[Resource Topic] 2002/060: A Forward-Secure Public-Key Encryption Scheme

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A Forward-Secure Public-Key Encryption Scheme

Authors: Jonathan Katz


Cryptographic computations are often carried out on insecure devices for which the threat of key exposure represents a serious and realistic concern.
In an effort to mitigate the damage caused by exposure of secret data stored on such devices, the paradigm of \emph{forward security} was introduced.
In this model, secret keys are updated at regular intervals throughout the lifetime of the system; furthermore, exposure of a secret key corresponding to a given interval does not enable an adversary to ``break’’ the system (in the appropriate sense) for any \emph{prior} time period.
A number of constructions of forward-secure digital signature schemes and symmetric-key schemes are known.

We present the first construction of a forward-secure public-key encryption scheme whose security is based on the bilinear Diffie-Hellman assumption in the random oracle model.
Our scheme can be extended to achieve chosen-ciphertext security at minimal additional cost.
The construction we give is quite efficient: all parameters of the scheme grow (at most) poly-logarithmically with the total number of time periods.

ePrint: https://eprint.iacr.org/2002/060

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