| 摘要 |
The invention provides a method to reduce the risk of unauthorized access to the data, especially through side-channel observations. By using statistical techniques, herein called DPA or Differential Power Analysis. The method includes the steps of modifying the ciphering algorithm implementation to operate on mapped data, initially mapping of data, especially cryptographic keys, for storage, changing the data mapping from a prior data mapping by use of a secondary mapping, mapping incoming data for input to the modified algorithm implementation, and mapping data output from the modified algorithm for further use. The method results in enhanced secrecy. The data mapping and the secondary data mapping may be in the form of a lookup-table, an algorithm with mapping-selection data, or the like. The data mapping may be implemented as cascaded mappings. The operations of the original algorithm can be modulo-m addition, modulo-m multiplication or modulo-2 addition of two vectors of n compoments. In the last case, the mapping applied to at least one of the vectors has the form xi=Aix+bi wherein Ai is any matrix having an inverse and bi is a vector of n components.
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