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There are many constraints in the use of digital signatures. This paper proposes a new way of using digital signatures with some restrictions, i.e. set signatures. It works in such a way that when the signing algorithm is given, one can use it to create a valid signature on a message if and only if the message belongs to a pre-defined set, and given the information about the signing algorithm, it is computationally infeasible to create valid signatures on any other arbitrary messages outside of the set. This special property enables the signing algorithm to be made public, which seems to contradict with the traditional signature where a private key is needed, which must be kept secret. What makes the problem challenging is that the signing algorithm does not reveal the secret signing key, and hence forging normal signatures for arbitrary messages is computationally infeasible. In many cases, the signing algorithm does not reveal the elements in the authorized set. As an application of the new concept, set signatures for intelligent mobile agents committing “smaller than” condition is studied, which shows the applicability of set signatures on small sets. [ABSTRACT FROM AUTHOR]

With the development of various cryptographic primitives deployed on insecure devices, key exposure seems inevitable. Generalized from forward-secure signatures and key-insulated signatures, intrusion-resilient signatures (IRSs) was first introduced by Itkis and Reyzin, which help us to minimize the damage of key exposure. IRSs provide the unforgeability for the past and future time periods unless both the signer and the home base modules were compromised simultaneously (even in this worst case, IRSs preserve the unforgeability for the past periods). In this paper, we propose a practical generic construction for IRSs. By applying our proposal, one can simply transform any signature scheme to a practical intrusion-resilient signature scheme. In particular, we present a concrete paradigm from linear feedback shift register (LFSR). Our LFSR-based paradigm's base and signer secret keys can be reduced to just a half length of the regular ones, which is useful to save the communication and storage costs. Moreover, if the underlying signature is unforgeable in the standard model, then our construction is also intrusion-resilient in the standard model without any extra assumptions. [ABSTRACT FROM AUTHOR]

The Fiat-Shamir paradigm for transforming identification schemes into signature schemes has been popular since its introduction because it yields efficient signature schemes, and has been receiving renewed interest of late as the main tool in deriving forward-secure signature schemes. In this paper, minimal (meaning necessary and sufficient) conditions on the identification scheme to ensure security of the signature scheme in the random oracle model are determined, both in the usual and in the forward-secure cases. Specifically, it is shown that the signature scheme is secure (respectively, forward-secure) against chosen-message attacks in the random oracle model if and only if the underlying identification scheme is secure (respectively, forward-secure) against impersonation under passive (i.e., eaves-dropping only) attacks, and has its commitments drawn at random from a large space. An extension is proven incorporating a random seed into the Fiat-Shamir transform so that the commitment space assumption may be removed. [ABSTRACT FROM AUTHOR]

Forward secure signature can protect the security of signatures previous to the key exposure. Server-assisted signature is a special digital signature in which the signer allies one server to produce the signatures. In this paper, server-assisted forward-secure threshold signature is proposed. The system is composed of n 1 servers and n 2 users. Each user and each server holds a partial secret, respectively. To produce a valid signature, users and servers need to cooperate to complete the work. The partial secrets of the users and servers are updated by a one-way function at regular intervals, while the public key is always fixed. Even if all the current partial secrets are exposed, the signatures pertaining to previous periods are still valid. [ABSTRACT FROM AUTHOR]

Yoon and Yoo recently proposed a robust authenticated encryption scheme and claimed their scheme has the properties of forward secrecy and confidentiality. The current paper, however, points out that Yoon-Yoo's scheme also can not provide forward secrecy and confidentiality such that any adversary can easily recover the transferred message. Based on intractability of reversing the one-way hash function and discrete logarithm problem, an improved authenticated encryption scheme with messages linkage is proposed. The above security faults get solved perfectly. The new scheme is proven to satisfy all the basic security requirements of the authenticated encryption scheme. And by the concrete comparison, it has the similar efficiency of the original scheme. [ABSTRACT FROM AUTHOR]

