Unmodified Half-Gates is Adaptively Secure - So is Unmodified Three-Halves

Adaptive security is a crucial property for garbling schemes in pushing the communication of garbled circuits to an offline phase when the input is unknown. In this paper, we show that the popular half-gates scheme by Zahur et al. (Eurocrypt\u2715), without any modification, is adaptively secure in the non-programmable random permutation model (npRPM). Since real implementations of selective-secure half-gates are already based on npRPM, our result shows that these implementations are already adaptively secure under the same condition where selective security is proven. Additionally, we expand our analysis to cover the recent three-halves construction by Rosulek and Roy (Crypto\u2721). As a byproduct, we discuss some optimizations and separation when considering the programmable random permutation model instead