21,209 research outputs found
Securely Instantiating Cryptographic Schemes Based on the Learning with Errors Assumption
Since its proposal by Regev in 2005, the Learning With Errors (LWE) problem was used as the underlying problem for a great variety of schemes. Its applications are many-fold, reaching from basic and highly practical primitives like key exchange, public-key encryption, and signature schemes to very advanced solutions like fully homomorphic encryption, group signatures, and identity based encryption.
One of the underlying reasons for this fertility is the flexibility with that LWE can be instantiated. Unfortunately, this comes at a cost: It makes selecting parameters for cryptographic applications complicated. When selecting parameters for a new LWE-based primitive, a researcher has to take the influence of several parameters on the efficiency of the scheme and the runtime of a variety of attacks into consideration. In fact, the missing trust in the concrete hardness of LWE is one of the main problems to overcome to bring LWE-based schemes to practice.
This thesis aims at closing the gap between the theoretical knowledge of the hardness of LWE, and the concrete problem of selecting parameters for an LWE-based scheme. To this end, we analyze the existing methods to estimate the hardness of LWE, and introduce new estimation techniques where necessary. Afterwards, we show how to transfer this knowledge into instantiations that are at the same time secure and efficient. We show this process on three examples:
- A highly optimized public-key encryption scheme for embedded devices that is based on a variant of Ring-LWE.
- A practical signature scheme that served as the foundation of one of the best lattice-based signature schemes based on standard lattices.
- An advanced public-key encryption scheme that enjoys the unique property of natural double hardness based on LWE instances similar to those used for fully homomorphic encryption
Year 2010 Issues on Cryptographic Algorithms
In the financial sector, cryptographic algorithms are used as fundamental techniques for assuring confidentiality and integrity of data used in financial transactions and for authenticating entities involved in the transactions. Currently, the most widely used algorithms appear to be two-key triple DES and RC4 for symmetric ciphers, RSA with a 1024-bit key for an asymmetric cipher and a digital signature, and SHA-1 for a hash function according to international standards and guidelines related to the financial transactions. However, according to academic papers and reports regarding the security evaluation for such algorithms, it is difficult to ensure enough security by using the algorithms for a long time period, such as 10 or 15 years, due to advances in cryptanalysis techniques, improvement of computing power, and so on. To enhance the transition to more secure ones, National Institute of Standards and Technology (NIST) of the United States describes in various guidelines that NIST will no longer approve two-key triple DES, RSA with a 1024-bit key, and SHA-1 as the algorithms suitable for IT systems of the U.S. Federal Government after 2010. It is an important issue how to advance the transition of the algorithms in the financial sector. This paper refers to issues regarding the transition as Year 2010 issues in cryptographic algorithms. To successfully complete the transition by 2010, the deadline set by NIST, it is necessary for financial institutions to begin discussing the issues at the earliest possible date. This paper summarizes security evaluation results of the current algorithms, and describes Year 2010 issues, their impact on the financial industry, and the transition plan announced by NIST. This paper also shows several points to be discussed when dealing with Year 2010 issues.Cryptographic algorithm; Symmetric cipher; Asymmetric cipher; Security; Year 2010 issues; Hash function
Digital forensics formats: seeking a digital preservation storage format for web archiving
In this paper we discuss archival storage formats from the point of view of digital curation and
preservation. Considering established approaches to data management as our jumping off point, we
selected seven format attributes which are core to the long term accessibility of digital materials.
These we have labeled core preservation attributes. These attributes are then used as evaluation
criteria to compare file formats belonging to five common categories: formats for archiving selected
content (e.g. tar, WARC), disk image formats that capture data for recovery or installation
(partimage, dd raw image), these two types combined with a selected compression algorithm (e.g.
tar+gzip), formats that combine packing and compression (e.g. 7-zip), and forensic file formats for
data analysis in criminal investigations (e.g. aff, Advanced Forensic File format). We present a
general discussion of the file format landscape in terms of the attributes we discuss, and make a
direct comparison between the three most promising archival formats: tar, WARC, and aff. We
conclude by suggesting the next steps to take the research forward and to validate the observations
we have made
Enhancing Data Security by Making Data Disappear in a P2P Systems
This paper describes the problem of securing data by making it disappear
after some time limit, making it impossible for it to be recovered by an
unauthorized party. This method is in response to the need to keep the data
secured and to protect the privacy of archived data on the servers, Cloud and
Peer-to-Peer architectures. Due to the distributed nature of these
architectures, it is impossible to destroy the data completely. So, we store
the data by applying encryption and then manage the key, which is easier to do
as the key is small and it can be hidden in the DHT (Distributed hash table).
Even if the keys in the DHT and the encrypted data were compromised, the data
would still be secure. This paper describes existing solutions, points to their
limitations and suggests improvements with a new secure architecture. We
evaluated and executed this architecture on the Java platform and proved that
it is more secure than other architectures.Comment: 18 page
Experimental Demonstration of Quantum Fully Homomorphic Encryption with Application in a Two-Party Secure Protocol
A fully homomorphic encryption system hides data from unauthorized parties,
while still allowing them to perform computations on the encrypted data. Aside
from the straightforward benefit of allowing users to delegate computations to
a more powerful server without revealing their inputs, a fully homomorphic
cryptosystem can be used as a building block in the construction of a number of
cryptographic functionalities. Designing such a scheme remained an open problem
until 2009, decades after the idea was first conceived, and the past few years
have seen the generalization of this functionality to the world of quantum
machines. Quantum schemes prior to the one implemented here were able to
replicate some features in particular use-cases often associated with
homomorphic encryption but lacked other crucial properties, for example,
relying on continual interaction to perform a computation or leaking
information about the encrypted data. We present the first experimental
realisation of a quantum fully homomorphic encryption scheme. We further
present a toy two-party secure computation task enabled by our scheme. Finally,
as part of our implementation, we also demonstrate a post-selective two-qubit
linear optical controlled-phase gate with a much higher post-selection success
probability (1/2) when compared to alternate implementations, e.g. with
post-selective controlled- or controlled- gates (1/9).Comment: 11 pages, 16 figures, 2 table
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