canbus: solve IDS-CAN command-auth cipher; add reference implementations
The CAN write gate (page-42/43 challenge/response) is a 32-round TEA/XTEA-family Feistel keyed by a per-session 32-bit key; REMOTE_CONTROL = 0xB16B00B5. Verified 51/51 against captured challenge/response pairs across nodes 2A/61/75/F8 (one global key, not per-node), so the CAN path can now actuate, not just sense. - ids_can_auth.py Python reference + self-test (51/51) - esphome/ids_can_auth.h C++ port for the ESP32 node (host-tested 8/8) - sniff/analyze_auth.py structural analysis (rules out affine; confirms keyed cipher) - sniff/auth-pairs-multinode-2026-06-11.txt +9 pairs across 4 nodes - README document the cipher, session keys, unlock sequence Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Claude Fable 5
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#!/usr/bin/env python3
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"""Structural analysis of the IDS-CAN command-auth challenge->response map.
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Black-box: decide what the captured (challenge, response) pairs can and cannot
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tell us about f, where response = f(challenge). Pure stdlib.
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Usage: ./analyze_auth.py [pairfile ...]
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Default: loads 2A-auth-pairs.txt + auth-pairs-multinode-2026-06-11.txt (51 pairs).
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Pair-file format: lines of "<challenge_hex> <response_hex>", optionally prefixed
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with a node label ("<node> <challenge> <response>"); '#' comments ignored.
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"""
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import os
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import sys
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HERE = os.path.dirname(os.path.abspath(__file__))
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DEFAULTS = [
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os.path.join(HERE, "2A-auth-pairs.txt"),
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os.path.join(HERE, "auth-pairs-multinode-2026-06-11.txt"),
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]
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def load(paths):
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pairs = []
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for path in paths:
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with open(path) as f:
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for line in f:
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line = line.strip()
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if not line or line.startswith("#"):
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continue
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tok = line.split()
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c, r = tok[-2], tok[-1] # tolerate optional node label
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pairs.append((int(c, 16), int(r, 16)))
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return pairs
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def reduce_vec(iv, ov, basis):
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for piv, bi, bo in basis:
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if (iv >> piv) & 1:
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iv ^= bi
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ov ^= bo
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return iv, ov
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def main():
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paths = sys.argv[1:] or DEFAULTS
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pairs = load(paths)
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n = len(pairs)
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print(f"loaded {n} pairs from {', '.join(os.path.basename(p) for p in paths)}\n")
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# determinism is only testable if a challenge recurs (else the check is vacuous)
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chals = [c for c, _ in pairs]
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repeats = len(chals) - len(set(chals))
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print(f"[determinism] {len(set(chals))} distinct challenges, {repeats} repeated "
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f"-> {'testable' if repeats else 'NOT testable (all distinct; statelessness assumed)'}")
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# TEST 1: GF(2)-affine. f(x)=M.x^k => f(Ci)^f(Cj)=M.(Ci^Cj) (constant cancels).
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# Reduce input-diffs against a growing basis; an input-diff that collapses to 0
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# while its output-diff does not => NOT affine. Full rank + consistent => solved.
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C0, R0 = pairs[0]
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basis, contradiction = [], None
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for c, r in pairs[1:]:
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iv, ov = reduce_vec(c ^ C0, r ^ R0, basis)
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if iv == 0:
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if ov != 0 and contradiction is None:
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contradiction = ov
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else:
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basis.append((iv.bit_length() - 1, iv, ov))
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rank = len(basis)
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print(f"\n[TEST 1: GF(2)-affine] input-difference rank = {rank}/32")
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if contradiction is not None:
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print(" -> NOT GF(2)-affine (linear fit contradicted despite full-rank data;"
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" obstacle is structure, not sample count)")
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elif rank == 32:
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applyM = lambda x: reduce_vec(x, 0, basis)[1]
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k = R0 ^ applyM(C0)
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bad = sum((applyM(c) ^ k) != r for c, r in pairs)
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print(f" -> AFFINE & SOLVED: k={k:#010x}, mismatches={bad}/{n}")
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else:
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print(f" -> consistent w/ affine but underdetermined ({rank}/32); need more pairs")
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# TEST 2: affine over Z/2^32. R=a*C+b mod 2^32; derive a from one odd diff, verify.
