Patent ID: 8325928

Claim:
A computing device-implemented method for carrying out encryption using a key value for encrypting a plaintext value to define a cipher text, the encryption being defined using an encryption function, the method comprising: a processor executing the steps of: a) defining a masked encryption function by masking the encryption function using an encryption function mask value; b) defining a set of more than one split mask values, at least one, but not all, of the set of split mask values being defined with reference to the encryption function mask value and the remainder of the set of split mask values, such that when said set of split mask values are applied in masking steps, said at least one of the set of split mask values cancels with the remainder of the set of split mask values and said masking steps result in a masking as if said encryption function mask value was applied; c) generating a final mask value by masking the key value using masking steps that comprise masking by applying the set of split mask values to said key value, such that said final mask value is equivalent to masking said key value with said encryption function mask value; d) determining an input value by masking the plaintext value using masking steps that comprise masking by applying the final mask value; and e) applying the input value to the encryption function to provide a cipher text output.