This is a 2D top-down reading of the same fleet-encryption model as the 3D lab: sensor devices sit on a ring around a central gateway, each packet pays a radio-transmit energy cost plus (if encrypted) a cipher energy cost, and the session key rotates on a timer.
E_tx = bytes/pkt · 0.5 µJ/byte (radio TX, all modes)
E_crypto= payload · c_cipher µJ/byte (0 if unencrypted)
E_rot = 150 µJ / device, once per rotation interval T_rot
E_total = N_dev·rate·(E_tx+E_crypto) + N_dev·150/T_rot [µJ/s]
Cipher energy constants (µJ/byte of payload, typical Cortex-M0 without AES hardware) and per-packet header/tag overhead:
None : c=0.00 overhead=0 B (plaintext — no confidentiality)
AES-128-CCM: c=0.30 overhead=13 B key=128 bit
AES-256-GCM: c=0.45 overhead=16 B key=256 bit
ChaCha20-Poly1305: c=0.20 overhead=16 B key=256 bit (fast in pure software)
Battery life is a fixed 3000 mAh / 3.7 V cell's energy divided by one device's share of E_total. A 3000 mAh cell at 3.7 V holds 3000·3.7 = 11,100 mWh, and since 1 mWh = 1 mW acting for 3600 s = 3600 mJ, that is 11,100 × 3600 ≈ 4.0×10⁷ mJ of usable energy. Brute-force time uses log-scale arithmetic (never raising 2 to a 256th power directly) to avoid overflow: years ≈ 10^[(bits−1)·log₁₀2 − log₁₀(ops/s · seconds/year)].
- Cipher buttons — swap the running algorithm; packet color and every readout update instantly.
- Devices / Packet rate — scale the fleet's traffic; more traffic means more crypto energy but also a shorter real exposure window per bit sent.
- Key-rotation interval — how often a fresh session key is negotiated. Shorter intervals shrink the practical "if this key leaks, how long is the attacker inside" window at the cost of handshake energy; the theoretical brute-force time is astronomically larger regardless, so rotation — not raw key length — is what actually bounds real-world exposure.
- Drag to pan, scroll to zoom — the ring redraws at any scale; the physics readouts never depend on the view.
Plaintext ("None") has no key at all, so its exposure window is not bounded by rotation — anyone on the network path reads every packet immediately.