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Lower Bounds for Linear Locally Decodable Codes and Private Information Retrieval
Montreal, Canada May 21-May 24
DOI Bookmark: http://doi.ieeecomputersociety.org/10.1109/CCC.2002.100435317th Annual IEEE Conference on Comput ...
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Oded Goldreich, Weizmann Institute of Science
Howard Karloff, AT&T Labs
Luca Trevisan, University of California at Berkeley
We prove that if a linear error-correcting code C:\{0,1\}^n\to\{0,1\}^m is such that a bit of the message can be probabilistically reconstructed by looking at two entries of a corrupted codeword, then m = 2^{\Omega(n)}. We also present several extensions of this result.We show a reduction from the complexity of one-round, information-theoretic Private Information Retrieval Systems (with two servers) to Locally Decodable Codes, and conclude that if all the servers' answers are linear combinations of the database content, then t = \Omega(n/2^a), where t is the length of the user's query and a is the length of the servers' answers. Actually, 2^a can be replaced by O(a^k), where k is the number of bit locations in the answer that are actually inspected in the reconstruction.
Index Terms:
Error Correcting Codes, Linear Codes, Private Information Retrieval
Citation:
Oded Goldreich, Howard Karloff, Leonard J. Schulman, Luca Trevisan, "Lower Bounds for Linear Locally Decodable Codes and Private Information Retrieval," ccc, pp.0175, 17th Annual IEEE Conference on Computational Complexity (CCC'02), 2002
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