Rapid distribution of newly released confidential information is often impeded by network traffic jams, especially when the confidential information is either crucial or highly prized. This is the case for stock market values, blind auction bidding amounts, many large corporations'strategic business plans, certain news agencies'timed publications, and some licensed software updates. Hierarchical time-based information release (HTIR) schemes enable the gradual distribution of encrypted confidential information to large, distributed, (potentially) hierarchically structured user communities, and the subsequent publication of corresponding short decryption keys, at a predetermined time, so that users can rapidly access the confidential information. This paper presents and analyzes the efficiency of a novel HTIR scheme. [ABSTRACT FROM AUTHOR]

Abstract: We propose the concept of fine-grained forward-secure signature schemes. Such signature schemes not only provide non-repudiation w.r.t. past time periods the way ordinary forward-secure signature schemes do but, in addition, allow the signer to specify which signatures of the current time period remain valid when revoking the public key. This is an important advantage if the signer produces many signatures per time period as otherwise the signer would have to re-issue those signatures (and possibly re-negotiate the respective messages) with a new key. Apart from a formal model for fine-grained forward-secure signature schemes, we present practical schemes and prove them secure under the strong RSA assumption only, i.e., we do not resort to the random oracle model to prove security. As a side-result, we provide an ordinary forward-secure scheme whose key-update time is significantly smaller than that of known schemes which are secure without assuming random oracles. [Copyright &y& Elsevier]

A group signature scheme allows a group member to sign a message anonymously on behalf of the group. In case of a dispute, the group manager can reveal the actual identity of signer. In this paper, we propose a novel group signature satisfying the regular requirements. Furthermore, it also achieves the following advantages: (1) the size of signature is independent of the number of group members; (2) the group public key is constant; (3) Addition and Revocation of group members are convenient; (4) it enjoys forward security; (5) The total computation cost of signature and verification requires only 8 modular exponentiations. Hence, our scheme is very practical in many applications, especially for the dynamic large group applications. [ABSTRACT FROM AUTHOR]

Abstract: Forward-secure signature schemes address the key exposure problem, in which all previously generated signatures are still considered to be valid even after the secret key is compromised. Multisignature scheme allow any subgroup of a group of users to jointly sign a document such that a verifier is convinced that each member of the subgroup participated in signing. Such schemes are very important technologies in this highly group-oriented society. Blind signature scheme are protocols for obtaining a signature from a signer, but the signer can neither learn the messages he/she sign nor the signatures the recipients obtain afterward. Such schemes are very important technologies in privacy oriented e-commerce applications. In this paper, we propose a forward-secure multisignature scheme and a forward-secure blind signature scheme. Our constructions are based on the recently proposed forward-secure signature scheme by bilinear pairings. [Copyright &y& Elsevier]

By combining the concepts of self-certified public key and signature with message recovery, Tseng et al. proposed a self-certified public key signature scheme with message recovery. The proposed scheme has two properties that the signer''s public key can simultaneously be authenticated in verifying the signature and the receiver also obtains the message. Based on the proposed scheme, they further presented two variants: one is an authenticated encryption scheme that only allows a specified receiver to verify and recover the message. The other scheme is the authenticated encryption scheme with message linkages, which is used to transmit large message. In this paper, we first propose an insider forgery attack, which means that the security of the authenticated encryption scheme is not as good as the Girault schemes. Then we point out that these schemes do not have nonrepudiation. In a case of dispute, neither the sender nor the receiver can convince arbiters if the signature is valid, unless they reveal their Diffie–Hellman key, which would destroy forward security. Finally we propose an improvement to these schemes to overcome the weakness. [Copyright &y& Elsevier]

Based on the concepts of elliptic curve cryptosystem and self-certified public key, Tzeng and Hwang recently published a digital signature scheme with message recovery and its variants based on elliptic curve discrete logarithm problems (ECDLP). The public key and the identity of users can be authenticated simultaneously in recovering messages. In this paper, we first show that the proposed schemes are only applicable for messages with enough redundancy. We also propose an insider forgery attack, which means that the security of the proposed authenticated encryption scheme is not as good as the Girault''s self-certified public key scheme. Second, we show that the proposed schemes do not satisfy forward security. Then we point out that these schemes do not have nonrepudiation. In a case of dispute, neither the sender nor the receiver can convince arbiters if the signature is valid, unless they reveal their Diffie–Hellman key, which would also destroy the forward security. Finally, we propose an improvement to these schemes to overcome these weaknesses and analyse the security of the improvement. [Copyright &y& Elsevier]

