On the list and bounded distance decodability of the Reed-Solomon codes

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Title: On the list and bounded distance decodability of the Reed-Solomon codes
Authors: Qi Cheng, Daqing Wan
Contributors: The Pennsylvania State University CiteSeerX Archives
Source: http://www.math.uci.edu/~dwan/code.pdf.
Publisher Information: IEEE Computer Society
Publication Year: 2004
Collection: CiteSeerX
Description: For an error-correcting code and a distance bound, the list decoding problem is to compute all the codewords within a given distance to a received message. The bounded distance decoding problem is to find one codeword if there is at least one codeword within the given distance, or to output the empty set if there is not. Obviously the bounded distance decoding problem is not as hard as the list decoding problem. For a Reed-Solomon code [n, k]q, a simple counting argument shows that for any integer 0 < g < n, there exists at least one Hamming ball of radius n−g, which contains at least � � n g−k g /q many codewords. Let ˆg(n, k, q) be the smallest positive integer g such that � � n g−k g /q < 1. One knows that k ≤ ˆg(n, k, q) ≤ √ nk ≤ n. For the distance bound up to n − √ nk, it is well known that both the list and bounded distance decoding can be solved efficiently. For the distance bound between n − √ nk and n − ˆg(n, k, q), we do not know whether the Reed-Solomon code is list, or bounded distance decodable, nor do we know whether there are polynomially many codewords in all balls of the radius. It is generally believed that the answers to both questions are no. There are public key cryptosystems proposed recently, whose security is based on the assumptions. In this paper, we prove: (1) List decoding can not be done for radius n − ˆg(n, k, q) or larger, otherwise the discrete logarithm over F q ˆg(n,k,q)−k is easy. (2) Let h and g be
Document Type: text
File Description: application/pdf
Language: English
Relation: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.78.3972; http://www.math.uci.edu/~dwan/code.pdf
Availability: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.78.3972
http://www.math.uci.edu/~dwan/code.pdf
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Accession Number: edsbas.BB500C99
Database: BASE
Description
Abstract:For an error-correcting code and a distance bound, the list decoding problem is to compute all the codewords within a given distance to a received message. The bounded distance decoding problem is to find one codeword if there is at least one codeword within the given distance, or to output the empty set if there is not. Obviously the bounded distance decoding problem is not as hard as the list decoding problem. For a Reed-Solomon code [n, k]q, a simple counting argument shows that for any integer 0 < g < n, there exists at least one Hamming ball of radius n−g, which contains at least � � n g−k g /q many codewords. Let ˆg(n, k, q) be the smallest positive integer g such that � � n g−k g /q < 1. One knows that k ≤ ˆg(n, k, q) ≤ √ nk ≤ n. For the distance bound up to n − √ nk, it is well known that both the list and bounded distance decoding can be solved efficiently. For the distance bound between n − √ nk and n − ˆg(n, k, q), we do not know whether the Reed-Solomon code is list, or bounded distance decodable, nor do we know whether there are polynomially many codewords in all balls of the radius. It is generally believed that the answers to both questions are no. There are public key cryptosystems proposed recently, whose security is based on the assumptions. In this paper, we prove: (1) List decoding can not be done for radius n − ˆg(n, k, q) or larger, otherwise the discrete logarithm over F q ˆg(n,k,q)−k is easy. (2) Let h and g be