Outsourced decentralized multi-authority attribute based signature and its application in IoT

IoT devices often collect data and store the data in the cloud for sharing and further processing. A natural solution for secure access is directly using the device owner?s identity as the private key to generate a signature for data authentication. However this will simultaneously expose this identity. Attribute based signature (ABS), which takes the signer?s attributes instead of his/her identity as the private key, can realize data authentication while preserving the signer?s identity privacy. In ABS, there are multiple authorities that issue different private keys for signers based on their various attributes, and a central authority is usually established to manage all these attribute authorities. However, one security concern is that if the central authority is compromised, the whole system will be broken. In this paper, we present an outsourced decentralized multi-authority attribute based signature (ODMA-ABS) scheme. The proposed ODMAABS achieves attribute privacy and stronger authority-corruption resistance than existing multi-authority attribute based signature schemes. In addition, the overhead to generate a signature is further reduced by outsourcing expensive computation to a signing cloud server. We provide extensive security analysis and experimental simulation of the proposed scheme. We also propose an access control scheme that is based on ODMA-ABS

Anonymous Single-Sign-On for n designated services with traceability

Anonymous Single-Sign-On authentication schemes have been proposed to allow users to access a service protected by a verifier without revealing their identity which has become more important due to the introduction of strong privacy regulations. In this paper we describe a new approach whereby anonymous authentication to different verifiers is achieved via authorisation tags and pseudonyms. The particular innovation of our scheme is authentication can only occur between a user and its designated verifier for a service, and the verification cannot be performed by any other verifier. The benefit of this authentication approach is that it prevents information leakage of a user's service access information, even if the verifiers for these services collude which each other. Our scheme also supports a trusted third party who is authorised to de-anonymise the user and reveal her whole services access information if required. Furthermore, our scheme is lightweight because it does not rely on attribute or policy-based signature schemes to enable access to multiple services. The scheme's security model is given together with a security proof, an implementation and a performance evaluation.Comment: 3

Attribute-Based Versions of Schnorr and ElGamal

We design in this paper the first attribute-based cryptosystems that work in the classical Discrete Logarithm, pairing-free, setting. The attribute-based signature scheme can be seen as an extension of Schnorr signatures, with adaptive security relying on the Discrete Logarithm Assumption, in the random oracle model. The attribute-based encryption schemes can be seen as extensions of ElGamal cryptosystem, with adaptive security relying on the Decisional Diffie-Hellman Assumption, in the standard model. The proposed schemes are secure only in a bounded model: the systems admit $L$ secret keys, at most, for a bound $L$ that must be fixed in the setup of the systems. The efficiency of the cryptosystems, later, depends on this bound $L$. Although this is an important drawback that can limit the applicability of the proposed schemes in some real-life applications, it turns out that the bounded security of our key-policy attribute-based encryption scheme (in particular, with $L=1$) is enough to implement the generic transformation of Parno, Raykova and Vaikuntanathan at TCC\u272012. As a direct result, we obtain a protocol for the verifiable delegation of computation of boolean functions, which does not employ pairings or lattices, and whose adaptive security relies on the Decisional Diffie-Hellman Assumption

Enhanced Security of Attribute-Based Signatures

Despite the recent advances in attribute-based signatures (ABS), no schemes have yet been considered under a strong privacy definition. We enhance the security of ABS by presenting a strengthened simulation-based privacy definition and the first attribute-based signature functionality in the framework of universal composability (UC). Additionally, we show that the UC definition is equivalent to our strengthened experiment-based security definitions. To achieve this we rely on a general unforgeability and a simulation-based privacy definition that is stronger than standard indistinguishability-based privacy. Further, we show that two extant concrete ABS constructions satisfy this simulation-based privacy definition and are therefore UC secure. The two concrete constructions are the schemes by Sakai et al. (PKC\u2716) and by Maji et al. (CT-RSA\u2711). Additionally, we identify the common feature that allows these schemes to meet our privacy definition, giving us further insights into the security requirements of ABS

Certificateless Public Key Signature Schemes from Standard Algorithms

Certificateless public key cryptography (CL-PKC) is designed to have succinct public key management without using certificates at the same time avoid the key-escrow attribute in the identity-based cryptography. However, it appears difficult to construct CL-PKC schemes from standard algorithms. Security mechanisms employing self-certified key (also known as implicit certificate) can achieve same goals. But there still lacks rigorous security definitions for implicit-certificate-based mechanisms and such type of schemes were not analyzed formally and often found vulnerable to attacks later. In this work, we first unify the security notions of these two types of mechanisms within an extended CL-PKC formulation. We then present a general key-pair generation algorithm for CL-PKC schemes and use it with the key prefixing technique to construct certificateless public key signature (CL-PKS) schemes from standard algorithms. The security of the schemes is analyzed within the new model, and it shows that the applied technique helps defeat known-attacks against existing constructions. The resulting schemes could be quickly deployed based on the existing standard algorithm implementations. They are particularly useful in the Internet of Things (IoT) to provide security services such as entity authentication, data integrity and non-repudiation because of their low computation cost, bandwidth consumption and storage requirement

Versatile ABS: Usage Limited, Revocable, Threshold Traceable, Authority Hiding, Decentralized Attribute Based Signatures

