What about power draw? Maybe that doesn't count as a side channel (I'm not a security guy). Afaik, CMOS transistors mostly draw power on switching state, so a normal adder adding 0+0 or 1+1 is visible in the power draw.
I googled a bit and found Sense Amplifier-Based Logic (SABL). Super interesting :^)
I googled a bit and found Sense Amplifier-Based Logic (SABL). Super interesting :^)