khensu shell
Your phone becomes part of the network
One shell for iPhone 18 Pro and iPhone 18 Pro Max, coming to iPhone 18 when it arrives. Ceramic-coated titanium in your iPhone’s colour, or solid brass. It turns the phone into a node with its own battery, finishes level with the lenses so your iPhone is no thicker at its thickest point, and leaves the iPhone’s own USB-C port open.
Specifications
| Item | Specification |
|---|---|
| Fits | iPhone 18 Pro and iPhone 18 Pro Max. Coming to iPhone 18 when it arrives. |
| Thickness | 4.2 mm on the back, level with the lens tops: +0 mm at the iPhone’s thickest point. A flat back, with only the lenses showing. |
| Footprint | 71.1 × 149.2 mm, inset 0.4 mm from the phone’s outline and following its edge curve, so it never overhangs |
| Shell | CNC-machined Grade 5 titanium (Ti-6Al-4V), with a ceramic finish: a plasma electrolytic oxide layer grown from the titanium itself, sealed with a colour-matched ceramic topcoat in Burgundy, Glacier, Silver or Black. Or bare solid brass (C26000), which darkens to a natural patina. |
| Weight | About 93 g in titanium, 136 g in brass |
| Battery | 6.2 Wh, about 5 hours as a node on its own |
| USB-C | The shell has its own USB-C port in its bottom edge, above the iPhone’s. The iPhone’s port stays open: charge both at once, from two cables or one dual USB-C cable, and keep using the iPhone’s port for drives, displays, audio and CarPlay. |
| Attachment | MagSafe-compatible magnet ring and a 0.5 mm micro-suction urethane layer that is also the shock isolator |
| Antennas | A band in the bottom edge, so nearby nodes reach each other directly where there’s no internet |
| Camera | Clears every lens, flash and sensor, outside each one’s field of view |
Figures for iPhone 18 Pro, from the current CAD model on placeholder geometry, until Apple’s accessory drawings are available; production figures may change. iPhone, MagSafe and CarPlay are trademarks of Apple Inc.
Inside
| Part | Hardware |
|---|---|
| Node computer | NXP i.MX 93 (2× Arm Cortex-A55, Cortex-M33, EdgeLock Secure Enclave), 2 GB LPDDR4X, 32 GB eMMC |
| Network guard | STMicroelectronics STM32U5 (Arm Cortex-M33 with TrustZone), running open Rust firmware with post-quantum secure boot. It owns every radio. |
| Mesh radio | Wi-Fi HaLow (802.11ah), Morse Micro MM6108 |
| Wi-Fi and Bluetooth | NXP IW612: Wi-Fi 6, Bluetooth LE, 802.15.4 |
| Battery | Single-cell lithium-ion pouch, 3.85 V, about 1,610 mAh (6.2 Wh), shaped to the shell, with protection and temperature sensing. Certified to IEC 62133-2 and UN 38.3. |
| USB-C Power Delivery | Texas Instruments TPS25750 controller |
| Charger | Texas Instruments BQ25895, single cell, with power path |
| Fuel gauge | Texas Instruments BQ27427 |
| Shock layer | Microcellular urethane, Rogers PORON XRD class, 0.5 mm, with a micro-suction face |
| Board | 34 × 14 × 1.6 mm |
Current design choices; parts may change before production. NXP, i.MX, EdgeLock, STMicroelectronics, STM32, Morse Micro, Texas Instruments, Rogers, PORON, Arm, Cortex, TrustZone, Wi-Fi HaLow and Bluetooth are trademarks of their respective owners.
Stronger than the phone
iPhone 18 Pro is an aluminium unibody with a Ceramic Shield back. The shell is Grade 5 titanium, which is stronger and harder than any aluminium alloy used in phones, so on the back it is a shield, not just a cover.
| Material | Yield strength | Note |
|---|---|---|
| Grade 5 titanium, Ti-6Al-4V (the shell) | at least 828 MPa (ASTM B348) | About 1.6× high-strength aluminium |
| 7075-T6 aluminium | about 500 MPa | The strongest common 7000-series alloy. Apple doesn’t publish the iPhone 18 Pro alloy. |
| C26000 brass, half hard (the brass shell) | about 360 MPa | Softer than titanium; chosen for its antimicrobial surface |
Drops: the physics
A phone dropped from 1.5 m hits the ground at √(2gh) ≈ 5.4 m/s. What breaks glass is how fast that speed goes to zero: stopping over a distance d means an average deceleration of v²/2d. A hard metal shell pressed straight onto the phone would pass its own 93 g into the phone in a rigid contact that stops within about 0.1 mm, around 15,000 g.
The shell is held on by a 0.5 mm microcellular urethane layer instead. In a back or edge impact the shell stops first and the layer lets the phone decelerate over about 0.3 mm of usable stroke, around 5,000 g on average: about a third of the rigid case. The layer firms up at impact speeds and returns to shape after each hit.
| Input | Value |
|---|---|
| Drop height | 1.5 m, the usual test height |
| Impact speed | 5.42 m/s |
| Phone mass | about 200 g |
| Energy at impact | 2.9 J for the phone alone, 4.3 J with the shell |
| Rigid stop | about 0.1 mm: 15,000 g average |
| Through the shock layer | about 0.3 mm of 0.5 mm: 5,000 g average |
The shell covers the back and frames the camera. It doesn’t cover the screen, so a drop flat onto the glass is still the iPhone’s Ceramic Shield 2 against the ground. These are first-order estimates; production shells are tested to MIL-STD-810H Method 516.8 drops at 1.2 m and 1.5 m onto steel-backed plywood, with the results published here.
Paired to your iPhone’s Secure Enclave
At setup, the khensu app creates a post-quantum ML-DSA-87 key inside your iPhone’s Secure Enclave (CryptoKit, iOS 26), usable only with Face ID, and signs the shell’s own identity key with it. The shell keeps its keys sealed in the i.MX 93’s EdgeLock Secure Enclave and takes instructions only from the paired key. It carries only sealed, fixed-size packets on a constant schedule, so it never holds a readable message or learns who is talking to whom. If you lose it, revoke it from your iPhone; there’s nothing on it for the finder to read.
No device can honestly be called unhackable. The design goal is narrower and testable: no single compromised part, whether the radio, the node computer or the network, can reveal content, metadata or your identity. The guard chip owns every radio, so even a compromised node computer can’t break the cover pattern. Firmware is open and reproducibly built.
Design documents and patents
The full design document, CAD and drawings are published here once the patent filings are complete.
See it on khensu.nu.