[otbn/sca] add config option to disable mask

Signed-off-by: Michael Tempelmeier <[email protected]>

cw/capture.py

@@ -1082,10 +1082,15 @@ def capture_otbn_vertical(ot, ktp, fw_bin, pll_frequency, capture_cfg):
 
  ot.scope.adc.offset = capture_cfg["offset"]
 
- # Generate a new random mask for each trace.
- mask = ktp.next_text()
- tqdm.write(f'mask = {mask.hex()}')
+ if capture_cfg["masks_off"] is True:
+ # Use a constant mask for each trace
+ mask = bytearray(capture_cfg["plain_text_len_bytes"]) # all zeros
+ else:
+ # Generate a new random mask for each trace.
+ mask = ktp.next_text()
+
  tqdm.write("Starting new trace....")
+ tqdm.write(f'mask = {mask.hex()}')
 
  if sample_fixed:
  # Use the fixed seed.

cw/capture_otbn_vertical.yaml

@@ -13,6 +13,7 @@ capture:
  use_fixed_key_iter: False # See https://github.com/lowRISC/ot-sca/issues/116
  key_len_bytes: 40
  plain_text_len_bytes: 40
+ masks_off: true
  # Output length (most likely unused).
  output_len_bytes: 40
  # Samples per trace