Paper 2007/201

The BBG HIBE Has Limited Delegation

Hovav Shacham

Abstract

At Eurocrypt 2005, Boneh, Boyen, and Goh presented a hierarchical IBE for which they claimed a novel property, called limited delegation: it is possible to give an entity a private key that restricts it from generating descendant private keys beyond some depth d; in particular, with d equal to the entity's depth, such a key allows decryption only. In this paper, we argue that this claim is nonobvious and requires proof, provide a precise model for arguing about limited delegation, and prove that the Boneh-Boyen-Goh system does, in fact, have limited delegation. Whereas Boneh, Boyen, and Goh prove their system semantically secure under the BDHI assumption, our proof of limited delegation requires the stronger BDHE assumption.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
Published elsewhere. Unknown where it was published
Keywords
identity-based encryptionlimited delegationBDHE
Contact author(s)
hovav @ cs stanford edu
History
2007-05-31: received
Short URL
https://ia.cr/2007/201
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2007/201,
      author = {Hovav Shacham},
      title = {The BBG HIBE Has Limited Delegation},
      howpublished = {Cryptology ePrint Archive, Paper 2007/201},
      year = {2007},
      note = {\url{https://eprint.iacr.org/2007/201}},
      url = {https://eprint.iacr.org/2007/201}
}
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