Authentication Protocols & DRYAD-Style Codebooks

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This article references parts of the story in my fiction books, The Meadow Protocol and book 2, After The Brush, part of The Continuity Chronicles series. Available in my store for signed paperback and hard copies for from Amazon to include Kindle and Audible. Understanding DRYAD-Style 4-Character Authentication: How Cipher Sheets Are Created and Used The DRYAD system (formally the DRYAD Numeral Cipher or KTC 1400 D) is a classic, paper-based challenge-response authentication method developed for military tactical communications. In environments where electronic encryption devices are unavailable, compromised, or too risky (EMP, CME, cyber-denied, or grid-down scenarios), DRYAD provides a completely analog, low-tech way to verify identity without any digital footprint beyond the spoken exchange. DRYAD sheets have uneven column lengths totaling 25 letters (A–Y) per row. A common distribution is 4,3,3,2,2,3,2,2,2,2 (for columns 0–9), summing to 25. This adjusts column 5 to 3 letters (instead of 4) to fit exactly—no empties needed. Sample DRYAD-Style Authentication Sheet VALID: 15 JAN 2026 0000Z – 16 JAN 2026 0000Z SHEET ID: SAMPLE-4CHAR-DAY15 CLASSIFIED – DESTROY AFTER USE Cryptoperiod: 24 hours (Zulu). Do not reuse any challenge-response pair within this period. Row0123456789APFSYNKRLOQBMVGJCXTHIADUEJBJYHDVCQRTLPOBUMGEKNFAISPECASFIHUQVONPEYDKBXLTJRCMNSDMLNJTOBAPDXKEYQSHFCUIVGWLEJHANFBRVUQXTLDCIEMPYKSGEJFYHJLSVGTQBKAPXIORCNFUEDCTGXMBHVGELSCRPUKNJDYQIAOFHNHOGAYFEXVSKQIMTNPRUBHJLDEIITHCGKVENIYAFBRPDSOLUMJXOKJEMAVFNGORUJLTSDPIQXKBCHTGKMAECSITHJKQPFYGRDOUXLNVBTLFETLJIKXSNUMPGQHYVBDROCSEMKDCMUQTHOYFAILVBSGEPRXNBSNAERQSNUYILOKGPJBVMHXTCFAWOHFNGQRLYSDIMBPXTAKOJUVERPPPYVGKHSMNILBECXDUQTJROFPNQYDJROXLGHSEKTMFAUNCBIPQWERKGVHIOCPJDTAMFQXUEYSLBRJNSOPTECJSQDRVGBLMUIXKYANFXBTJDPUEHRBYFNOXQTLSIKMGVAQMUOBFSUHCRJIYPVAEGMQXKLNTKTVPFBOAHUESLRGXCITMNYQJDVWGWSGILPAWTKYNBJMRFCUXVOQDDLXDQPYVJAFEBCLMHIGROKUTSNNJYIEFXJQKYSDMVURLGNCTPHBAAR Challenge Format Transmit a two-part challenge: Row letter + Column...