[[alternative]]The Desing of Threshold Proxy Threshold Signature Schemes

計畫編號：NSC91-2213-E032-014研究期間：200208~200307研究經費：384,000[[sponsorship]]行政院國家科學委員

Designated Verifier Threshold Proxy Signature Scheme without Random Oracles

In a $(t,n)$ designated verifier threshold proxy signature \, scheme, an original signer can delegate his/her signing power to $n$ proxy signers such that any $t$ or more out of $n$ proxy signers can sign messages on behalf of the original signer but $t-1$ or less of the proxy signers cannot generate a valid proxy signature. Of course, the signature is issued for a designated receiver and therefore only the designated receiver can validate the proxy signature. In this paper, we propose a new designated verifier threshold proxy signature scheme and also show that the proposed scheme has provable security in the standard model. The security of proposed scheme is based on the $GBDH$ assumption and the proposed scheme satisfies all the security requirements of threshold proxy signature schemes

Cryptanalysis and Performance Evaluation of Enhanced Threshold Proxy Signature Scheme Based on RSA for Known Signers

In these days there are plenty of signature schemes such as the threshold proxy signature scheme (Kumar and Verma 2010). The network is a shared medium so that the weakness security attacks such as eavesdropping, replay attack, and modification attack. Thus, we have to establish a common key for encrypting/decrypting our communications over an insecure network. In this scheme, a threshold proxy signature scheme based on RSA, any or more proxy signers can cooperatively generate a proxy signature while or fewer of them cannot do it. The threshold proxy signature scheme uses the RSA cryptosystem to generate the private and the public key of the signers (Rivest et al., 1978). Comparison is done on the basis of time complexity, space complexity, and communication overhead. We compare the performance of four schemes (Hwang et al. (2003), Kuo and Chen (2005), Yong-Jun et al. (2007), and Li et al. (2007), with the performance of a scheme that has been proposed earlier by the authors of this paper. In the proposed scheme, both the combiner and the secret share holder can verify the correctness of the information that they are receiving from each other. Therefore, the enhanced threshold proxy signature scheme is secure and efficient against notorious conspiracy attacks

Fully Distributed Proxy Signature Schemes

In a proxy signature scheme, a potential signer delegates his signing capability to a proxy entity, who signs a message on behalf of the original signer. All the proposals of proxy signature schemes made until now have been based on Schnorr\u27s signature scheme. Threshold versions of these schemes have also been proposed, in which the power of the proxy signer is distributed among a group of players, in such a way that any subset with a minimum number (threshold) of players can sign a message on behalf of the original signer. We consider a model that is fully distributed, because we want to distribute not only the power of the proxy signer, but also the original signer ability to delegate his signing capability. Furthermore, we consider general structures, instead of only the threshold ones, for both the tolerated subsets of dishonest players and the subsets of honest players authorized to execute a valid instance of the protocol, and in both the original and the proxy signer entities. We find sufficient combinatorial conditions that these structures must satisfy in order to design a fully distributed, secure and robust proxy signature scheme for this general scenario. We propose such a scheme for this setting. It is also based on Schnorr\u27s signature scheme

Матричні співвідношення для параметрів, що характеризують стійкість блокових шифрів відносно диференціально-лінійного методу криптоаналізу

Метою роботи є побудова порогової проксi схеми цифрового пiдпису з використанням примiтивiв багатовимiрної криптографiї. Об’єктом дослiдження є iнформацiйнi процеси в системах захисту iнформацiї. Предметом дослiдження є побудова i аналiз коректностi та захищенностi порогової проксi схеми цифрового пiдпису на основi промiтивiв багатовимiрної криптографiї. В роботi дослiджено схеми цифрових пiдписiв у багатовимiрнiй криптографiї та актуальнiсть використання цифрових пiдписiв зi спецiальними властивостями, зокрема порогового пiдпису та проксi пiдпису. Розглянуто методи поєднання схеми цифрового пiдпису багатовимiрних криптосистем з вiдкритим ключем та схеми цифрового пiдпису зi спецiальними властивостями з дослiдженням коректностi i стiйкостi такої схеми цифрового пiдпису. Побудовано порогову проксi схему цифрового пiдпису з використанням примiтивiв багатовимiрної криптографiї та порогову проксi схему цифрового пiдпису на основi схеми пiдпису LUOV. Виконано аналiз коректностi та захищенностi побудованих схем цифрового пiдпису.The aim of the work is to build a threshold proxy scheme of digital signature using primitive multidimensional cryptography. The object of study is information processes in information security systems. The subject of the study is the construction and analysis of correctness and security of the threshold proxy of the digital signature scheme based on the promotes of multidimensional cryptography. The schemes of digital signatures in multidimensional cryptography and the relevance of using digital signatures with special properties, in particular threshold signature and proxy signature, are investigated in the work. Methods of combining the digital signature scheme of multivariate public key cryptosystems and the digital signature scheme with special properties with the study of the correctness and stability of such a digital signature scheme are considered. A digital proxy threshold scheme using multivariate cryptography primitives and a digital signature threshold proxy based on the LUOV signature scheme are constructed. An analysis of the correctness and security of the constructed digital signature schemes is performed

