公开(公告)号：EP3973659A1

公开(公告)日：2022-03-30

申请号：EP20715420.4

申请日：2020-04-07

申请人： Thales Dis France SAS

发明人： VIGILANT, David ,  LI, Xun ,  HOKUNI, Sami ,  RANTALA, Janne

IPC分类号： H04L9/00

公开(公告)号：EP4340293A1

公开(公告)日：2024-03-20

申请号：EP22306367.8

申请日：2022-09-16

申请人： THALES DIS FRANCE SAS

发明人： LI, Xun ,  VIGILANT, David

IPC分类号： H04L9/30

摘要： The present invention relates to a method for performing a cryptographic algorithm, performed by a cryptographic device comprising a cryptographic coprocessor comprising an integer multiplier, said cryptographic algorithm comprising a polynomial multiplication between a first input polynomial A[X] and a second input polynomial B[X], wherein the first input polynomial A[X] comprises N cm coefficients and the second input polynomial B[X] comprises N cn coefficients and said coefficients of the first and second input polynomials are of size N b bits, with Ncm, N cn and N b non-zero integers, said method comprising :
a) computing a polynomial result C[X] of a polynomial multiplication between said first input polynomial A[X] and said second input polynomial B[X] by :
- for the first input polynomial A[X], generating a concatenated integer A x as a concatenation of the coefficients of said first input polynomial, each coefficient being extended to a size N e with N e ≥ ⌈ log 2 Nc m ⌉ + 2 ∗ N b by inserting zeros as Most Significant Bits of said concatenated coefficients,
- obtaining each coefficient ci of the polynomial result by :
o for i an integer from 0 to N cn -1, wherein bi is the i-order coefficient of the second input polynomial B[X]:
▪ computing an intermediate value R i using said integer multiplier by multiplying said generated concatenated integer with said coefficient bi of the second input polynomial B[X] such that : Ri = R i -1 + A x ∗ bi where R -1 is equal to the value 0,
▪ storing the N e least significant bits of the intermediate value R i as the i th coefficient c i of the polynomial result C[X],
▪ applying a N e -bits right shift operation to the intermediate value Ri ,

o when i = N cn -1, for j an integer from N cn to Ncn+Ncm-2 :
▪ storing the N e least significant bits of the intermediate value R i as the j th coefficient cj of the polynomial result C[X],
▪ applying a N e -bits right shift operation to the intermediate value Ri,

b) performing said cryptographic algorithm using said determined polynomial result.

公开(公告)号：EP4258594A1

公开(公告)日：2023-10-11

申请号：EP22305467.7

申请日：2022-04-06

申请人： Thales Dis France SAS

发明人： LI, Xun ,  VIGILANT, David

IPC分类号： H04L9/30

摘要： The present invention relates to a method for performing a cryptographic algorithm, performed by a cryptographic device comprising a cryptographic coprocessor comprising an integer multiplier,
said cryptographic algorithm comprising a polynomial multiplication between a first input polynomial A[X] and a second input polynomial B[X], wherein the first input polynomial A[X] and the second input polynomial B[X] comprise Nc coefficients and said coefficients of the first and second input polynomials are of size Nb bits, with Nc and Nb non-zero integers, said method comprising :
a) computing (P1) a polynomial result of a polynomial multiplication between said first input polynomial A[X] and said second input polynomial B[X] by :
- for each input polynomial, generating (S11) a concatenated integer as a concatenation of the coefficients of said input polynomial, each coefficient being extended to a size Ne with N e ≥ ┌log 2 Nc ┐ + 2 * N b by inserting zeros as Most Significant Bits of said concatenated coefficients,
- computing (S12) using said integer multiplier a multiplication of said generated concatenated integers to obtain a multiplication result,
- determining (S13) from said multiplication result said polynomial result of a polynomial multiplication between said first input polynomial A[X] and said second input polynomial B[X],

b) performing (S21) said cryptographic algorithm using said determined polynomial result.