Motivated by the lattice basis delegation technique due to [8, 22, 9], we propose a broadcast encryption scheme based on the hard worst-case lattice problems. The proposed scheme is secure in the random oracle model. To the best of the authors' knowledge, our construction constitute the first broadcast encryption schemes from lattices.
Motivated by the lattice basis delegation technique due to [8, 22, 9], we propose a broadcast encryption scheme based on the hard worst-case lattice problems. The proposed scheme is secure in the random oracle model. To the best of the authors' knowledge, our construction constitute the first broadcast encryption schemes from lattices.
Motivated by an identity-based broadcast encryption scheme from lattice(1) and a forward-secure identity-based encryption scheme(2), we propose a forward-secure identity-based broadcast encryption scheme from lattice by adding the forward-security mechanism on broadcast encryption scheme. Our scheme satisfies the security requirements of both the broadcast encrypt ion scheme and forward-security scheme, that is, it is forward-secure for the secret keys used previously, and we prove that it is semantic secure based on LWE (Learning With Error)assumption(3) in the random oracle model. In addition, our construction is believed to be secure against quantum computer.
We present a technique, which we call basis delegation, that allows one to use a short basis of a given lattice to derive a new short basis of a related lattice in a secure way. And since short bases for lattices essentially function like cryptographic trapdoors, basis delegation turns out to be a very powerful primitive. As the main application of our technique, we show how to construct hierarchical identity-based encryption (HIBE) that is secure, without random oracles, under the assumption that certain standard lattice problems are hard in the worst case. This construction and its variants constitute the first HIBE schemes from lattices, as well as the first lattice-based constructions of stateless signatures and identity-based encryption without random oracles. 1
Motivated by the need to have secure blind signatures even in the presence of quantum computers, we present two efficient blind signature schemes based on hard worst-case lattice problems. Both schemes are provably secure in the random oracle model and unconditionally blind. The first scheme is based on preimage samplable functions that were introduced at STOC 2008 by Gentry, Peikert, and Vaikuntanathan. The scheme is stateful and runs in 3 moves. The second scheme builds upon the PKC 2008 identification scheme of Lyubashevsky. It is stateless, has 4 moves, and its security is based on the hardness of worst-case problems in ideal lattices.
In this paper, a hierarchical identity-based broadcast encryption scheme is proposed based on the learning with errors problem, which is a classic hard problem on lattices. In the proposed scheme, each user's identity is associated with a lattice matrix, then the relationship between the lattice and its sub lattice could easily represent the hierarchical identity construction. Short basis of a lattice can function as a private key of a user, so based on the Sample Basis algorithm the private key of each level's user can be derived. The security proof of our proposed scheme is also given in this paper, which is IND-CCA2 secure against the attacks by outsider users and FS-CCA secure against the attacks by authorized receivers. In addition, compared with the broadcast encryption scheme based on the bilinear mapping, the scheme in this paper is more efficient in the encryption and decryption.
This paper proposes a broadcast encryption scheme over lattice which is dynamical and anonymous simultaneously. The dynamic property means that the authorized user is not fixed in proposed scheme, and the broadcaster can send the message to any receiver without any added operation. The anonymous property means that the identity of an authorized receiver is protected efficiently, any outsider attacker would not find the chosen receiver's identity. The semantic security of the proposed scheme is proven in the standard model under the hardness of the learning with errors problem (LWE).
Building cryptographic schemes upon as many fundamentally different hard problems as possible, seems to be the best way to hedge against future threats such as quantum computers. Being mainly based on the hardness of factoring and computing discrete logarithms, the present security landscape is at risk. In contrast, problems in lattices, such as finding short non-zero vectors, seem to withstand quantum computer attacks and the best known algorithms run in exponential time. In sharp contrast to other fields of cryptography, lattices admit a worst-case to average-case reduction (Ajtai 1996). Instead of assuming that a problem is hard for randomly chosen instances, lattice-based cryptosystems merely require the existence of a single hard instance, i.e., hardness in the worst case. With such an additional "trust anchor", the resulting security guarantees are much more plausible. Quite recently, we have seen an increased interest in lattice-based cryptography with many striking results. In this thesis, we are particularly interested in signature schemes, which provide a supporting pillar for today's economy. While we have seen basic signature schemes from lattices, e.g., (Gentry, Peikert, Vaikuntanathan 2008), (Lyubashevsky, Micciancio 2008), (Lyubashevsky 2009), or (Cash, Hofheinz, Kiltz, Peikert 2009), there are hardly any results dealing with the specific needs of applications, where ordinary signatures often fall too short. In this thesis, we build upon the above results and equip them with additional features, motivated by an exemplary selection of application scenarios. Hence, we demonstrate the great versatility of lattices in cryptography. In particular, we facilitate privacy-friendly electronic elections, fair online contract signing, signature compression, secure signatures in the strongest sense, as well as identity-based primitives. As far as possible, we avoid simplifying assumptions, such as the random oracle model. We believe that our techniques can be transferred to other application scenarios as well. Independently of the these results, we discuss the practical hardness of lattice problems and provide a framework for estimating the security of essentially all modern lattice-based cryptography.