Method and apparatus for protecting numbers and strings using format-preserving encryption with automatic precision

Abstract

Techniques for Precision-Preserving Format-Preserving Encryption (PPFPE) to protect numeric values and strings with leading/trailing and special characters, while preserving their precision, both as a protected value (e.g., ciphertext) and when decrypted are provided. In one aspect, a plaintext string is parsed to detect a first and last sentinel characters, wherein any character(s) preceding the first sentinel character comprises a leading character(s) and any character(s) following the last sentinel character comprises a trailing character(s). Any leading character(s) preceding the first sentinel character and/or any trailing character(s) following the last sentinel character are passed through. A ciphertext string is generated by encrypting the first and last sentinel character using one or more subsets of a set of encryption characters; and encrypting the portion of the plaintext string between the first and last sentinel character using the set of encryption characters.