Patent ID: 7881465

Claim:
A circuit for calculating a logic combination of two encrypted input operands, comprising: a first input configured to receive a first dual-rail signal comprising data values of the first input in a calculation cycle and precharge values in a precharge cycle; a second input configured to receive a second dual-rail signal comprising data values of the second input in the calculation cycle and precharge values in the precharge cycle; a third input configured to receive a dual-rail encryption signal comprising encryption values in the calculation cycle and precharge values in the precharge cycle; an output configured to output a dual-rail result signal comprising encrypted result values in the calculation cycle and precharge values in the precharge cycle; wherein the data values of the first and second dual-rail signals and the encrypted result values of the dual-rail result signal are encrypted with the encryption values of the dual-rail encryption signal according to an encryption rule; a logic circuit configured to determine the encrypted result values according to the logic combination from the data values of the first input and of the second input and the encryption values, and to output the encrypted result values at the output in the calculation cycle; and a precharge circuit configured to already impress precharge values in the output, when precharge values are sensed at a single input, or formed to start impressing the precharge values only when the first dual-rail signal and the second dual-rail signal comprise data values and the dual-rail encryption signal comprises encryption values.