Transistor based PUF apparatus
View Patent ↗The present disclosure relates to a PUF apparatus and method for generating a persistent, random number. The generated number is random in that each particular instance of PUF apparatus should generate a randomly different number to all other instances of PUF apparatus, and is persistent in that each particular instance of the PUF apparatus should repeatedly generate the same number, within acceptable error correction tolerances. The persistent, random number is determined by selecting one or more PUF cells, each comprising a matched pair of transistors that are of identical design, and comparing an on-state characteristic of the pair (e.g., turn-on threshold voltage or gate-source voltage). The difference in on-state characteristic of each selected pair of transistors is caused by random manufacturing differences between the transistors. This causes the randomness between each different instance of PUF apparatus, and should be relatively stable over time to provide persistence of the generated number.
1. A Physically Unclonable Function, PUF, apparatus comprising:
an array of individually selectable PUF cells, wherein each PUF cell of the array comprises a plurality of matched devices;
selection circuitry configured to select first and second PUF cells of the array of individually selectable PUF cells; and
determination circuitry configured to read out in parallel device difference values from
the plurality of matched devices of the first and second PUF cells of the array of individually selectable PUF cells.
2. The PUF apparatus of claim 1 , wherein the array of individually selectable PUF cells comprises a row of PUF cells and a plurality of columns of PUF cells, and wherein the first and second PUF cells form part of the row of PUF cells.
3. The PUF apparatus of claim 2 , further comprising a plurality of chop circuits, wherein a first chop circuit of the plurality of chop circuits is shared by PUF cells in a first column of the plurality of columns of PUF cells.
4. The PUF apparatus of claim 2 , further comprising source circuitry configured to apply a common current source signal to PUF cells within a column of PUF cells of the array of individually selectable PUF cells.
5. The PUF apparatus of claim 2 , wherein PUF cells in the row of PUF cells share an output from the selection circuitry.
6. The PUF apparatus of claim 2 , further comprising a plurality of ADCs, wherein a first ADC of the plurality of ADCs is shared by PUF cells in a respective column of the plurality of columns of PUF cells.
7. The PUF apparatus of claim 6 , wherein the plurality of ADCs share a ramp signal.
8. The PUF apparatus of claim 1 , wherein the matched devices are matched transistors.
9. The PUF apparatus of claim 8 , wherein the device difference values comprise transistor difference values, based on a comparison of an on-state characteristic of the matched transistors.
10. A Physically Unclonable Function, PUF, apparatus comprising:
rows and columns of PUF cells, wherein the PUF cells of a first row of the rows each comprises a plurality of matched devices;
selection circuitry configured to select the PUF cells of the first row; and
determination circuitry configured to read out in parallel device difference values from the PUF cells of the first row of PUF cells.
11. The PUF apparatus of claim 10 , wherein the matched devices are matched transistors.
12. The PUF apparatus of claim 10 , wherein the determination circuitry comprises a respective analog-to-digital converter (ADC) configured to process read out signals from PUF cells of the first row in parallel.
13. The PUF apparatus of claim 10 , further comprising a plurality of chop circuits, wherein each chop circuit of the plurality of chop circuits is shared by PUF cells in a respective column of the columns of PUF cells.
14. The PUF apparatus of claim 10 , further comprising a plurality of ADCs, wherein each ADC of the plurality of ADCs is shared by PUF cells in a column of the columns of PUF cells.
15. The PUF apparatus of claim 14 , wherein the plurality of ADCs share at least one resource, comprising at least one of a ramp signal or a counter value.
16. The PUF apparatus of claim 10 , wherein PUF cells in the first row of PUF cells share an output from the selection circuitry.
17. A Physically Unclonable Function, PUF, apparatus comprising:
a first PUF cell comprising a pair of matched transistors;
a second PUF cell comprising a pair of matched transistors;
first source circuitry configured to apply a first source signal to the pair of matched transistors of the first PUF cell;
second source circuitry configured to apply a second source signal to the pair of matched transistors of the second PUF cell; and
determination circuitry configured to read out transistor difference values from the first PUF cell and second PUF cell in parallel.
18. The PUF apparatus of claim 17 , wherein the determination circuitry comprises first and second analog-to-digital converters (ADCs) configured to process read out signals from the first PUF cell and second PUF cell, respectively.
19. The PUF apparatus of claim 18 , wherein the first and second ADCs share a ramp signal.
20. The PUF apparatus of claim 17 , further comprising a plurality of chop circuits coupled to the first PUF cell and second PUF cell, respectively.