lines, mapped directly onto binary counting from 0 to 63. He took this as striking confirmation of his own binary system rather than its origin — but the correspondence is a genuine and well-documented point where ancient Chinese divination and the mathematical foundation of modern computing intersect.
Ogham is a genuine writing system, not fundamentally a cipher — it was used across Ireland and parts of Britain roughly from the 4th to 10th centuries CE, most visibly carved into standing stones marking territory, graves and boundaries. Its 20 (later extended to 25) characters are built from groups of parallel strokes set against a central stemline, organised into groups of five called aicmí. Most surviving Ogham stone inscriptions record straightforward personal and tribal names — genealogical markers, not secret messages.
The Germanic and Norse runic alphabets (the Elder and Younger Futhark) carried their own documented cipher traditions. Isruna ("ice-runes") replace each rune's usual carved shape with a tally-style notation: short strokes indicating which of the futhark's three groups (ættir) a rune belongs to, and how many positions into that group it falls — structurally similar in spirit to Pigpen's grid-position logic, though built from a completely independent tradition. A closely related family, sometimes called branch runes or twig runes (kvistrunar), uses the same positional-counting principle with slightly different notation.
The clearest surviving physical example combining several of these systems in one place is the 9th-century Rök runestone in Sweden, whose inscription mixes standard runes with cipher runes and other encoding techniques within a single text — a genuine ancient monument that runologists continue to actively debate the full translation of today.
In the Ptolemaic period (from 332 BCE onward), Egyptian temple scribes developed deliberately obscure hieroglyphic writing reserved for priestly and temple contexts — using rare sign readings, invented substitutions and what Egyptologists call "enigmatic" or "cryptographic" writing, most extensively documented in the temple inscriptions at Esna and Dendera. Unlike a single fixed cipher, the substitution logic varies from text to text and even within a single inscription, functioning less as a defeatable code and more as a demonstration of scribal erudition and a mechanism for restricting sacred content to an initiated priestly readership — a motive closer to the fraternal ciphers of Freemasonry than to military cryptography.
Vatsyayana's Kama Sutra (roughly 2nd–3rd century CE) lists Mlecchita Vikalpa — "the art of understanding writing in cipher, and the writing of words in a peculiar way" — among the 64 arts a cultured and accomplished person, particularly a woman of refined education, was expected to master, alongside music, poetry, perfumery and dozens of other genteel skills.
What we don't have — unlike every other system in this chapter, the Kama Sutra does not preserve the actual technical method behind Mlecchita Vikalpa in any detail that survives to us — it names the skill and lists it among accomplishments, without providing a reconstructable cipher table or procedure. Its real historical value here is as evidence that cipher literacy itself was a valued courtly accomplishment in classical Indian culture, not as a specific system that can be demonstrated or applied today.
The I Ching–binary connection is genuine and well-documented, but its direction is often misstated. Leibniz did not derive binary arithmetic from the I Ching — he had already developed it and recognised the correspondence afterward, via Bouvet. The two systems arose independently and were connected retrospectively, which is itself the more interesting and more accurate story.
Most Ogham was never secret. The cipher variants documented in the Auraicept na n-Éces are real, but the vast majority of surviving Ogham inscriptions are plain genealogical markers — treating all Ogham as inherently cryptic overstates how the script was actually used day to day.
Mlecchita Vikalpa is the clearest example in this entire section of a named tradition we cannot actually reconstruct. It belongs here as evidence of attitude and cultural value placed on cipher skill, not as a system readers can learn to use, unlike Atbash, Pigpen or even the partially-cracked Book of Soyga.