Efficient Actively Secure OT Extension: 5 Years Later

Abstract: Oblivious Transfer (OT) is a fundamental cryptographic primitive that has been used as a building block in many efficient MPC protocols. Whilst OT inherently requires public-key cryptography, recent advances in the field show that in practice, OT can no longer be considered an expensive primitive. This is mainly due to the OT extension technique of Ishai, Kilian, Nissim and Petrank (CRYPTO 2003), which cheaply produces a large number of OTs starting from just a few seed OTs. In this talk, we will describe the actively secure OT extension protocol of Keller, Orsini and Scholl (CRYPTO 2015) and some variants, and discuss lessons learnt and subsequent developments from the last few years.