Method to encrypt a sensitive data secure against template attacks

摘要

The present invention relates to a method to encrypt a sensitive data constituted by words (Wi) using a ciphering algorithm, said ciphering algorithm having at least one round (n) comprising at least two operations (Ok or Oki) to be executed on all words (Wi), said operations (Ok or Oki) being switchable thanks to operation status flags (SF), additional buffer (B) and additional operations (AdO), said method comprising the steps of:
- randomly determining (S1) an order (RND) for said operations (Ok or Oki) in each round (n);
- applying (S2) operations (Ok or Oki) on all words (Wi) of the sensitive data according to the determined order (RND) in each round (n);
- performing (S3) additional operations (AdO) in case of need;
- updating (S4) operation status flags (SF) and additional buffer (B) depending on the application of the operations (Ok or Oki).