Protection of data and delegated keys in digital distribution

Masahiro Mambo, Eiji Okamoto, Kouichi Sakurai

Research output: Chapter in Book/Report/Conference proceedingConference contribution


A cryptography is quite effective in protecting digital information from unauthorized access. But if a receiver of information is determined after the encryption of the information, e.g. a posted encrypted news is withdrawn by an arbitrary user in open networks, we need an additional mechanism for converting the encrypted information into a form accessible only to an admissible user. Even though such a transformation is done by the consecutive execution of decryption of a ciphertext and re-encryption of a recovered plaintext, an intermediary plaintext may be stolen during the re-encryption. In this paper we examine secure digital distribution systems, information storage system and information provider system, in which encrypted information is directly transformed into a ciphertext of an admissible user. We show that the technique of a proxy cryptosystem is useful for establishing these distribution systems. Proposed protocols can be constructed base on the EIGamal cryptosystem or the RSA cryptosystem. Meanwhile, a blind decryption protocol provides privacy protection with respect to the selection of a ciphertext to be decrypted. In terms of digital distribution it also provides a secure information delivery. An information provider system using a blind decryption protocol possesses a problem such that a decrypting person computes exponentiation for a message freely selected by a requesting person. For such an oracle problem, a solution is known with use of a transformable signature. In this paper we show another measure prohibiting the abuse of the blind decryption protocol.

Original languageEnglish
Title of host publicationInformation Security and Privacy -2nd Australasian Conference, ACISP 1997, Proceedings
EditorsJosef Pieprzyk, Vijay Varadharajan, Yi Mu
PublisherSpringer Verlag
Number of pages12
ISBN (Print)3540632328, 9783540632320
Publication statusPublished - Jan 1 1997
Event2nd Australasian Conference on Information Security and Privacy, ACISP 1997 - Sydney, Australia
Duration: Jul 7 1997Jul 9 1997

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Other2nd Australasian Conference on Information Security and Privacy, ACISP 1997

All Science Journal Classification (ASJC) codes

  • Theoretical Computer Science
  • Computer Science(all)


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