Public-Key Encryption with Delegated Search


Ibraimi, Luan and Nikova, Svetla and Hartel, Pieter and Jonker, Willem (2011) Public-Key Encryption with Delegated Search. In: 9th International Conference on Applied Cryptography and Network Security, ACNS 2011, June 7-10, 2011, Nerja, Malaga, Spain.

Abstract:In public-key setting, Alice encrypts email with public key of Bob, so that only Bob will be able to learn contents of email. Consider scenario when computer of Alice is infected and unbeknown to Alice it also embeds malware into message. Bob's company, Carol, cannot scan his email for malicious content as it is encrypted so burden is on Bob to do scan. This is not efficient. We construct mechanism that enables Bob to provide trapdoors to Carol such that Carol, given encrypted data and malware signature, is able to check whether encrypted data contains malware signature, without decrypting it. We refer to this mechanism as Public-Key Encryption with Delegated Search SPKE.

We formalize SPKE and give construction based on ElGamal public-key encryption (PKE). proposed scheme has ciphertexts which are both searchable and decryptable. This property of scheme is crucial since entity can search entire content of message, in contrast to existing searchable public-key encryption schemes where search is done only in metadata part. We prove in standard model that scheme is ciphertext indistinguishable and trapdoor indistinguishable under Symmetric External Diffie-Hellman (sxdh) assumption. We prove also ciphertext one-wayness of scheme under modified Computational Diffie-Hellman (mcdh) assumption. We show that our PKEDS scheme can be used in different applications such as detecting encrypted malwares and forwarding encrypted emails.
Item Type:Conference or Workshop Item
Copyright:© 2011 Springer
Electrical Engineering, Mathematics and Computer Science (EEMCS)
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