CSAIL Event Calendar: Previous Series

Space-Efficient Identity Based Encryption Without Pairings

Speaker: Dan Boneh , Stanford University
Date: October 19 2007
Time: 10:30AM to 12:00PM
Location: 32-G449
Contact: Be Blackburn, 3-6098, imbe@mit.edu
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Identity Based Encryption (IBE) systems are often constructed using 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.

We present an IBE system in which ciphertext size is short: an encryption of an s-bit message consists of a single element in Z_N plus s+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.

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