On the security of subspace subcodes of Reed-Solomon codes for public key encryption
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This article discusses the security of McEliece-like encryption schemes using subspace subcodes of Reed-Solomon codes, i.e. subcodes of Reed-Solomon codes over 𝔽_q^m whose entries lie in a fixed collection of 𝔽_q-subspaces of 𝔽_q^m. These codes appear to be a natural generalisation of Goppa and alternant codes and provide a broader flexibility in designing code based encryption schemes. For the security analysis, we introduce a new operation on codes called the twisted product which yields a polynomial time distinguisher on such subspace subcodes as soon as the chosen 𝔽_q-subspaces have dimension larger than m/2. From this distinguisher, we build an efficient attack which in particular breaks some parameters of a recent proposal due to Khathuria, Rosenthal and Weger.
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