I tried to run the CW305_ECC demo project.
I found that the power traces of the example ecc code on CW305 had no obviously difference between two different keys.
Here I showed the power traces with two keys (the power trace is sample with scope.adc.decimate = 20):
red: k = 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
blue: k = 0x8000000000000000000000000000000000000000000000000000000000000000
Then I went to check the verilog code of ecc in the demo project.
It seemed that the scalar multiplication is implemented by double-and-add-always method.
Is my assumption correct?