Reusing memory arrays for physically unclonable function (PUF) generation

A system comprising:

• a boot ROM including an array of bit cells programmed with boot code, wherein existence of a transistor in a bit cell indicates a first logic state of a corresponding stored bit of the boot code and lack of the transistor in the bit cell indicates a second logic state of the corresponding stored bit of the boot code, wherein the array of bit cells is arranged in rows and columns, wherein each row comprises a corresponding word line and each column comprises a corresponding bit line;
• differential PUF bits embedded in the array of the boot ROM, each differential PUF bit including a first bit cell of the array of bit cells programmed with boot code and a second bit cell of the array of bit cells programmed with boot code;
• a first set of sense-amplifiers coupled to the bit lines of the array and configured to output from the array a set of data bits of the boot code stored at a selected word line and selected bit lines;
• a second set of sense-amplifiers coupled to the bit lines of the array and configured to output a set of differential output bits, each differential output bit based on a voltage or current differential between two bit lines of the selected bit lines corresponding to the first and second bit cells of a corresponding differential PUF bit along the selected word line;
• a potential PUF bit generator configured to output a set of potential PUF bits from the array based on the set of data bits of the user data from the first set of sense-amplifiers and the set of differential output bits from the second set of sense-amplifiers;
• and
• a filter circuit configured to receive the set of potential PUF bits from the potential PUF bit generator to identify a subset of the potential PUF bits as valid PUF bits thereby filtering out any invalid PUF bits from the set of potential PUF bits.