Identification of devices using physically unclonable functions

A method of generating a response to a physically unclonable function, said response being uniquely representative of the identity of a device having challengeable memory, the memory comprising an array of components each having an unstable state and at least two stable states, the method comprising applying an excitation signal to each of said components so as to drive each of said components into a respective one of said at least two stable states, and using resulting response data comprised of the combination of respective states of said components to generate a response pattern to said physically unclonable function, said response pattern being dependent on, and defined by, the physical characteristics of said memory, the method further comprising reading out said response pattern,

• wherein each of said components comprises a cross-coupled loop having an unstable state and at least two stable states,
• wherein each cross coupled loop comprises a pair of latches.

A method of generating a plurality of responses to respective physically unclonable functions, each response being uniquely representative of the identity of a respective device of a plurality of such devices of the same design, each device having challengeable memory, the method comprising applying the same one or more excitation signal to the memory of each of said plurality of devices, and reading the resulting response data from the memory of each of said plurality of devices,

• wherein each memory comprises an array of components each having an unstable state and at least two stable states, the method comprising applying said one or more excitation signals to each of said components so as to drive each of said components into a respective one of said at least two stable states, and reading resulting response data comprised of the combination of respective states of said components as a result of application of said one or more excitation signals thereto.