Побудова порогової проксі схеми цифрового підпису з використанням примітивів багатовимірної криптографії

Метою роботи є побудова порогової проксi схеми цифрового пiдпису з використанням примiтивiв багатовимiрної криптографiї. Об’єктом дослiдження є iнформацiйнi процеси в системах захисту iнформацiї. Предметом дослiдження є побудова i аналiз коректностi та захищенностi порогової проксi схеми цифрового пiдпису на основi промiтивiв багатовимiрної криптографiї. В роботi дослiджено схеми цифрових пiдписiв у багатовимiрнiй криптографiї та актуальнiсть використання цифрових пiдписiв зi спецiальними властивостями, зокрема порогового пiдпису та проксi пiдпису. Розглянуто методи поєднання схеми цифрового пiдпису багатовимiрних криптосистем з вiдкритим ключем та схеми цифрового пiдпису зi спецiальними властивостями з дослiдженням коректностi i стiйкостi такої схеми цифрового пiдпису. Побудовано порогову проксi схему цифрового пiдпису з використанням примiтивiв багатовимiрної криптографiї та порогову проксi схему цифрового пiдпису на основi схеми пiдпису LUOV. Виконано аналiз коректностi та захищенностi побудованих схем цифрового пiдпису.The aim of the work is to build a threshold proxy scheme of digital signature using primitive multidimensional cryptography. The object of study is information processes in information security systems. The subject of the study is the construction and analysis of correctness and security of the threshold proxy of the digital signature scheme based on the promotes of multidimensional cryptography. The schemes of digital signatures in multidimensional cryptography and the relevance of using digital signatures with special properties, in particular threshold signature and proxy signature, are investigated in the work. Methods of combining the digital signature scheme of multivariate public key cryptosystems and the digital signature scheme with special properties with the study of the correctness and stability of such a digital signature scheme are considered. A digital proxy threshold scheme using multivariate cryptography primitives and a digital signature threshold proxy based on the LUOV signature scheme are constructed. An analysis of the correctness and security of the constructed digital signature schemes is performed

Compartment-based and Hierarchical Threshold Delegated Verifiable Accountable Subgroup Multi-signatures

In this paper, we study the compartment-based and hierarchical delegation of signing power of the verifiable accountable subgroup multi-signature (vASM). ASM is a multi-signature in which the participants are accountable for the resulting signature, and the number of participants is not fixed. After Micali et al.’s and Boneh et al.’s ASM schemes, the verifiable-ASM (vASM) scheme with a verifiable group setup and more efficient verification phase was proposed recently. The verifiable group setup in vASM verifies the participants at the group setup phase. In this work, we show that the vASM scheme can also be considered as a proxy signature in which an authorized user (original signer, designator) delegates her signing rights to a single (or a group of) unauthorized user(s) (proxy signer). Namely, we propose four new constructions with the properties and functionalities of an ideal proxy signature and a compartment-based/hierarchical structure. In the first construction, we apply the vASM scheme recursively; in the second one, we use Shamir’s secret sharing (SSS) scheme; in the third construction, we use SSS again but in a nested fashion. In the last one, we use the hierarchical threshold secret sharing (HTSS) scheme for delegation. Then, we show the affiliation of our constructions to proxy signatures and compare our constructions with each other in terms of efficiency and security. Finally we compare the vASM scheme with the existing pairing-based proxy signature schemes

An Introduction to Multi-trapdoor Hash Functions and It's Applications

AbstractTrapdoor hash function is a highly useful cryptographic primitive for building a wide variety of novel signature schemes, like chameleon, online-offline, threshold, proxy, sanitizable and amortized signatures. These signature schemes form an essential part of the collection of mechanisms used for securing today's computing systems. With the advent of large-scale computing systems, like clouds, the need for building signature schemes that are both efficient and scalable has become increasingly important. This talk will discuss a cryptographic primitive, called a multi-trapdoor hash function, that is designed to address this need. The proposed hash function allows multiple entities to compute a collision with a given hash value. Using this unique property of multi-trapdoor hash functions, this talk will also present a preliminary design of aggregate signature and its application in securing clouds