—The primitive of forward-secure identity-based encryption was proposed in order to minimize the damage of private key exposure in identity-based encryption setting. This new primitive guarantees that even if the current private keys are compromised, it is not possible to compromise past secret keys and past communications. In this paper, we propose a generic construction of forwardsecure identity-based encryption. To do so, we first introduce a relaxed variant of hierarchical identity-based encryption called identity-based binary tree encryption and construct a concrete identity-based binary tree encryption scheme that is provably chosen-ciphertext secure in the standard model. We then show how to generically construct forward-secure identity-based encryption from identitybased binary tree encryption. Based on the proposed identity-based binary tree encryption scheme, we obtain a forward-secure identity-based encryption scheme with chosen-ciphertext security in the standard model.
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