Patent ID: 8848477

Claim:
An electric physical unclonable function (PUF) ( 100 , 200 ) comprising a semiconductor memory element ( 110 ) connectable to a PUF control means ( 120 ) for reading content from the memory element and for deriving at least in part from said content a digital identifier, the memory element being of a type that is configurable into at least two different stable states, the stable states representing the content of the memory element, the memory element comprising a power input for electrically powering the memory element and bringing the memory element into a powered-up state, and a control input ( 112 ) for receiving one or more control signals, the control signals configuring the memory element into a selected one of the at least two different stable states, the memory element being configured to settle into one of the at least two different stable states upon power-up, the particular stable state into which the memory element settles being dependent at least in part upon the at least partially random physical characteristics of the memory element, wherein the particular stable state into which the memory element settles upon power-up is also dependent upon the control input receiving a control signal, the electric physical unclonable function further comprises shielding means ( 142 , 144 ) for shielding, during a time period including the power-up of the memory element and lasting at least until the settling of the memory element, the control input from receiving control signals upon which the particular stable state into which the memory element settles is dependent, by connecting the control input with a reference voltage line.