SET-OT: A Secure Equality Testing Protocol Based on Oblivious Transfer

We propose a new secure equality testing (SET) protocol, namely SET-OT, for two-party setting by using a recently introduced Private Set Membership Protocol (PSM) based on Oblivious Transfer (OT) as a building block. We designed our equality test in such a way that the test result will not be revealed in clear text, which is desired in several cryptographic protocols. The advantage of using OT is that with the help of OT Extension (OTE) protocols, the cost of asymmetric operations per OT operations reduces when the number of OT executions increases. This makes our protocol competitive especially for the cases where the number of equality tests to be invoked is high. When the number of equality test increases, the time complexity of SET-OT converges to one asymmetric key decryption operation, this operation is the dominant part in terms of computational cost. SET-OT has a better performance in terms of the communication rounds and data transmission cost than state-of-the-art solutions: three communication rounds and 2.9 KB of data transmission are the communication costs of performing equality testing protocol for 20-bit string pairs. In addition to our complexity analysis, we also present test results to validate our claim on performance.