International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Paper: On the CCA Compatibility of Public-Key Infrastructure

Authors:
Dakshita Khurana
Brent Waters
Download:
Search ePrint
Search Google
Abstract: In this work, we put forth the notion of compatibility of any key generation or setup algorithm. We focus on the specific case of encryption, and say that a key generation algorithm KeyGen is X-compatible (for X \in {CPA, CCA1, CCA2}) if there exist encryption and decryption algorithms that together with KeyGen, result in an X-secure public-key encryption scheme. We study the following question: Is every CPA-compatible key generation algorithm also CCA-compatible? We obtain the following answers: - Every sub-exponentially CPA-compatible KeyGen algorithm is CCA1-compatible, assuming the existence of hinting PRGs and sub-exponentially secure keyless collision resistant hash functions. - Every sub-exponentially CPA-compatible KeyGen algorithm is also CCA2-compatible, assuming the existence of non-interactive CCA2 secure commitments, in addition to sub-exponential security of the assumptions listed in the previous bullet. Here, sub-exponentially CPA-compatible KeyGen refers to any key generation algorithm for which there exist encryption and decryption algorithms that result in a CPA-secure public-key encryption scheme {\em against sub-exponential adversaries}. This gives a way to perform CCA secure encryption given any public key infrastructure that has been established with only (sub-exponential) CPA security in mind. The resulting CCA encryption makes black-box use of the CPA scheme and all other underlying primitives.
Video from PKC 2021
BibTeX
@article{pkc-2021-30966,
  title={On the CCA Compatibility of Public-Key Infrastructure},
  booktitle={Public-Key Cryptography - PKC 2021},
  publisher={Springer},
  author={Dakshita Khurana and Brent Waters},
  year=2021
}