Datum reading error detection method

A method for detecting an error in the reading of a data item, comprising:

• a) storing a first copy of the data item in a first area of an electronic memory and storing a second copy of the data item in a second area of an electronic memory, in response to a request to read the data item:
• b) reading a value of the first copy and a value of the second copy of the data item in the first and second areas, respectively,
• c) comparing the read values of the first and second copies of the data item,
• d) if the read values of the first and second copies are identical, then no error in the reading of this data item is detected,
• e) if the read values of the first and second copies are different, then the preceding steps b) and c) are repeated, then
• f) if the values read in step e) are identical, then an error in the reading of the data item is detected and, otherwise, no error in the reading of this data item is detected.

A method for protecting a security processor from a reading attack, the security processor executing a routine of enciphering or deciphering an information item using a confidential data item stored in first and second memory areas of this security processor, comprising:

• detecting an error in the reading of the confidential data item, comprising,
• a) storing a first copy of the data item in a first area of an electronic memory and storing a second copy of the data item in a second area of an electronic memory, in response to a request to read the data item:
• b) reading a value of the first copy and a value of the second copy of the data item in the first and second areas, respectively,
• c) comparing the read values of the first and second copies of the data item,
• d) if the read values of the first and second copies are identical, then no error in the reading of this data item is detected,
• e) if the read values of the first and second copies are different, then the preceding steps b) and c) are repeated, then
• f) if the values read in step e) are identical, then an error in the reading of the data item is detected and, otherwise, no error in the reading of this data item is detected,
• wherein, if no error in the reading of the confidential data item is detected, the security processor continues with the enciphering or deciphering of the information item using the read confidential data item, otherwise
• in response to the detection of a reading error, the security processor automatically triggers a countermeasure limiting the enciphering or deciphering of the information item using the read confidential data item, with respect to the case where no error in the reading of this confidential data item is detected.

Software stored in a security processor for protecting the security processor from a reading attack, the security processor executing a routine of enciphering or deciphering an information item using a confidential data item stored in first and second memory areas of the security processor, the software comprising instructions for causing the security processor to

• detect an error in the reading of the confidential data item, comprising,
• a) storing a first copy of the data item in a first area of an electronic memory and storing a second copy of the data item in a second area of an electronic memory, in response to a request to read the data item:
• b) reading a value of the first copy and a value of the second copy of the data item in the first and second areas, respectively,
• c) comparing the read values of the first and second copies of the data item,
• d) if the read values of the first and second copies are identical, then no error in the reading of this data item is detected,
• e) if the read values of the first and second copies are different, then the preceding steps b) and c) are repeated, then
• f) if the values read in step e) are identical, then an error in the reading of the data item is detected and, otherwise, no error in the reading of this data item is detected,
• wherein, if no error in the reading of the confidential data item is detected, the security processor continues with the enciphering or deciphering of the information item using the read confidential data item, otherwise
• in response to the detection of a reading error, the security processor automatically triggers a countermeasure limiting the enciphering or deciphering of the information item using the read confidential data item, with respect to the case where no error in the reading of this confidential data item is detected.

A security processor, comprising:

• first and second areas of an electronic memory,
• an electronic computer programmed to:
• a) store a first copy of the data item in the first area and store a second copy of the data item in the second area, in response to a request to read the data item:
• b) read the values of the first and second copies of the data item in the first and second areas respectively,
• c) compare the read values of the first and second copies of the data item, and
• d) if the read values of the first and second copies are identical, then detect no error in the reading of this data item,
• e) if the read values of the first and second copies are different, repeat the preceding steps b) and c), then
• f) if the values read in the step e) are identical, then detect an error in the reading of this data item and, otherwise, indicate no reading error.