Comparing Encrypted Strings

Document Type

Conference Proceeding

Publication Date



Database outsourcing, also known as database as a service, has become a popular way to store and process large amounts of data. Unfortunately, remote data storage can compromise confidentiality. An obvious solution is to encrypt data, prior to storage, but encrypted data is more difficult to query. We describe and demonstrate an efficient scheme for comparing ciphertexts, corresponding to arbitrary plaintexts, in such a way that the result is the same as if the plaintexts had been compared. This allows queries to be processed remotely and securely. Comparison is not limited to equality. For example, encrypted employee names can be sorted remotely without decryption. Any encryption algorithm can be used. Demonstration queries are shown in SQL.


Cyber Security is volume 589 of the Communications in Computer and Information Science series.