Format-preserving encryption for DateTime
Zheli Liu, Chunfu Jia, Jingwei Li, Xiaochun Cheng · 2010
In many applications, such as encryption of DateTime field in database, it is desirable to encrypt items from an arbitrarily sized set with the specified format described as “YYYY-MM-DD HH:MM:SS” onto that same set. Unfortunately, conventional block ciphers such as DES, 3DES or AES are unsuitable for this purpose. The solution to it belongs to the format-preserving encryption (FPE) category. In the paper, we present an FPE scheme for DateTime based on “rank-then-cipher” mode, and then analyze its security and efficiency. We further propose a new more efficient approach named “reference-based offset encryption” to resolve the FPE problem on DateTime domain, which can be applied in message space comprised of fixed-length strings taken over some alphabet as well.