In this work, we revisit multi-authority attribute based signatures (MA-ABS), and elaborate on the limitations of the current MA-ABS schemes to provide a hard to achieve (yet very useful) combination of features, i.e., decentralization, periodic usage limitation, dynamic revocation of users and attributes, reliable threshold traceability, and authority hiding. In contrast to previous work, we disallow even the authorities to de-anonymize an ABS, and only allow joint tracing by threshold-many tracing authorities. Moreover, in our solution, the authorities cannot sign on behalf of users. In this context, first we define a useful and practical attribute based signature scheme (versatile ABS or VABS) along with the necessary operations and security games to accomplish our targeted functionalities. Second, we provide the first VABS scheme in a modular design such that any application can utilize a subset of the features endowed by our VABS, while omitting the computation and communication overhead of the features that are not needed. Third, we prove the security of our VABS scheme based on standard assumptions, i.e., Strong RSA, DDH, and SDDHI, in the random oracle model. Fourth, we implement our signature generation and verification algorithms, and show that they are practical (for a VABS with 20 attributes, Sign and Verify times are below 1.2 seconds, and the generated signature size is below 0.5 MB)

Privacy-Preserving Electronic Ticket Scheme with Attribute-based Credentials

Electronic tickets (e-tickets) are electronic versions of paper tickets, which enable users to access intended services and improve services' efficiency. However, privacy may be a concern of e-ticket users. In this paper, a privacy-preserving electronic ticket scheme with attribute-based credentials is proposed to protect users' privacy and facilitate ticketing based on a user's attributes. Our proposed scheme makes the following contributions: (1) users can buy different tickets from ticket sellers without releasing their exact attributes; (2) two tickets of the same user cannot be linked; (3) a ticket cannot be transferred to another user; (4) a ticket cannot be double spent; (5) the security of the proposed scheme is formally proven and reduced to well known (q-strong Diffie-Hellman) complexity assumption; (6) the scheme has been implemented and its performance empirically evaluated. To the best of our knowledge, our privacy-preserving attribute-based e-ticket scheme is the first one providing these five features. Application areas of our scheme include event or transport tickets where users must convince ticket sellers that their attributes (e.g. age, profession, location) satisfy the ticket price policies to buy discounted tickets. More generally, our scheme can be used in any system where access to services is only dependent on a user's attributes (or entitlements) but not their identities.Comment: 18pages, 6 figures, 2 table

Attribute-Based Signcryption : Signer Privacy, Strong Unforgeability and IND-CCA2 Security in Adaptive-Predicates Attack

An Attribute-Based Signcryption (ABSC) is a natural extension of Attribute-Based Encryption (ABE) and Attribute-Based Signature (ABS), where we have the message confidentiality and authenticity together. Since the signer privacy is captured in security of ABS, it is quite natural to expect that the signer privacy will also be preserved in ABSC. In this paper, first we propose an ABSC scheme which is \textit{weak existential unforgeable, IND-CCA2} secure in \textit{adaptive-predicates} attack and achieves \textit{signer privacy}. Secondly, by applying strongly unforgeable one-time signature (OTS), the above scheme is lifted to an ABSC scheme to attain \textit{strong existential unforgeability} in \textit{adaptive-predicates} model. Both the ABSC schemes are constructed on common setup, i.e the public parameters and key are same for both the encryption and signature modules. Our first construction is in the flavor of $\mathcal{C}{t}\mathcal{E}\&\mathcal{S}$ paradigm, except one extra component that will be computed using both signature components and ciphertext components. The second proposed construction follows a new paradigm (extension of $\mathcal{C}{t}\mathcal{E}\&\mathcal{S}$), we call it ``Commit then Encrypt and Sign then Sign ($\mathcal{C}{t}\mathcal{E}\&\mathcal{S}{t}\mathcal{S}$). The last signature is done using a strong OTS scheme. Since the non-repudiation is achieved by $\mathcal{C}{t}\mathcal{E}\&\mathcal{S}$ paradigm, our systems also achieve the same

A Constant Time, Single Round Attribute-Based Authenticated Key Exchange in Random Oracle Model

In this paper, we present a single round two-party {\em attribute-based authenticated key exchange} (ABAKE) protocol in the framework of ciphertext-policy attribute-based systems. Since pairing is a costly operation and the composite order groups must be very large to ensure security, we focus on pairing free protocols in prime order groups. The proposed protocol is pairing free, working in prime order group and having tight reduction to Strong Diffie Hellman (SDH) problem under the attribute-based Canetti Krawzyck (CK) model which is a natural extension of the CK model (which is for the PKI-based authenticated key exchange) for the attribute-based setting. The security proof is given in the random oracle model. Our ABAKE protocol does not depend on any underlying attribute-based encryption or signature schemes unlike the previous solutions for ABAKE. Ours is the \textit{first} scheme that removes this restriction. Thus, the first major advantage is that smaller key sizes are sufficient to achieve comparable security. Another notable feature of our construction is that it involves only constant number of exponentiations per party unlike the state-of-the-art ABAKE protocols where the number of exponentiations performed by each party depends on the size of the linear secret sharing matrix. We achieve this by doing appropriate precomputation of the secret share generation. Ours is the \textit{first} construction that achieves this property. Our scheme has several other advantages. The major one being the capability to handle active adversaries. Most of the previous ABAKE protocols can offer security only under passive adversaries. Our protocol recognizes the corruption by an active adversary and aborts the process. In addition to this property, our scheme satisfies other security properties that are not covered by CK model such as forward secrecy, key compromise impersonation attacks and ephemeral key compromise impersonation attacks