LibFTE is the first general-purpose library that introduces a unifying framework
for general-purpose development and deployment of FPE or FTE schemes using 
formats specified by regular expressions. LibFTE also overcomes some technical 
limitations of the prior FTE software.

Previously, ranking was performed using the Deterministic Finite Automata (DFA)
representation of regular expressions, which means that format-abiding 
encryption was feasible only for regular expressions for which the DFA 
representation could be built.

WWW: https://libfte.org/