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CRC Press eBooks

Identity-Based Encryption (3)

Seong Oun Hwang, Intae Kim, Wai‐Kong Lee

Published Feb 19, 2021• 0 citations
Publisher

Abstract

This chapter provides the details of the Waters’ Identity-Based Encryption (IBE) scheme. It provides the preliminaries including the security model and hardness assumptions for the IBE scheme. The chapter gives the dual system encryption followed by the Waters’ IBE. In 2009, Waters proposed a new methodology called dual system encryption that allows us to prove that an IBE scheme is fully (adaptively) secure based on static assumptions without random oracle. The crux of Waters’ strategy is to move to a security game where both the challenge ciphertext and secret keys are semi-functional. At this point, any keys the challenger gives out are not useful in decrypting the ciphertext.

DOI
10.1201/9781003152569-15

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Informatica•Jan 1, 2012•6 citations
This chapter provides the details of the Waters’ Identity-Based Encryption (IBE) scheme. It provides the preliminaries including the security model and hardness assumptions for the IBE scheme. The chapter gives the dual system encryption followed by the Waters’ IBE. In 2009, Waters proposed a new methodology called dual system encryption that allows us to prove that an IBE scheme is fully (adaptively) secure based on static assumptions without random oracle. The crux of Waters’ strategy is to move to a security game where both the challenge ciphertext and secret keys are semi-functional. At this point, any keys the challenger gives out are not useful in decrypting the ciphertext.
An anonymous identity based encryption (anonymous IBE) scheme requires that an adversary can not determine the identity of the recipient from a ciphertext encrypted by the corresponding public key. The anonymity was formalized in previous works [1], [13], and this can be considered under chosen plaintext attack and adaptive chosen ciphertext attack, yielding two notions of security, ID-II-CPA and ID-II-CCA, where II denotes “indistinguishability of identities.” However, how to obtain an ID-II-CCA secure anonymous IBE in the random oracle model is still a challenging problem. We firstly propose a new notion of plaintext awareness in the two identities setting, called PATI. Secondly, we prove that the IBE scheme is ID-II-CCA secure if it is PATI secure. Finally, we propose the first generic conversion for anonymous IBE from ID-II-CPA to ID-II-CCA in the random oracle model.
We propose two efficient Identity-Based threshold decryption schemes.They are proved secure against chosen ciphertext attacks under the standard decisional bilinear Diffie-Hellman assumption.The first one is constructed from(one of) the Selective ID-Based Encryption(Selective-IBE) scheme proposed by Boneh and Boyen recently,yet the second one is transformed from the Full ID-Based Encryption(Full-IBE) scheme obtained by Waters.As the based IBE schemes,the attacker in the first proposal has to choose the challenge identity before the common parameter is generated.while the attacker in the second one could choose the identity adaptively.To the best of our knowledge,previous related schemes could only be proved secure in the random oracle model.
With the purpose of taking physical attacks into account in security proofs, leakage-resilient cryptography has been initiated. Recently, many leakage-resilient cryptographic primitives have been proposed. In this paper, we put forward the first leakage-resilient wicked identity-based encryption (wicked IBE) scheme. To achieve this goal, we first present a new wicked IBE scheme in the composite order groups. The security proof of this scheme is achieved via the dual system encryption technique. In contrast with existing wicked IBE schemes, the new proposal can be proved fully secure in the standard model, even when the maximum hierarchy depth is a polynomial in the security parameter. Moreover, its security is based on some standard assumptions in the composite groups, which are independent of the hierarchy depth of the scheme. Based on this newly proposed scheme, we then put forward a fully secure leakage-resilient wicked IBE scheme in the bounded memory-leakage model. The leakage here is not only allowed on the user's secret key, but also on the master secret key. Its security is proved in the standard model by a hybrid argument in a sequence of computationally indistinguishable games. To the best of our knowledge, this is the first wicked IBE scheme in the context of leakage resilience.
Recently,Identity-based Encryption(IBE) scheme based on lattices becomes one of the focuses of cryptographic research.But the IBE scheme based on standard lattice have large key size and high ciphertext expansion rate.So based on ideal lattices,this paper presents an efficient identity-based encryption scheme with small key size and low ciphertext expansion rate.The proposed scheme uses a method that combines the NTRU digital signature and the dual encryption based on ideal lattices.It is provably secure in the random oracle model.Analysis results show that the public key and the private key of key generation center contain one ring element and four ring elements respectively.The decryption key of each user is comprised of two ring elements.The ciphertext contains only two ring elements and the ciphertext expansion rate is a small constant.The encryption and decryption require four and two multiplications in the polynomial ring.Hence,the IBE scheme is more computationally efficient than that of traditional number theory based IBE scheme.
Fuzzy identity based encryption (FIBE), proposed by Sahai and Waters, is a new kind of identity based encryption. It allows users with identity w can decrypt ciphertext for w' if and only if w is close enough to w'. Recently, Ren et al. proposed a new FIBE scheme and claimed it is fully CCA2 secure in the standard model with a tight reduction. However, in this paper we will show that their scheme is not correct. Furthermore, the key generation process of their scheme cannot resist the collusion attack, which is a basic security requirement for FIBE. At last, we propose a new fully secure FIBE scheme based on the Sahai–Waters FIBE scheme and prove its security by using the “dual system encryption” technique.