Detecting key corruption
AssigneeSTMicroelectronics (Research & Development) Limited
InventorMark Trimmer
Life of this patent
Estimating the term…
Abstract
Corruption in a key stored in a memory is detected by reading a key from a key memory and determining if detection bits of the key read from the key memory correspond to an expected value. The expected value is a value of the detection bits of the key when the key is written to the key memory.
Claims19
A method for determining corruption of a scrambled key, said scrambled key obtained by scrambling an initial key that includes a first set of data bits having key values and a second set of known bits having fixed values at fixed locations within the key, the known bits including a plurality of known bits each having a fixed value at a fixed location, the method comprising:
- reading the scrambled key from a memory;
- descrambling the scrambled key to recover a descrambled key having a third set of a data bits and a fourth set of detection bits;
- determining if the detection bits at corresponding fixed locations within the fourth set in the descrambled key have data values which match the fixed values of the known bits in the second set;
- and
- identifying the scrambled key as corrupt if the data value of any detection bit in the fourth set of the descrambled key does not match the fixed value of the known bit in the second set in the initial key.
An apparatus for determining corruption of a scrambled key stored in a memory, said scrambled key obtained by scrambling an initial key that includes a first set of data bits having key values and a second set of known bits having fixed values at fixed locations within the key, the known bits including a plurality of known bits each having a fixed value at a fixed location, the apparatus comprising:
- a processor configured to read the scrambled key from a memory and descramble the scrambled key to recover a descrambled key having a third set of a data bits and a fourth set of detection bits;
- checking hardware configured to determine if the detection bits at corresponding fixed locations within the fourth set in the descrambled key have data values which match the fixed values of the known bits in the second set and identify the scrambled key as corrupt if the data value of any detection bit in the fourth set of the descrambled key does not match the fixed value of the known bit in the second set in the initial key.
A non-transitory machine readable storage medium having executable instructions stored thereon for determining corruption of a scrambled key, said scrambled key obtained by scrambling an initial key that includes a first set of data bits having key values and a second set of known bits having fixed values at fixed locations within the key, the known bits including a plurality of known bits each having a fixed value at a fixed location, said executable instructions when performed by a processor comprises the steps of:
- reading the scrambled key from a memory;
- descrambling the scrambled key to recover a descrambled key having a third set of a data bits and a fourth set of detection bits;
- determining if the detection bits at corresponding fixed locations within the fourth set in the descrambled key have data values which match the fixed values of the known bits in the second set;
- and
- identifying the scrambled key as corrupt if the data value of any detection bit in the fourth set of the descrambled key does not match the fixed value of the known bit in the second set in the initial key.
A method for determining corruption of a scrambled key, said scrambled key obtained by scrambling an initial key that includes a first set of data bits having key values and a second set of known bits having fixed values at fixed locations within the key, the known bits including a plurality of known bit each having a fixed value at a fixed location, the method comprising:
- reading the scrambled key from a memory;
- descrambling the scrambled key to provide a descrambled key having a third set of a data bits and a fourth set of detection bits and recover the detection bits of the descrambled key at corresponding fixed locations;
- determining corruption if any of the detection bits at corresponding fixed locations within the fourth set in the descrambled key have a value that does not match the fixed value of the known bit in the second set in the initial key.
Dependencies are inferred from the claim text.