Cryptology ePrint Archive: Report 2007/177
Space-Efficient Identity Based Encryption Without Pairings
Dan Boneh and Craig Gentry and Michael Hamburg
Abstract: Identity Based Encryption (IBE) systems are often constructed
using bilinear maps (a.k.a. pairings) on elliptic curves. One
exception is an elegant system due to Cocks which builds an IBE
based on the quadratic residuosity problem modulo an RSA composite
N. The Cocks system, however, produces long ciphertexts. Since
the introduction of the Cocks system in 2001 it has been an open
problem to construct a space efficient IBE system without
pairings. In this paper we present an IBE system in which
ciphertext size is short: an encryption of an L-bit message
consists of a single element in Z_N plus L+1 additional
bits. Security, as in the Cocks system, relies on the quadratic
residuosity problem. The system is based on the theory of ternary
quadratic forms and as a result, encryption and decryption are
slower than in the Cocks system.
Category / Keywords:
Date: received 10 May 2007
Contact author: dabo at cs stanford edu
Available format(s): PDF | BibTeX Citation
Version: 20070520:125819 (All versions of this report)
Short URL: ia.cr/2007/177
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