Two blocks of eleven (aleph–kaf, lamed–tav), and within each block the letters are mirrored: aleph↔kaf, bet↔yod, gimel↔tet, dalet↔chet, he↔zayin, vav↔vav; then lamed↔tav, mem↔shin, nun↔resh, samekh↔qof, ayin↔tsadi, pe↔pe. Two letters are their own substitutes. אמת becomes כשל (aleph→kaf, mem→shin, tav→lamed) — a word, 'stumbling', which is the kind of result the method lives on.
Achbi mirrors within each half rather than across the whole alphabet, so a word's letters stay in their own half — a gentler scrambling than atbash, which changes every letter for one at the other end. The Kabbalists use it in the same exegetical way as albam, to produce a legible second word from a first, and the self-pairing of vav and pe is a feature of the eleven-and-eleven division.
Nothing in the library points at this entry yet.