# Enigma Witness Vault Buying Guide This guide is for buying commodity parts for the Raspberry Pi Zero 2 W Enigma Witness Vault hardware package. It targets a practical $50-$100 build before shipping/tax, depending on reseller, regional availability, optional NFC, and how many fasteners/cables you already have. Claim boundary for buyers: > Buying this hardware gives you a buildable local custody/witness appliance for Enigma demos and deployments. It does not buy provider deletion, model forgetting, tamper-proof storage, guaranteed compliance, token upside, or complete side-channel absence. ## Reference bill of materials | Part | Required | Target spec | Typical notes | | --- | --- | --- | --- | | Raspberry Pi Zero 2 W | Yes | 65 x 30 mm board, quad-core A53, 512 MB RAM, Wi-Fi/BLE, microSD, USB OTG | Buy with soldered 40-pin header if you want fastest assembly. | | microSD card | Yes | 16 GB or larger, high-endurance preferred | Buy reputable brand; keep one spare imaged card. | | ATECC608A breakout | Yes for hardware-backed witness demo | I2C, fixed address `0x60`, about 25.5 x 17.7 x 4.7 mm | Adafruit breakout is a known target; avoid unknown clones for public demos. | | SSD1306 OLED | Yes | 0.96 in, 128 x 64, I2C, common address `0x3C` or `0x3D` | Match PCB dimensions and pin order, not just screen size. | | PN532 NFC module | Optional | Compact module envelope about 43.6 x 41 x 3.9 mm | Requires the longer NFC enclosure variant. | | Enclosure filament | Yes | PETG or ASA | Avoid conductive/carbon-filled filament near Wi-Fi/BLE/NFC antennas. | | Fasteners/inserts | Yes | M2/M2.5 screws and matching heat-set inserts | Buy extras; small screws disappear during conference setup. | | Wiring/connectors | Yes | Short jumpers or JST-SH/JST-PH harnesses | Use flexible wire and strain relief. | | USB power/data cable | Yes | Known-good cable for Pi power/service | Many cheap cables are charge-only; test before demo day. | | Power supply | Yes | Stable USB supply suitable for Pi Zero 2 W and sidecars | Avoid marginal laptop hubs during public demos. | | NFC tags/cards | Optional | Compatible with PN532 demo flow | Use tags containing only capsule identifiers or demo pointers. | Reference design constants to preserve when comparing listings: - Pi Zero 2 W board envelope: 65 x 30 mm. - NFC-capable enclosure: 86 W x 102 L x 28 H mm. - No-NFC enclosure: 86 W x 78 L x 28 H mm. - NFC variant Pi mount reference origin: `[10.5, 64]`. - Pi mounting-hole offsets from the Pi board origin: `[3.5, 3.5]`, `[61.5, 3.5]`, `[3.5, 26.5]`, `[61.5, 26.5]`. - ATECC608A target breakout: about 25.5 x 17.7 x 4.7 mm, fixed I2C address `0x60`; advisor target price was $4.95 from Adafruit, but buyers must confirm current price and stock. - OLED target: 0.96 in 128 x 64 SSD1306 I2C, usually `0x3C` or `0x3D`. - Optional compact PN532 target envelope: about 43.6 x 41 x 3.9 mm. - Printer/material target: Bambu X1 Carbon-class 256 x 256 x 256 mm build volume, 0.4 mm hardened nozzle, PETG or ASA. Budget planning bands, before tax/shipping: | Build | Expected parts range | What changes the price | | --- | ---: | --- | | No-NFC reference unit | $50-$75 | Pi stock, whether the header is pre-soldered, and whether you already own screws/filament. | | NFC-capable unit | $65-$100 | Adds PN532, NFC tags, lid harness/connectors, and the longer printed enclosure. | | Conference-ready unit with small spares | $80-$100 | Stays in target by adding spare cable, microSD, fasteners, and printed lid; buy duplicate electronics as event inventory, not per-unit BOM. | Treat these as procurement targets, not promises. If a cart is far below the low end, check for counterfeit, wrong, or missing parts. If it is far above the high end, remove decorative accessories before changing the reference design. ## Where to buy Prefer