Ends-messaging protocol that recovers and has backward security

Details Ends-messaging protocol that recovers and has backward security Ends-messaging protocol that recovers and has backward security

2011-03-01

2011-03-01

Colin, Carl (Department: 2493)

Cryptography

Key management

C380S045000, C380S047000, C380S278000, C380S279000, C380S280000, C380S282000, C380S283000, C380S285000

Reexamination Certificate

active

07899184

ABSTRACT:
The presented messaging protocol uses three new public keys in a signed and encrypted message to achieve backward security and recovery in an environment where an attacker now and then obtains the security parameters in exposed, decrypted form. Backward security is understood to mean that an adversary cannot decrypt those captured encrypted messages that the user has decrypted prior the exposure. The recovery of the protocol means that the attacker at some point of time after the exposure cannot any more decrypt messages created after the exposure. The invention can be used e.g. in encrypted email communication. New to the current state of the art is that a message contains history data: a list of recently used public keys and their Diffie-Hellman counterparts. Also new is the usage of a stored and pseudorandomly changing data used together with a just computed Diffie-Hellman shared secret to provide a value that an attacker cannot produce if he does not have a proper exposed security data and the private key required to compute the Diffie-Hellman shared secret.

REFERENCES:
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Canetti et al. (‘A Forward-Secure Public-Key Encryption Scheme’, Inproceedings, 2003, pp. 255-271, http://eprint.iacr.org/2003/083.pdf).
Bellare et al. (‘Forward-Security in Private-Key Cryptography’, An extended abstract of this paper appears in the Proceedings of the CT-RSA 2003 conference. This is the full version. Date: May 5, 2001, last revised Nov. 18, 2002; pp. 1-24, http://eprint.iacr.org/2001/035).

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