On the Theory and Practice of Personal Digital Signatures

Damgård, Ivan; Mikkelsen, Gert Læssøe

doi:10.1007/978-3-642-00468-1_16

Cited by 10 publications

(10 citation statements)

References 18 publications

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“…There is a large body of cryptographic literature dealing with threshold digital signatures [1,22,23,26,33,44], where the security of a signature scheme is increased by splitting the signer player into several players. In this way one obtains schemes that stay secure even in case one or more (up to a certain threshold) of these players get corrupted.…”

Section: Introductionmentioning

confidence: 99%

“…An important work in this vein (which however, still restricts to signatures) is due to Damgård and Mikkelsen [23]. They introduce a model where the human user in the context of a signature scheme is represented not by a single player, as often done in cryptographic literature, but by several players thereby decoupling the user and his actual equipment (e.g., a smart card and a PC).…”

Section: Introductionmentioning

confidence: 99%

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Efficient Threshold Zero-Knowledge with Applications to User-Centric Protocols

Keller

Mikkelsen

Rupp³

2012

Lecture Notes in Computer Science

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Abstract. In this paper, we investigate on threshold proofs, a framework for distributing the prover's side of interactive proofs of knowledge over multiple parties. Interactive proofs of knowledge (PoK) are widely used primitives of cryptographic protocols, including important user-centric protocols, such as identification schemes, electronic cash (e-cash), and anonymous credentials. We present a security model for threshold proofs of knowledge and develop threshold versions of well-known primitives such as range proofs, zero-knowledge proofs for preimages of homomorphisms (which generalizes PoKs of discrete logarithms, representations, p-th roots, etc.), as well as OR statements. These building blocks are proven secure in our model. Furthermore, we apply the developed primitives and techniques in the context of user-centric protocols. In particular, we construct distributed-user variants of Brands' e-cash system and the bilinear anonymous credential scheme by Camenisch and Lysyanskaya. Distributing the user party in such protocols has several practical advantages: First, the security of a user can be increased by sharing secrets and computations over multiple devices owned by the user. In this way, losing control of a single device does not result in a security breach. Second, this approach also allows groups of users to jointly control an application (e.g., a joint e-cash account), not giving a single user full control. The distributed versions of the protocols we propose in this paper are relatively efficient (when compared to a general MPC approach). In comparison to the original protocols only the prover's (or user's) side is modified while the other side stays untouched. In particular, it is oblivious to the other party whether it interacts with a distributed prover (or user) or one as defined in the original protocol.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Efficient Threshold Zero-Knowledge with Applications to User-Centric Protocols

Keller

Mikkelsen

Rupp³

2012

Lecture Notes in Computer Science

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“…For instance, in the framework for distributed RSA signatures suggested by the authors [12], it is natural to run a 3-party protocol where a PC, a server and a mobile device held by the user execute the protocol.…”

Section: Introductionmentioning

confidence: 99%

Efficient, Robust and Constant-Round Distributed RSA Key Generation

Damgård

Mikkelsen

2010

Theory of Cryptography

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“…This protocol prevented man-in-the-middle attacks and provided true two-factor security. The ITSCI project's security researchers published descriptions, explanations, and security considerations about the protocol in [24,25].The protocol was based on so-called public key cryptography, where identities are tied to a pair consisting of a public and a private key. The private key has to be kept secret and is normally protected by a password.…”

mentioning

confidence: 99%

“…This was accomplished by a scheme similar to the use of PIN codes and puc/puk codes (Personal Unblocking Codes, Pin Unlock Codes, or Pin Unlock Keys) which were known from GSM cell phones (Groupe Spécial Mobile). Read more about the security protocol and cryptography details in [24,25].How the private keys would be generated and installed on the server and the cell phone was also considered. Security mechanisms were often compromised at the time of installation.…”

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confidence: 99%

While working around security

Mathiasen

Pedersen

Bødker

2011

Proceedings of the 3rd International Conference on Human Computer Interaction - IndiaHCI '11

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Users of technology encounter various IT security mechanisms in their everyday lives. If these mechanisms fail to support everyday activities, they either get in the way, or the users find a way to work around them. Even though users manage to carry out everyday activities by using substandard IT security mechanisms or via workarounds, it will influence their experience of security. If researchers and designers only focus on IT security artifacts and fail to take the user experience into account, incorrect processes or workarounds will occur. Accordingly, to get users to follow the correct process may seem to be a criterion of success, even though it may yield a less appropriate experience of security.This dissertation deals with an improved understanding of IT security sensitive IT artifacts and presents three design methods, and a framework for addressing the complexities and contingencies of security experiences in design. The methods: Mobile probing, Prompted exploration workshops, and Acting out security involve potential future users in the process of designing IT security sensitive IT artifacts. Mobile probing collects narratives of user encounters with IT security. Prompted exploration workshops present the users with seven themes and involve them in the design of IT security sensitive IT artifacts. Acting out security lets users try out prototypes in situations where security handling is infrequent and quick. All three methods have been developed and deployed as an integral part of a research through design process. An everyday mobile digital signature solution has been designed, and the design problem, the design process, and the design results are presented in this dissertation.Several of my empirical findings show that the way users experience security does matter. Users' experiences of security influence the way they make sense of, assess, and handle IT security mechanisms. Moreover, I studied cases in which the users handled IT security sensitive technology in a secure way, but still had unwanted experiences of security. Through the developed design methods I was able to activate and access study participants' prior experiences of making sense of IT security sensitive technology. Moreover, the methods helped clarify users' immediate experience in an encounter with IT security sensitive technology. The findings were integrated into the design of a digital signature solution, and in this process I developed a framework for structuring empirical findings for the design of IT security sensitive IT artifacts. v Resume Hver dag møder mennesker IT-sikkerhed på mange forskellige måder. Nogle IT-sikkerhedsmekanismer er indrettet, så de ikke understøtter de aktiviteter, de indgår i. Enten kommer de i vejen og brugerne må opgive deres forehavende, eller også finder brugerne en måde at omgå sikkerheden på. Selv om brugerne formår at anvende IT på trods af at IT-sikkerhedsmekanismerne kommer i vejen, kan deres oplevelse af og erfaring med IT-sikkerhed sagtens vaere uhensigtsmaessig. Hvis forskere i og d...

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On the Theory and Practice of Personal Digital Signatures

Cited by 10 publications

References 18 publications

Efficient Threshold Zero-Knowledge with Applications to User-Centric Protocols

Efficient Threshold Zero-Knowledge with Applications to User-Centric Protocols

Efficient, Robust and Constant-Round Distributed RSA Key Generation

While working around security

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