reputable sources over the absolute cheapest marketplace listing. For public demos, predictable parts are worth more than saving a few dollars. ### Raspberry Pi reseller search terms Use official or established Pi resellers first. Good starting places are official Raspberry Pi Approved Resellers and established electronics suppliers. Search the reseller catalog first, then marketplace listings only for commodity accessories. Reseller lookup terms: - `Raspberry Pi Approved Reseller Zero 2 W` - `Raspberry Pi Zero 2 W official reseller` - `Raspberry Pi Zero 2 W WH header official` - `PiShop Zero 2 W header` - `The Pi Hut Zero 2 W header` - `CanaKit Raspberry Pi Zero 2 W` - `Vilros Raspberry Pi Zero 2 W` Search terms: - `Raspberry Pi Zero 2 W with header` - `Raspberry Pi Zero 2 WH` - `Raspberry Pi Zero 2 W GPIO header kit` - `Raspberry Pi Zero 2 W microSD power supply kit` Quality checks: - Confirm it is `Zero 2 W`, not original `Zero W`. - Confirm whether the 40-pin header is soldered. - Confirm board is new, not a salvage pull. - Confirm reseller is not bundling a weak power supply or charge-only cable as the only USB cable. - Confirm shipping date; Pi stock can vary quickly. Acceptable substitutes: - Raspberry Pi Zero 2 W without header, if you can solder a 40-pin header cleanly. - A small Linux board only for internal experiments, not for the reference enclosure/demo, unless you update CAD, pinout, power, and software notes. Avoid: - Original Raspberry Pi Zero W sold as `Zero 2`. - Boards with damaged microSD slots or missing antenna components. - Mystery `Pi-compatible` boards for the launch reference build. - Kits that hide the exact board revision or include no data-capable USB path. ### Adafruit search terms Adafruit is the cleanest source for the ATECC target module and often stocks reliable OLED/NFC options. Search terms: - `Adafruit ATECC608A breakout I2C 0x60` - `Adafruit ATECC608A STEMMA QT` - `Adafruit SSD1306 0.96 128x64 I2C OLED` - `Adafruit PN532 NFC RFID breakout` - `STEMMA QT cable 4-pin JST SH` Quality checks: - ATECC module should clearly say ATECC608A, I2C, and fixed address `0x60`. - Confirm connector type if using STEMMA QT/Qwiic cables. - Confirm OLED voltage and pin order. - Confirm PN532 module dimensions fit the selected enclosure variant. - Buy cables from the same ecosystem when possible to avoid connector mismatch. Acceptable substitutes: - SparkFun/Qwiic-compatible ATECC608A breakout only if it exposes I2C cleanly and fits the mount. - Any reliable SSD1306 0.96 in 128 x 64 I2C OLED if its PCB fits the window/retainer and address is `0x3C` or `0x3D`. - PN532 breakout from a reputable electronics supplier if it fits the 43.6 x 41 x 3.9 mm envelope or you are willing to adjust the enclosure. Avoid: - ATECC modules that do not identify the chip revision. - SPI-only OLEDs for this reference build unless you intentionally rewire and update software. - OLEDs advertised only as `0.96 I2C` with no controller name, no voltage information, and no dimensions. - PN532 boards with large antenna plates that will not fit the enclosure. ### Amazon search terms Use Amazon for commodity pieces, not the parts where authenticity matters most. Search terms: - `Raspberry Pi Zero 2 W header` only if official reseller stock is unavailable - `0.96 inch OLED I2C SSD1306 128x64 4 pin` - `PN532 NFC RFID module I2C compact` - `M2.5 heat set inserts assorted kit` - `M2 M2.5 nylon washers screws kit` - `JST PH 2.0 4 pin cable` or `JST SH 1.0 4 pin cable` - `PETG filament 1.75mm black` - `ASA filament 1.75mm natural black` - `USB data cable micro USB short` Quality checks: - Read the pin labels in product photos. OLED boards often use different orders: `GND VCC SCL SDA` vs `VCC GND SCL SDA`. - Prefer listings with actual board dimensions in millimeters. - Prefer items