Threshold Public Key Encryption Scheme Research Articles

More Constructions of Re-Splittable Threshold Public Key Encryption

The concept of threshold public key encryption (TPKE) with the special property called key re-splittability (re-splittable TPKE, for short) was introduced by Hanaoka et al. (CT-RSA 2012), and used as one of the building blocks for constructing their proxy re-encryption scheme. In a re-splittable TPKE scheme, a secret key can be split into a set of secret key shares not only once, but also multiple times, and the security of the TPKE scheme is guaranteed as long as the number of corrupted secret key shares under the same splitting is smaller than the threshold. In this paper, we show several new constructions of re-splittable TPKE scheme by extending the previous (ordinary) TPKE schemes.

Constructions of dynamic and non-dynamic threshold public-key encryption schemes with decryption consistency

Dynamic threshold public-key encryption, proposed by Delerablée and Pointcheval (CRYPTO 2008), is an extension of ordinary threshold encryption which enables decryption servers to join the system even after the setup phase, and to choose the authorized set and the threshold of decryption dynamically. Delerablée and Pointcheval proposed the first dynamic threshold public-key encryption scheme, which they proved secure under a non-standard q-type assumption. However, decryption consistency, which is an important security property that guarantees uniqueness of decryption, even when a sender and decryption servers behave maliciously, is only shown to hold in the random oracle model. In this paper, we propose three threshold public-key encryption schemes. The first and second schemes are both dynamic schemes. The former achieves a relatively weaker variant of decryption consistency, while the latter achieves a strong variant thereof. The former is a generic construction from public-key encryption with non-interactive opening (PKENO), while the latter is a specific construction from a standard number-theoretic assumption. These are the first constructions of dynamic public-key encryption, which achieve decryption consistency without relying on the random oracle model. Furthermore, both schemes can be realized based on standard assumptions. The third construction is a generic construction from PKENO achieving the strong variant of decryption consistency. This construction affirmatively answers the question indirectly posed by Galindo et al. (AFRICACRYPT 2010) of whether a generic construction achieving strong decryption consistency is possible.

Lattice-based identity-based resplittable threshold public key encryption scheme

Threshold public key encryption is a cryptographic primitive where a secret key of an organization is distributed among special members called decryption servers (insiders) and a certain threshold number of insiders must cooperate to decrypt any ciphertext. Threshold public key encryption with an additional randomized algorithm Tsplit is called resplittable threshold public key encryption (RTPKE). Cryptographic primitive RTPKE was introduced by Hanaoka et al. [Generic construction of chosen ciphertext secure proxy re-encryption, in CT-RSA, San Francisco, CA, USA, LNCS, O. Dunkelman, ed., Springer-Verlag, Heidelberg, 2012, pp. 349–364] in a generic construction of chosen ciphertext attack secure proxy re-encryption scheme. In MIST 2013 conference Singh et al. [Lattice based efficient threshold public key encryption scheme, J. Wirel. Mob. Netw. Ubiquitous Comput. Dependable Appl. (JoWUA) 4(4) (2013), pp. 93–107] presented lattice-based RTPKE scheme based on Regev's LWE [On lattices, learning with errors, random linear codes, and cryptography, in STOC, Baltimore, MD, USA, H.N. Gabow and R. Fagin, eds., ACM, University of Wales, Cardiff, 2005, pp. 84–93] assumption. In this paper, we propose lattice-based RTPKE scheme in the identity-based setting.

Threshold public key encryption scheme resilient against continual leakage without random oracles

Threshold public key encryption allows a set of servers to decrypt a ciphertext if a given threshold of authorized servers cooperate. In the setting of threshold public key encryption, we consider the question of how to correctly decrypt a ciphertext where all servers continually leak information about their secret keys to an external attacker. Dodis et al. and Akavia et al. show two concrete schemes on how to store secrets on continually leaky servers. However, their constructions are only interactive between two servers. To achieve continual leakage security among more than two servers, we give the first threshold public key encryption scheme against adaptively chosen ciphertext attack in the continual leakage model under three static assumptions. In our model, the servers update their keys individually and asynchronously, without any communication between two servers. Moreover, the update procedure is re-randomized and the randomness can leak as well.

