Cryptology ePrint Archive: Report 2007/217

Identity-Based Broadcast Encryption

Ryuichi Sakai and Jun Furukawa

Abstract: Broadcast encryption schemes enable senders to efficiently broadcast ciphertexts to a large set of receivers in a way that only non-revoked receivers can decrypt them. Identity-based encryption schemes are public key encryption schemes that can use arbitrary strings as public keys. We propose the first public key broadcast encryption scheme that can use any string as a public key of each receiver. That is, identity-based broadcast encryption scheme. Our scheme has many desirable properties. The scheme is fully collusion resistant, and the size of ciphertexts and that of private key are small constants. The size of public key is proportional to only the maximum number of receiver sets to each of which the ciphertext is sent. Note that its size remains to be so although the number of potential receivers is super-polynomial size. Besides these properties, the achieving the first practical identity-based broadcast encryption scheme itself is the most interesting point of this paper. The security of our scheme is proved in the generic bilinear group model.

Category / Keywords: public-key cryptography / broadcast encryption, ID based encryption, bilinear map, revocation

Date: received 6 Jun 2007, last revised 13 Jun 2007

Contact author: sakai at isc osakac ac jp

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Version: 20070613:063701 (All versions of this report)

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