Method to protect a cryptographic assembly by homographic masking
US8074076B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | May 11, 2005 |
| Grant date | Dec 6, 2011 |
| Priority date | — |
| Expiry date | Nov 16, 2028 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2209/046
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
This invention relates to a method to protect an assembly implementing a cryptographic calculation process which uses a homographic function f of type:f(z)=(az+b)/(cz+d) when (cz+d) is not equal to 0 andf(−d/c)=a/c the function f operating on masked variables, wherein, for any k, if x is an input and y=f(x+k) is an output of the function f, to pass directly from a masked value x+m_i (additive masking of type XOR) to a masked value y+m_j, the method consists in comprises of performing this operation using a composition of several transformations operating on GF(2^k) with addition of the infinite, defined as (ax+b)/(cx+d), and of transformations which exchange two points.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.