2010 | OriginalPaper | Chapter
Public-Key Encryption in the Bounded-Retrieval Model
Authors : Joël Alwen, Yevgeniy Dodis, Moni Naor, Gil Segev, Shabsi Walfish, Daniel Wichs
Published in: Advances in Cryptology – EUROCRYPT 2010
Publisher: Springer Berlin Heidelberg
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We construct the
first
public-key encryption scheme in the
Bounded-Retrieval Model
(BRM), providing security against various forms of adversarial “key leakage” attacks. In this model, the adversary is allowed to learn arbitrary information about the decryption key, subject only to the constraint that the overall amount of “leakage” is bounded by at most ℓ bits. The goal of the BRM is to design cryptographic schemes that can flexibly tolerate arbitrarily leakage bounds ℓ (few bits or many Gigabytes), by
only
increasing the size of secret key proportionally, but keeping
all the other parameters
— including the size of the public key, ciphertext, encryption/decryption time, and the number of secret-key bits accessed during decryption —
small and independent of
ℓ.
As our main technical tool, we introduce the concept of an
Identity-Based Hash Proof System
(
IB-HPS
), which generalizes the notion of hash proof systems of Cramer and Shoup [CS02] to the identity-based setting. We give three different constructions of this primitive based on: (1) bilinear groups, (2) lattices, and (3) quadratic residuosity. As a result of independent interest, we show that an
IB-HPS
almost immediately yields an Identity-Based Encryption (
IBE
) scheme which is secure against (small) partial leakage of the target identity’s decryption key. As our main result, we use
IB-HPS
to construct public-key encryption (and
IBE
) schemes in the Bounded-Retrieval Model.