2,241 research outputs found
Naturally Rehearsing Passwords
We introduce quantitative usability and security models to guide the design
of password management schemes --- systematic strategies to help users create
and remember multiple passwords. In the same way that security proofs in
cryptography are based on complexity-theoretic assumptions (e.g., hardness of
factoring and discrete logarithm), we quantify usability by introducing
usability assumptions. In particular, password management relies on assumptions
about human memory, e.g., that a user who follows a particular rehearsal
schedule will successfully maintain the corresponding memory. These assumptions
are informed by research in cognitive science and validated through empirical
studies. Given rehearsal requirements and a user's visitation schedule for each
account, we use the total number of extra rehearsals that the user would have
to do to remember all of his passwords as a measure of the usability of the
password scheme. Our usability model leads us to a key observation: password
reuse benefits users not only by reducing the number of passwords that the user
has to memorize, but more importantly by increasing the natural rehearsal rate
for each password. We also present a security model which accounts for the
complexity of password management with multiple accounts and associated
threats, including online, offline, and plaintext password leak attacks.
Observing that current password management schemes are either insecure or
unusable, we present Shared Cues--- a new scheme in which the underlying secret
is strategically shared across accounts to ensure that most rehearsal
requirements are satisfied naturally while simultaneously providing strong
security. The construction uses the Chinese Remainder Theorem to achieve these
competing goals
Security in Wireless Local Area Networks (WLANs)
Major research domains in the WLAN security include: access control & data frame protection, lightweight authentication and secure handoff. Access control standard like IEEE 802.11i provides flexibility in user authentication but on the other hand fell prey to Denial of Service (DoS) attacks. For Protecting the data communication between two communicating devices—three standard protocols i.e., WEP (Wired Equivalent Privacy), TKIP (Temporal Key Integrity Protocol) and AES-CCMP (Advanced Encryption Standard—Counter mode with CBC-MAC protocol) are used. Out of these, AES-CCMP protocol is secure enough and mostly used in enterprises. In WLAN environment lightweight authentication is an asset, provided it also satisfies other security properties like protecting the authentication stream or token along with securing the transmitted message. CAPWAP (Control and Provisioning of Wireless Access Points), HOKEY (Hand Over Keying) and IEEE 802.11r are major protocols for executing the secure handoff. In WLANs, handoff should not only be performed within time limits as required by the real time applications but should also be used to transfer safely the keying material for further communication. In this chapter, a comparative study of the security mechanisms under the above-mentioned research domains is provided
Updatable Oblivious Key Management for Storage Systems
We introduce Oblivious Key Management Systems (KMS) as a more secure alternative to traditional wrapping-based KMS that form the backbone of key management in large-scale data storage deployments. The new system, that builds on Oblivious Pseudorandom Functions (OPRF), hides keys and object identifiers from the KMS, offers unconditional security for key transport, provides key verifiability, reduces storage, and more. Further, we show how to provide all these features in a distributed threshold implementation that enhances protection against server compromise.
We extend this system with updatable encryption capability that supports key updates (known as key rotation) so that upon the periodic change of OPRF keys by the KMS server, a very efficient update procedure allows a client of the KMS service to non-interactively update all its encrypted data to be decryptable only by the new key. This enhances security with forward and post-compromise security, namely, security against future and past compromises, respectively, of the client\u27s OPRF keys held by the KMS. Additionally, and in contrast to traditional KMS, our solution supports public key encryption and dispenses with any interaction with the KMS for data encryption (only decryption by the client requires such communication).
