Advertisement
Published in:
2017 | OriginalPaper | Chapter
9. Insider Privacy
Author : Laila El Aimani
Published in: Verifiable Composition of Signature and Encryption
Publisher: Springer International Publishing
Activate our intelligent search to find suitable subject content or patents.
Select sections of text to find matching patents with Artificial Intelligence. powered by
Select sections of text to find additional relevant content using AI-assisted search. powered by
Abstract
So far, privacy (invisibility/confidentiality) of the case-study primitives was considered in the outsider model. This explains the success in “amplifying” security of the “base” encryption; i.e. building from CPA secure encryption (wCCA secure encryption in the multi-user setting) CCA secure confirmer signatures or signcryption. Such an amplification cannot hold in the insider model since the adversary is given the signing key and can compute valid confirmer signatures/signcryptions on messages of his choosing and then submit them for verification/decryption. Therefore, the best and most optimistic result we can hope for is to at least preserve security and base the CCA security of our primitives on the CCA security of the underlying encryption.
In addition to the expensive cost of CCA secure encryption, another caveat consists in impeding verifiability as (partially) homomorphic encryption is no longer allowed in the design. It is therefore imperative to look for an alternative encryption that allows to efficiently prove knowledge of a decryption while enjoying CCA security. In this chapter, we investigate the methods used to upgrade security in public-key encryption, and adapt them to design insider-secure confirmer signatures and signcryptions without compromising verifiability.