leviathan
1.5 KiB
1.5 KiB
PSA (Peugeot/Citroën) Protocol
Rust module: src/protocols/psa.rs
Reference: REFERENCES/ProtoPirate/protocols/psa.c
Overview
PSA uses Manchester at 250/500 µs symbol (125/250 µs sub-symbol for preamble). 128 bits total: key1 (64) + validation (16) + key2/rest (48); decode uses key1 + 16-bit validation. TEA decrypt/encrypt with fixed key schedules; mode 0x23 adds an XOR layer. Two modes: seed 0x23 (TEA + XOR), seed 0xF3/0x36 (TEA, BF2 key schedule).
Timing
| Parameter | Value | Notes |
|---|---|---|
| Symbol short | 250 µs | ±100 µs |
| Symbol long | 500 µs | ±100 µs |
| Preamble | 125/250 µs sub-symbols | |
| Min bits | 128 |
Encoding
Manchester; preamble uses 125/250 µs; then 250/500 µs symbols. TEA encrypt; mode 0x23 adds XOR.
Frame Layout (128 bits)
- key1: 64 bits
- validation: 16 bits
- key2/rest: 48 bits
TEA decrypt key1 (and validation); mode 0x23: XOR with BF1 key schedule; mode 0x36: TEA with BF2 key schedule. Serial/button/counter extracted from decrypted key1.
Decoder Steps
- WaitEdge — Wait for edge/preamble.
- CountPattern — Count preamble pattern (125/250 µs).
- DecodeManchester — Manchester decode 128 bits; TEA decrypt; apply mode (0x23 XOR or 0x36); extract fields.
- End — End marker (e.g. 1000 µs); return decode.
Encoder
Supported; preamble, Manchester 128 bits, TEA (+ XOR for 0x23).
Frequencies
433.92 MHz.