PoS Blockchain-Based Forward-Secure Public Key Encryption with Immutable Keys and Post-Compromise Security Guarantees

摘要

We present a forward-secure public-key encryption (PKE)scheme without key update, i.e. both public and private keys are immutable.In contrast, prior forward-secure PKE schemes achieve forward securityby constantly updating the secret keys. Our scheme is based on witnessencryption by Garg et al. (STOC 2013) and a proof-of-stake blockchainwith the distinguishable forking property introduced by Goyal et al. (TCC2017), and ensures a ciphertext cannot be decrypted more than once, therebyrendering a compromised secret key useless with respect to decryption ofpast ciphertext the legitimate user has already decrypted. In this work,we formalize the notion of blockchain-based forward-secure PKE, show thefeasibility of constructing a forward-securePKEscheme without key update,and discuss interesting properties of our scheme such as post-compromisesecurity.