Identity-Based Format-Preserving Encryption

We introduce identity-based format-preserving encryption (IB-FPE) as a way to localize and limit the damage to format-preserving encryption (FPE) from key exposure. We give definitions, relations between them, generic attacks and two transforms of FPE schemes to IB-FPE schemes. As a special case, we introduce and cover identitybased tweakable blockciphers. We apply all this to analyze DFF, an FPE scheme proposed to NIST for standardization.