The family of Information Dispersal Algorithms is applied to distributed systems for secure and reliable storage and transmission. In comparison with perfect secret sharing it achieves a significantly smaller memory overhead and better performance, but provides only incremental confidentiality. Therefore, even if it is not possible to explicitly reconstruct data from less than the required amount of fragments, it is still possible to deduce some information about the nature of data by looking at preserved data patterns inside a fragment. The idea behind this paper is to provide a lightweight data fragmentation scheme, that would combine the space efficiency and simplicity that could be find in Information Dispersal Algorithms with a computational level of data confidentiality.
The AONT-RS technique @cite_15 is similar to SSMS, as it combines symmetric encryption with data dispersal. It applies an all-or-nothing transform(AONT) @cite_5 to create @math fragments: encrypted data are divided into @math fragments and an additional fragment is generated by xor -ing hashes of these data fragments with the key used for encryption. Additional @math fragments are produced using a systematic Reed-Solomon error correction code. Data integrity is ensured by the use of a canary that is dispersed within the fragments.
@cite_5 @cite_15
1482576848 2048114999 2115652664 2015105729
Dispersing files across multiple sites yields a variety of obvious benefits, such as availability, proximity and reliability. Less obviously, it enables security to be achieved without relying on encryption keys. Standard approaches to dispersal either achieve very high security with correspondingly high computational and storage costs, or low security with lower costs. In this paper, we describe a new dispersal scheme, called AONT-RS, which blends an All-Or-Nothing Transform with Reed-Solomon coding to achieve high security with low computational and storage costs. We evaluate this scheme both theoretically and as implemented with standard open source tools. AONTRS forms the backbone of a commercial dispersed storage system, which we briefly describe and then use as a further experimental testbed. We conclude with details of actual deployments. In this paper, we provide a method to safely store a document in perhaps the most challenging settings, a highly decentralized replicated storage system where up to half of the storage servers may incur arbitrary failures, including alterations to data stored in them. Using an error correcting code (ECC), e.g., a Reed?Solomon code, one can take n pieces of a document, replace each piece with another piece of size larger by a factor of nn?2t+1 such that it is possible to recover the original set even when up to t of the larger pieces are altered. For t close to n 2 the space blowup factor of this scheme is close to n, and the overhead of an ECC such as the Reed?Solomon code degenerates to that of a trivial replication code. We show a technique to reduce this large space overhead for high values of t. Our scheme blows up each piece by a factor slightly larger than two using an erasure code which makes it possible to recover the original set using n 2?O(n d) of the pieces, where d?80 is a fixed constant. Then we attach to each piece O(d log n log d) additional bits to make it possible to identify a large enough set of unmodified pieces, with negligible error probability, assuming that at least half the pieces are unmodified and with low complexity. For values of t close to n 2 we achieve a large asymptotic space reduction over the best possible space blowup of any ECC in deterministic setting. Our approach makes use of a d-regular expander graph to compute the bits required for the identification of n 2?O(n d) good pieces. We study the security of individual bits in an RSA encrypted message EN(x). We show that given EN(x), predicting any single bit in x with only a nonnegligible advantage over the trivial guessing strategy, is (through a polynomial-time reduction) as hard as breaking RSA. Moreover, we prove that blocks of O(log log N) bits of x are computationally indistinguishable from random bits. The results carry over to the Rabin encryption scheme.Considering the discrete exponentiation function gx modulo p, with probability 1 − o(1) over random choices of the prime p, the analog results are demonstrated. The results do not rely on group representation, and therefore applies to general cyclic groups as well. Finally, we prove that the bits of ax + b modulo p give hard core predicates for any one-way function f.All our results follow from a general result on the chosen multiplier hidden number problem: given an integer N, and access to an algorithm Px that on input a random a i ZN, returns a guess of the ith bit of ax mod N, recover x. We show that for any i, if Px has at least a nonnegligible advantage in predicting the ith bit, we either recover x, or, obtain a nontrivial factor of N in polynomial time. The result also extends to prove the results about simultaneous security of blocks of O(log log N) bits. Secret key generation among wireless devices using physical layer information of radio channel has been an attractive alternative for ensuring security in mobile environments. Received signal strength (RSS) based secret key extraction gains much attention due to its easy accessibility in wireless infrastructure. However, the problem of using RSS to generate keys among multiple devices to ensure secure group communication in practice remains open. In this work, we propose a framework for collaborative key generation among multiple wireless devices leveraging RSS. To deal with mobile devices not within each other’s communication range, we employ relay nodes to achieve reliable key extraction. To enable secure group communication, two protocols are developed to perform collaborative group key generation via star and chain topologies respectively. We further provide the theoretic analysis on the achievable secrecy rate for both star and chain topologies in the presence of an eavesdropper. Our prototype development using MICAz motes and extensive experiments using fading trend based key extraction demonstrate the feasibility of using RSS for group key generation in both indoor and outdoor environments, and concurrently achieving a lower bit mismatch rate compared to existing studies.