Module cipher 

AES-128-CBC encryption / decryption of SCS_17/SCS_18 DATA payloads.

Spec: Annex D.5

• DATA is always 0x80-padded (per super::pad::pad_data).
• The CBC ICV is the one’s complement of the last MAC received from the other device.
• Key is S-ENC.

Functions

complement_icv

Annex D.5 ICV: one’s complement of the last MAC from the other side.

decrypt_data

Decrypt a DATA payload and strip the 0x80 padding.

encrypt_data

Encrypt a DATA payload with AES-128-CBC, applying the always-0x80 padding rule. s_enc is the session encryption key, iv is the complemented MAC of the last frame received from the other side.