In the setting of error correcting codes, Alice wants to send a message x ∈ {0,1}ⁿ to Bob via an encoding enc(x) that is resilient to error. In this work, we investigate the scenario where Bob is a low space decoder. More precisely, he receives Alice’s encoding enc(x) bit-by-bit and desires to compute some function f(x) in low space. A generic error-correcting code does not accomplish this because decoding is a very global process and requires at least linear space. Locally decodable codes partially solve this problem as they allow Bob to learn a given bit of x in low space, but not compute a generic function f. Our main result is an encoding and decoding procedure where Bob is still able to compute any such function f in low space when a constant fraction of the stream is corrupted. More precisely, we describe an encoding function enc(x) of length poly(n) so that for any decoder (streaming algorithm) A that on input x computes f(x) in space s, there is an explicit decoder B that computes f(x) in space s ⋅ polylog(n) as long as there were not more than 1/4 - ε fraction of (adversarial) errors in the input stream enc(x).
@InProceedings{gupta_et_al:LIPIcs.ITCS.2025.59, author = {Gupta, Meghal and Zhang, Rachel Yun}, title = {{Error Correction for Message Streams}}, booktitle = {16th Innovations in Theoretical Computer Science Conference (ITCS 2025)}, pages = {59:1--59:18}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-361-4}, ISSN = {1868-8969}, year = {2025}, volume = {325}, editor = {Meka, Raghu}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2025.59}, URN = {urn:nbn:de:0030-drops-226875}, doi = {10.4230/LIPIcs.ITCS.2025.59}, annote = {Keywords: error-correcting codes, streaming algorithms, space-efficient algorithms} }
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