Cryptology ePrint Archive: Report 2015/739

Practical and Scalable Sharing of Encrypted Data in Cloud Storage with Key Aggregation

Hung Dang and Yun Long Chong and Francois Brun and Ee-Chien Chang

Abstract: We study a sensor network setting in which samples are encrypted individually using different keys and maintained on a cloud storage. For large systems, e.g. those that generate several millions of samples per day, fine-grained sharing of encrypted samples is challenging. Existing solutions, such as Attribute-Based Encryption (ABE) and Key Aggregation Cryptosystem (KAC), can be utilized to address the challenge, but only to a certain extent. They are often computationally expensive and thus unlikely to operate at scale. We propose an algorithmic enhancement and two heuristics to improve KACís key reconstruction cost, while preserving its provable security. The improvement is particularly significant for range and down-sampling queries Ė accelerating the reconstruction cost from quadratic to linear running time. Experimental study shows that for queries of size 2^15 samples, the proposed fast reconstruction techniques speed-up the original KAC by at least 90 times on range and down-sampling queries, and by eight times on general (arbitrary) queries. It also shows that at the expense of splitting the query into 16 sub-queries and correspondingly issuing that number of different aggregated keys, reconstruction time can be reduced by 19 times. As such, the proposed techniques make KAC more applicable in practical scenarios such as sensor networks or the Internet of Things.

Category / Keywords: applications/key management

Original Publication (in the same form): IHMMSec 2016

Date: received 23 Jul 2015, last revised 27 Apr 2016, withdrawn 22 Feb 2017

Contact author: hungdang at comp nus edu sg

Available format(s): (-- withdrawn --)

Version: 20170223:022412 (All versions of this report)

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