Our solutions build on recent work on updatable encryption but with significant enhancements applicable to the remote KMS setting. In addition to the critical security improvements, our designs are highly efficient and ready for use in practice. We report on experimental implementation and performance
Contextualizing Alternative Models of Secret Sharing
A secret sharing scheme is a means of distributing information to a set of players such that any authorized subset of players can recover a secret and any unauthorized subset does not learn any information about the secret. In over forty years of research in secret sharing, there has been an emergence of new models and extended capabilities of secret sharing schemes. In this thesis, we study various models of secret sharing and present them in a consistent manner to provide context for each definition. We discuss extended capabilities of secret sharing schemes, including a comparison of methods for updating secrets via local computations on shares and an analysis of approaches to reproducing/repairing shares. We present an analysis of alternative adversarial settings which have been considered in the area of secret sharing. In this work, we present a formalization of a deniability property which is inherent to some classical secret sharing schemes. We provide new, game-based definitions for different notions of verifiability and robustness. By using consistent terminology and similar game-based definitions, we are able to demystify the subtle differences in each notion raised in the literature
A framework for World Wide Web client-authentication protocols
Existing client-authentication protocols deployed on the World Wide Web today are based on conventional distributed systems and fail to address the problems specific to the application domain. Some of the protocols restrict the mobility of the client by equating user identity to a machine or network address, others depend on sound password management strategies, and yet others compromise the privacy of the user by transmitting personal information for authentication. We introduce a new framework for client-authentication by separating two goals that current protocols achieve simultaneously: 1. Maintain persistent sense of identity across different sessions. 2. Prove facts about the user to the site. These problems are independent, in the sense that any protocol for solving the first problem can be combined with any protocol for solving the second. Separation of the two purposes opens up the possibility of designing systems which balance two conflicting goals, authentication and anonymity. We propose a solution to the first problem, based on the Digital Signature Standard. The implications of this framework from the point of view of user privacy are examined. The paper is concluded with suggestions for integrating the proposed scheme into the existing WWW architecture
Secure Identification in Social Wireless Networks
The applications based on social networking have brought revolution towards social life and are continuously gaining popularity among the Internet users. Due to the advanced computational resources offered by the innovative hardware and nominal subscriber charges of network operators, most of the online social networks are transforming into the mobile domain by offering exciting applications and games exclusively designed for users on the go. Moreover, the mobile devices are considered more personal as compared to their desktop rivals, so there is a tendency among the mobile users to store sensitive data like contacts, passwords, bank account details, updated calendar entries with key dates and personal notes on their devices.
The Project Social Wireless Network Secure Identification (SWIN) is carried out at Swedish Institute of Computer Science (SICS) to explore the practicality of providing the secure mobile social networking portal with advanced security features to tackle potential security threats by extending the existing methods with more innovative security technologies. In addition to the extensive background study and the determination of marketable use-cases with their corresponding security requirements, this thesis proposes a secure identification design to satisfy the security dimensions for both online and offline peers. We have implemented an initial prototype using PHP Socket and OpenSSL library to simulate the secure identification procedure based on the proposed design. The design is in compliance with 3GPP‟s Generic Authentication Architecture (GAA) and our implementation has demonstrated the flexibility of the solution to be applied independently for the applications requiring secure identification. Finally, the thesis provides strong foundation for the advanced implementation on mobile platform in future
A Practical Framework for Storing and Searching Encrypted Data on Cloud Storage
Security has become a significant concern with the increased popularity of
cloud storage services. It comes with the vulnerability of being accessed by
third parties. Security is one of the major hurdles in the cloud server for the
user when the user data that reside in local storage is outsourced to the
cloud. It has given rise to security concerns involved in data confidentiality
even after the deletion of data from cloud storage. Though, it raises a serious
problem when the encrypted data needs to be shared with more people than the
data owner initially designated. However, searching on encrypted data is a
fundamental issue in cloud storage. The method of searching over encrypted data
represents a significant challenge in the cloud.
Searchable encryption allows a cloud server to conduct a search over
encrypted data on behalf of the data users without learning the underlying
plaintexts. While many academic SE schemes show provable security, they usually
expose some query information, making them less practical, weak in usability,
and challenging to deploy. Also, sharing encrypted data with other authorized
users must provide each document's secret key. However, this way has many
limitations due to the difficulty of key management and distribution.
We have designed the system using the existing cryptographic approaches,
ensuring the search on encrypted data over the cloud. The primary focus of our
proposed model is to ensure user privacy and security through a less
computationally intensive, user-friendly system with a trusted third party
entity. To demonstrate our proposed model, we have implemented a web
application called CryptoSearch as an overlay system on top of a well-known
cloud storage domain. It exhibits secure search on encrypted data with no
compromise to the user-friendliness and the scheme's functional performance in
real-world applications.Comment: 146 Pages, Master's Thesis, 6 Chapters, 96 Figures, 11 Table
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