There is disclosed a method of generating a digital signature of a message m. A signature component s of the digital signature is calculated by first masking the long-term private key d using a single additive operation to combine the key d with a first value. The masked value is then multiplied by a second value to obtain component s. The first value is calculated using the message m and another component of the digital signature, and the second value is derived using the inverse of a component of the first value. In this way, the signature component s is generated using a method that counters the effectiveness of side channel attacks, such as differential side channel analysis, by avoiding a direct multiplication using long-term private key d.