Security countermeasures for power analysis attacks
View Patent ↗A countermeasure for differential power analysis attacks on computing devices. The countermeasure includes the definition of a set of split mask values. The split mask values are applied to a key value used in conjunction with a masked table defined with reference to a table mask value. The set of n split mask values are defined by randomly generating n−1 split mask values and defining an nth split mask value by exclusive or'ing the table mask value with the n−1 randomly generated split mask values.
1. A computing device implemented method for executing a split-mask, masking countermeasure for improving the resistance, to power analysis attacks, of a processing unit of the computing device performing a defined cryptographic function using a key, the method comprising the processing unit executing the following steps:
obtaining the key and a random key mask value r;
obtaining a set of n random input values m in 1, . . . m in n;
defining a masked function by masking the defined cryptographic function with the value m in 1^. . . ^m in n;
masking the key with the random key mask value r to define the value mkey;
obtaining a set of random split mask values m1, . . . mn−1;
defining a split mask value mn to be r^m in 1^. . . ^m in n^m1^. . . ^mn−1; and
using the values m1, . . . , mn and mkey to define input for the masked function.
2. The method of claim 1 in which the encryption function is a table look-up.
3. The method of claims 1 or 2 in which masking is a bitwise exclusive or operation carried out on binary values.
4. A computing device implemented method for executing a split-mask, masking countermeasure for improving the resistance, to power analysis attacks, of a processing unit of the computing device performing a cryptographic function using a key to encrypt a plaintext value using a look up on a defined look-up table, the method comprising the processing unit executing the following steps:
obtaining the key and a random key mask value r;
defining a value mkey by masking the key with the random key mask value r;
obtaining a set of n random input values m in 1, . . . m in n;
defining a masked table by masking the defined look-up table with the value m in 1^. . . ^m in n;
obtaining a set of split mask values comprising random values m1, . . . mn−1;
defining a split mask value mn to be r^m in 1^. . . ^m in n^m1^. . . ^mn−1; and
masking the plaintext with the split mask values m1, . . . , mn and mkey to define input for the
masked table, the masked table to be used in place of the defined look-up table in the cryptographic operation.
5. The method of claim 4 in which masking is a bitwise exclusive or operation carried out on binary values.
6. A computing device program product for improving the resistance, to power analysis attacks, of a processing unit using a key to perform a defined cryptographic function, the computing device program product comprising a computer usable storage medium having computer readable program code means stored in said storage medium, and comprising
program code means for obtaining the key and a random key mask value r,
program code means for obtaining a set of n random input values m in 1, m in n,
program code means for defining a masked function by masking the defined cryptographic function with the value m in 1^. . . ^m in n,
program code means for masking the key with the random key mask value r to define the value mkey,
program code means for obtaining a set of random split mask values m1, . . . mn−1,
program code means for defining a split mask value mn to be r^m in 1^m in n^m1^. . . ^mn−1, and
program code means for using the values m1, . . . , mn and mkey to define input for the masked function.
7. The computing device program product of claim 6 in which the encryption function is a table look-up.
8. The computing device program product of claims 6 or 7 in which masking is a bitwise exclusive or operation carried out on binary values.
9. A computing device program product for improving the resistance, to power analysis attacks, of a processing unit performing a cryptographic function using a key to encrypt a plaintext value using a look up on a table, the computing device program product comprising a computer usable storage medium having computer readable program code means stored in said storage medium, and comprising
program code means for obtaining the key and a random key mask value r,
program code means for obtaining a set of n random input values m in 1, . . . m in n,
program code means for defining a masked table by masking the defined look-up table with the value m in 1^. . . ^m in n,
program code means for masking the key with the random key mask value r to define the value mkey,
program code means for obtaining a set of random split mask values m1, . . . mn−1,
program code means for defining a split mask value mn to be r^m in 1^. . . ^m in n^m1^. . . ^mn−1, and
program code means for masking the plaintext with the values m1, . . . , mn and mkey to define input for the masked table.
10. The computing device program product of claim 9 in which masking is a bitwise exclusive or operation carried out on binary values.