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MOD = 1 << 32
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a = None
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for c, r in pairs[1:]:
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dc = (c - C0) % MOD
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if dc & 1:
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inv = 1
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for _ in range(6):
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inv = (inv * (2 - dc * inv)) % MOD
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a = ((r - R0) * inv) % MOD
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break
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print("\n[TEST 2: affine over Z/2^32 R=a*C+b]")
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if a is None:
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print(" -> no odd input-difference; skipped")
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else:
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b = (R0 - a * C0) % MOD
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bad = sum((a * c + b) % MOD != r for c, r in pairs)
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print(f" a={a:#010x} b={b:#010x} -> {bad}/{n} miss"
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f" -> {'SOLVED' if bad == 0 else 'not a ring-affine map'}")
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# TEST 3: byte locality. Is out-byte p a pure function of a single in-byte q?
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byte = lambda v, i: (v >> (8 * (3 - i))) & 0xFF
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local = []
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for p in range(4):
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for q in range(4):
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groups = {}
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ok = True
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for c, r in pairs:
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key = byte(c, q)
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if key in groups and groups[key] != byte(r, p):
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ok = False
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break
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groups[key] = byte(r, p)
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if ok and any(sum(byte(c, q) == k for c, _ in pairs) > 1 for k in groups):
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local.append((p, q))
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print("\n[TEST 3: byte locality]",
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"out-byte/in-byte dependencies:" if local else
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"-> no out-byte is a function of any single in-byte (full diffusion)")
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for p, q in local:
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print(f" out-byte {p} may depend only on in-byte {q} (check w/ more data)")
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# TEST 4: per-bit balance (informative, not decisive at this sample size)
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ones_in = [sum((c >> b) & 1 for c, _ in pairs) for b in range(32)]
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ones_out = [sum((r >> b) & 1 for _, r in pairs) for b in range(32)]
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print(f"\n[TEST 4: per-bit balance] (ideal 0.5) "
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f"challenge {min(ones_in)/n:.2f}-{max(ones_in)/n:.2f}, "
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f"response {min(ones_out)/n:.2f}-{max(ones_out)/n:.2f}")
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print("\nVERDICT: keyed nonlinear cipher (TEA/XTEA-family), not recoverable from "
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"random known-plaintext pairs at any feasible count. SOLVED 2026-06-12 "
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"(REMOTE_CONTROL session key 0xB16B00B5), verified 51/51 here — see "
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"../ids_can_auth.py.")
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if __name__ == "__main__":
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main()
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@@ -0,0 +1,34 @@
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# Lippert IDS-CAN command-auth challenge/response pairs — MULTI-NODE
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# Captured 2026-06-11, app-driven (phone app issued on/off/move commands).
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# Source log: app-commands-2026-06-11_230059.log (node 2A bulk set lives in 2A-auth-pairs.txt).
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#
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# Exchange (controller node 01 <-> module node), all 29-bit extended frames:
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# id = (src<<18) | (dir<<16) | (dest<<8) | page dir: 0 = 01->node, 1 = node->01
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# arm 01->node page42 DLC2 "00 04"
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# challenge node->01 page42 DLC6 "00 04 <CC CC CC CC>"
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# response 01->node page43 DLC6 "00 04 <RR RR RR RR>"
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# ack node->01 page43 DLC2 "00 04"
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# format below: <challenge_hex> <response_hex> (the 4-byte payload tails)
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#
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# Confirmed: the SAME handshake gates every node tested — switched loads AND the
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# awning (movement class). 51 pairs total across 4 nodes; response = f(challenge)
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# is nonlinear (not GF(2)-affine, not Z/2^32-affine, full byte diffusion).
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# node 61 — water pump (type 0x1E switched load)
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61 FE06BF48 58AEA9BE
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61 D57BE45A A1FB45E1
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# node 75 — awning (type 0x21 H-bridge/movement) — full nonce gate, same as loads
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75 A009E94C 5ADC2B0D
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75 5F8A7647 4CA89152
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75 6A873757 02592CF2
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# node F8 — interior lights (type 0x1E switched load)
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F8 F7740A20 BDB16954
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F8 EDC9281A 87EFB3EF
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# node 2A — exterior lights (type 0x1E) — 2 extra pairs from this session;
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# 42 more in 2A-auth-pairs.txt (extlight-authpairs-*.log). 21CA0C06 is the pair
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# the README used to rule out the BLE TEA key.
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2A 21CA0C06 CC18366B
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2A 4FC2C0FF 2B47861E
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