#format-preserving-encryption 1 post tagged format-preserving-encryption. No Room for a Nonce: Disk and Length-Preserving Encryption, from XTS to FPE Jul 10, 2026 Why disk and format-preserving ciphers are deterministic, unauthenticated permutations, and how block width and domain size decide XTS, Adiantum, HCTR2, or FF1.