[aes] Fix aes_fvsr_key_batch on CW305

Previously, the commands for seeding the batch PRNG and seeting the fixed key seemed to interfere resulting in the target implemented on the CW305 getting completely out of sync. Signed-off-by: Pirmin Vogel <[email protected]>
lowRISC · Apr 17, 2023 · 6b41a34 · 6b41a34
1 parent 39b01b7
commit 6b41a34
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/cw/capture.py b/cw/capture.py
@@ -449,6 +449,10 @@ def capture_aes_fvsr_key_batch(ot, ktp, capture_cfg, scope_type, gen_ciphertexts
     # Seed the target's PRNG
     ot.target.simpleserial_write("s", capture_cfg["batch_prng_seed"].to_bytes(4, "little"))
 
+    # Set and transfer the fixed key.
+    # Without the sleep statement, the CW305 seems to fail to configure the batch PRNG
+    # seed and/or the fixed key and then gets completely out of sync.
+    time.sleep(0.5)
     key_fixed = bytearray([0x81, 0x1E, 0x37, 0x31, 0xB0, 0x12, 0x0A, 0x78,
                            0x42, 0x78, 0x1E, 0x22, 0xB2, 0x5C, 0xDD, 0xF9])
     tqdm.write(f'Fixed key: {binascii.b2a_hex(bytes(key_fixed))}')