Reliable physical unclonable function for device authentication
View Patent ↗A method of manufacturing a secure device having a physical unclonable function includes embedding a phase change memory in the secure device, where the phase change memory includes a plurality of cells, and setting the phase change memory in a manner that results in a phase variation over the plurality of cells, wherein the phase variation is the physical unclonable function. A method for retrieving a cryptographic key from an integrated circuit, wherein the cryptographic key is stored in the integrated circuit, includes measuring a property of a phase change memory embedded in the integrated circuit, wherein the phase change memory includes a plurality of cells and the property is a function of a phase variation over the plurality of cells, deriving a signature from the property, and deriving the cryptographic key from the signature.
1. A method of manufacturing a secure device having a physical unclonable function, the method comprising:
embedding a phase change memory in the secure device, the phase change memory comprising a plurality of cells; and
setting the phase change memory in a manner that results in a non-uniform phase being exhibited over the plurality of cells, wherein the non-uniform phase is manifested by at least two of the plurality of cells being set to different phases, wherein each of the different phases is one of fully amorphous, fully crystalline, or between fully amorphous and fully crystalline, and wherein the non-uniform phase comprises the physical unclonable function; measuring a property of the phase change memory for deriving a signature having one or more physical unclonable function values; and deriving a binary key from the signature, wherein the binary key is derived by applying a threshold to the one or more physical unclonable function values for conversion into a binary code.
2. The method of claim 1 , wherein the phase change memory comprises chalcogenide glass.
3. The method of claim 1 , wherein the setting comprises:
performing a laser anneal on the phase change memory.
4. The method of claim 1 , wherein the setting comprises:
applying a programming pulse to the phase change memory.
5. The method of claim 1 , wherein the property comprises collective resistivity values of individual cells of the plurality of cells.
6. The method of claim 1 , wherein the property of the semiconducting material is measured by a measurement circuit.
7. The method of claim 6 , further comprising:
deriving a binary key from the signature, wherein the binary key is derived by applying a threshold to the one or more physical unclonable function values, wherein the deriving the binary key from the signature is performed by the measurement circuit.
8. The method of claim 1 , wherein the non-uniform phase comprises a random phase variation over the plurality of cells.
9. A method for retrieving a cryptographic key from an integrated circuit, wherein the cryptographic key is stored in the integrated circuit, the method comprising:
measuring a property of a phase change memory embedded in the integrated circuit, wherein the phase change memory comprises a plurality of cells and the property is a function of a non-uniform phase exhibited over the plurality of cells, wherein the non-uniform phase is manifested by at least two of the plurality of cells being set to different phases, wherein each of the different phases is one of fully amorphous, fully crystalline, or between fully amorphous and fully crystalline;
deriving a signature from the property, wherein the signature comprises at least one measured value of the property; and
deriving the cryptographic key from the signature by applying a threshold to the at least one measured value.
10. The method of claim 9 , wherein the phase change memory comprises chalcogenide glass.
11. The method of claim 9 , wherein the property comprises a resistivity.
12. The method of claim 9 , wherein the non-uniform phase comprises a random phase variation over the plurality of cells.
13. The method of claim 1 , wherein the setting comprises applying a stimulus to the phase change memory as a whole, including all of the plurality of cells, and wherein the stimulus induces a random distribution of the different phases in the plurality of cells.
14. The method of claim 1 , wherein the random distribution is unique to the secure device relative at least to other secure devices manufactured in a common batch with the secure device.
15. The method of claim 1 , wherein the embedding comprises deploying the phase change memory in a backend of the secure device.
16. The method of claim 1 , further comprising:
placing a measurement circuit in the backend of the secure device, in a separate layer from the phase change memory, wherein the measurement circuit is configured to measure a property of the phase change memory.