with clear controller names: `SSD1306`, `PN532`, `ATECC608A`. - For filament, confirm it is normal PETG/ASA, not carbon-fiber, metal-filled, glitter-filled, or conductive. - For screws/inserts, confirm thread size and length. M2.5 screws are common for Pi mounting. - For USB cables, look for explicit `data` or `sync`, not charge-only language. Acceptable substitutes: - Generic SSD1306 I2C OLED for internal builds after you verify address, voltage, and pinout. - Generic fastener kits if screws are straight, threads are clean, and lengths match the enclosure. - Generic NFC tags for demos if they are compatible with the PN532 and contain no secrets. Avoid: - Carbon-fiber PETG/ASA or conductive filament for the enclosure. - Random `secure element` modules that are not ATECC608A. - OLEDs with SH1106 controller unless the software/display driver is adjusted. - PN532 modules that require 5 V signaling when your wiring plan is 3.3 V. - `micro USB charging cable` listings that do not mention data. - Large metal NFC stickers mounted near the antenna or Pi radio. ## Buying plan by build type ### Minimum no-NFC demo build Use the shorter 86 W x 78 L x 28 H enclosure. Buy: - Raspberry Pi Zero 2 W with header. - microSD card. - ATECC608A I2C breakout. - 0.96 in SSD1306 I2C OLED. - PETG or ASA filament. - M2/M2.5 screws, heat-set inserts, nylon washers. - Short wiring/connectors. - Known-good USB power/data cable and power supply. Best for: - 5-minute conference demos. - Local custody/witness proof loop. - Lower BOM cost and simpler assembly. Do not claim: - NFC capsule tap. - Physical air gap. - Tamper-proof storage. ### NFC-capable demo build Use the longer 86 W x 102 L x 28 H enclosure. Buy everything in the minimum build plus: - Compact PN532 NFC module near the 43.6 x 41 x 3.9 mm envelope. - NFC tags/cards for capsule identifiers. - A removable lid harness if PN532 mounts to the lid. Best for: - Stage demos where a physical tap makes the capsule concept memorable. - Booth demos where attendees can see an object-to-capsule handoff. Do not claim: - NFC proves identity by itself. - NFC tags securely store private memories by default. - NFC implies token ownership, rewards, or investment value. ### Spare/demo fleet build For every 3 public demo units, buy extras: - 2 extra microSD cards. - 2 extra USB data cables. - 1 extra OLED. - 1 extra ATECC608A breakout. - 1 extra PN532 if using NFC. - 1 full spare screw/insert/washer set. - 1 extra printed lid and 1 extra printed base if travel risk is high. Best for: - Conferences. - Press days. - Partner workshops. - Hardware hand-carry travel. ## Parts to buy extras of Buy extras because these fail, get lost, or vary between listings: - microSD cards: imaging mistakes and corrupt cards are common demo killers. - USB data cables: charge-only cables look identical under pressure. - M2/M2.5 screws: lengths get mixed during assembly. - Heat-set inserts: overheated or crooked installs happen. - Nylon washers: useful for isolating boards from screw heads. - OLED modules: glass and ribbon assemblies are fragile. - STEMMA QT/Qwiic/JST cables: connector ecosystems are easy to mismatch. - NFC tags: public demos need clean, replaceable tags with safe payloads. - Printed lids: display windows and NFC surfaces take abuse in travel. ## Substitute parts Substitutions are fine for internal builds; public launch units should stay close to the reference BOM. ### Pi board substitutes Allowed for internal experiments: - Pi Zero 2 W without soldered header. - Other small Linux SBCs if the software path works and the enclosure is redesigned. Not recommended for launch reference: - Original Pi Zero W: lower performance and easy to confuse with Zero 2 W in public materials. - Full-size Raspberry Pi boards: different footprint, ports, thermals, and enclosure. - