Key-insulated public key cryptosystems

Yevgeniy Dodis, Jonathan Katz, Shouhuai Xu, Moti Yung

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


Cryptographic computations (decryption, signature generation, etc.) are often performed on a relatively insecure device (e.g., a mobile device or an Internet-connected host) which cannot be trusted to maintain secrecy of the private key. We propose and investigate the notion of key-insulated security whose goal is to minimize the damage caused by secret-key exposures. In our model, the secret key(s) stored on the insecure device are refreshed at discrete time periods via interaction with a physically-secure – but computationally-limited – device which stores a “master key”. All cryptographic computations are still done on the insecure device, and the public key remains unchanged. In a (t,N)-key-insulated scheme, an adversary who compromises the insecure device and obtains secret keys for up to t periods of his choice is unable to violate the security of the cryptosystem for any of the remaining N−t periods. Furthermore, the scheme remains secure (for all time periods) against an adversary who compromises only the physically-secure device. We focus primarily on key-insulated public-key encryption. We construct a (t,N)-key-insulated encryption scheme based on any (standard) publickey encryption scheme, and give a more efficient construction based on the DDH assumption. The latter construction is then extended to achieve chosen-ciphertext security.

Original languageEnglish (US)
Title of host publicationAdvances in Cryptology - EUROCRYPT 2002 - International Conference on the Theory and Applications of Cryptographic Techniques, 2002, Proceedings
EditorsLars R. Knudsen
PublisherSpringer Verlag
Number of pages18
ISBN (Print)9783540435532
StatePublished - 2002
EventInternational Conference on the Theory and Applications of Cryptographic Techniques, EUROCRYPT 2002 - Amsterdam, Netherlands
Duration: Apr 28 2002May 2 2002

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


OtherInternational Conference on the Theory and Applications of Cryptographic Techniques, EUROCRYPT 2002

ASJC Scopus subject areas

  • Theoretical Computer Science
  • General Computer Science


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