Efficient threshold public key encryption with full security based on dual pairing vector spaces

SUMMARYMost robust and noninteractive threshold public key encryption (PKE) schemes have only been proven secure against chosen‐ciphertext attacks under the static corruption model; yet, the dynamic corruption model is more reasonable. In this paper, on the basis of bilinear groups of prime order and dual pairing vector spaces, we propose a threshold PKE scheme that is noninteractive, robust and, secure against adaptive chosen‐ciphertext attacks under the dynamic corruption model without random oracles. Moreover, our scheme is shown to be more efficient than currently existing fully secure threshold PKE schemes. Copyright © 2013 John Wiley & Sons, Ltd.

A certificateless threshold public key encryption scheme

The decryption participant’s private key share for decryption is delegated by key generation center in the threshold IBE scheme. However, a key generation center which is absolutely trustworthy does not exist. So the author presents a certificateless threshold public key encryption scheme. Collaborating with an administrator, the decryption participant generates his whole private key share for decryption in the scheme. The administrator does not know the decryption participant’s private key share for decryption. Making use of q-SDH assumption, the author constructs a certificateless threshold public key encryption scheme. The security of the scheme is eventually reduced to the solving of Decisional Bilinear Diffie-Hellman problem. Moreover, the scheme is secure under the chosen ciphertext attack in the standard model.

A Secure Decentralized Erasure Code for Distributed Networked Storage

Distributed networked storage systems provide the storage service on the Internet. We address the privacy issue of the distributed networked storage system. It is desired that data stored in the system remain private even if all storage servers in the system are compromised. The major challenge of designing these distributed networked storage systems is to provide a better privacy guarantee while maintaining the distributed structure. To achieve this goal, we introduce secure decentralized erasure code, which combines a threshold public key encryption scheme and a variant of the decentralized erasure code. Our secure distributed networked storage system constructed by the secure decentralized erasure code is decentralized, robust, private, and with low storage cost.

Identity-based Threshold Broadcast Encryption in the Standard Model

In an identity-based threshold broadcast encryption (IDTHBE) scheme, a broadcaster chooses a set of n recipients and a threshold value t, and the plaintext can be recovered only if at least t receivers cooperate. IDTHBE scheme is different from the standard threshold public key encryption schemes, where the set of receivers and the threshold value are decided from the beginning. This kind of scheme has wide applications in ad hoc networks. Previously proposed IDTHBE schemes have ciphertexts which contain at least n elements. In addition, the security of theses schemes relies on the random oracles. In this paper, we introduce two new constructions of IDTHBE for ad hoc networks. Our first scheme achieves |S|-size private keys while the modified scheme achieves constant size private keys. Both schemes achieve approximately (n-t)-size ciphertexts. Furthermore, we also show that they are provable security under the decision bilinear Diffie-Hellman Exponent (BDHE) assumption in the standard model.

Ad-Hoc Threshold Broadcast Encryption with Shorter Ciphertexts

In a threshold broadcast encryption scheme, a sender chooses (ad-hoc) a set of n receivers and a threshold t, and then encrypts a message by using the public keys of all the receivers, in such a way that the original plaintext can be recovered only if at least t receivers cooperate.This kind of scheme has many applications in mobile ad-hoc networks, characterized by their lack of infrastructure as well as for the high dynamism of their nodes. Threshold broadcast encryption schemes are much more appropriate for mobile ad-hoc scenarios than standard threshold public key encryption schemes, where the set of receivers and the threshold for decryption must be known in advance (and remain the same for the rest of the protocol).Previously proposed threshold broadcast encryption schemes have ciphertexts which contain at least n group elements. In this paper, we propose a new scheme where the ciphertexts contain essentially n−t group elements. The construction uses secret sharing techniques and the ElGamal public key cryptosystem as basic tools. We formally prove the security of the scheme, by reduction to the security of ElGamal cryptosystem.