In this paper, we point out that Libert and Quisquater's signcryption scheme cannot provide public verifiability. Then we present a new identity based signcryption scheme using quadratic residue and pairings over elliptic curves. It combines the functionalities of both public verifiability and forward security at the same time. Under the Bilinear Diffie-Hellman and quadratic residue assumption, we describe the new scheme that is more secure and can be some-what more efficient than Libert and Quisquater's one. [ABSTRACT FROM AUTHOR]

Summary: To ensure the intactness of the stored data in cloud, numerous data public auditing mechanisms have been presented. However, most of these existing solutions suffer from several flaws: (a) identity privacy and data privacy of data owner are inevitably revealed to the auditor in the auditing process; (b) the existing public auditing mechanisms with resisting key exposure are only proved in the random oracle model. To address the problems above, in this paper, we propose an achieving identity‐and‐data privacy public auditing protocol with forward security in the standard model by incorporating knowledge proof signature, ring signature, and forward security technique. And then, we formalize the security model of forward security and anonymity of identity, in which the adversary is allowed to query private keys of some ring members. It can provide stronger security. Thus, our proposed scheme can not only achieve data owner's identity privacy and data privacy but also provide forward security for data owner's secret key. To the best of our knowledge, it is the first preserving privacy of identity‐and‐data public auditing scheme with forward security that is provably secure in the standard model. The security of the scheme is related to the computational Diffie–Hellman (CDH) problem and the subgroup decision problem. Finally, our scheme is simulatively tested; experimental results demonstrate that our mechanism is very efficient in terms of overall performance. [ABSTRACT FROM AUTHOR]

Most of existing schemes can't simultaneously provide with public verifiability and forward security. To solve this problem, based on the difficulties of discrete logarithm problem on the cyclic group Zp and the intractability of reversing a one-way hash function, this paper presented a public verifiable signcryption scheme with forward security. In this scheme, the verification process didn't need the sender' s private key, in the transmission, a parameter (r) was hided in the index of g, so attacked who obtained the sender's private key couldn't get any secret information between these participates before this communication. By these methods the scheme achieved public verifiability and forward security and made up the short coming of most existing schemes that can't simultaneously provide with public verifiability and forward security. And furthermore, authentication and message recovery was not separated, but in the process of public verify, the message confidentiality won't be damaged, this made the scheme have higher security and more widely applications. [ABSTRACT FROM AUTHOR]

The article comments on the papers selected from the proceedings of the Eighth International Information Security Conference from September 20 to September 23,2005 in Singapore. The paper "Execution Transactions for Defending Against Software Failures” by Stelios Sidiroglou and Angelos Keromytis examines the problem of containing buffer overflow attacks in a safe and efficient manner.

In 2014, Chen et al. proposed a one-way hash self-healing group key distribution scheme for resource-constrained wireless networks in the journal of Sensors (14(14):24358-24380, doi: 10.3390/ s141224358). They asserted that their Scheme 2 achieves mt-revocation capability, mt-wise forward secrecy, any-wise backward secrecy and has mt-wise collusion attack resistance capability. Unfortunately, this paper pointed out that their scheme does not satisfy the forward security, mt-revocation capability and mt-wise collusion attack resistance capability.

In 2009, Han et al. proposed an efficient threshold self-healing key distribution scheme with sponsorization for infrastructureless wireless networks. They claimed that the key distribution scheme satisfies the forward security, i.e., any internal user who has been revoked can not generate a new session key. In this paper,an attack method against this key distribution scheme's forward security was presented. Furthermore, this attack method can also be applied to this scheme's backward security.Thus,the original threshold self-healing key distribution scheme is insecure. [ABSTRACT FROM PUBLISHER]