Paper 2025/1064 Original: eprint.iacr.org/2025/1064 ↗

Achieving Blockchain-Secured Cryptographic Primitives from Signature-Based Witness Encryption

Abstract

Goyal and Goyal demonstrated that extractable witness encryption, when combined with smart-contract equipped proof-of-stake blockchains, can yield powerful cryptographic primitives such as one-time programs and pay-to-use programs. However, no standard model construction for extractable witness encryption is known, and instantiations from alternatives like indistinguishability obfuscation are highly inefficient. This paper circumvents the need for extractable witness encryption by combining signature-based witness encryption (Döttling et al.) with witness encryption for KZG commitments (Fleischhacker et al.). Inspired by Goyal et al., we introduce $T+1$-Extractable Witness Encryption for Blockchains ($T+1$-eWEB), a novel primitive that encrypts a secret, making its decryption contingent upon the subsequent block's state. Leveraging $T+1$-eWEBs, we then build a conditional one-time memory, leading to a $T+1$ one-time program ($T+1$-OTP) also conditional on the next block's state.