trace is correlatable with the target bit on the data bus driver the correlation can then be used to determine the secret key the present invention prevents usage of side channel information by dpa attackers by randomly toggling the polarity of the target bit at the data bus driver while maintaining the equal probability of having a u2018 0 u2019 or u2018 1 u2019 values in other words the power traces no longer statistically correlate with the secret key thus side channel information cannot be used to determine the keys being used by the cryptographic system specifically with reference to dpa the result is that within each group of messages having the same target bit values computed from the selection function with correctly guessed key k s the corresponding power traces will not be always u2018 0 u2019 or u2018 1 u2019 the chance of having a u2018 0 u2019 or u2018 1 u2019 at the target bit will be approximately at 0 5 due to the randomization of polarity thus the selection function d is effectively un correlatable to the actual power trace measurement the selection function d has thus been deprived of a way of predicting the power consumption of the actual target bit in the case of.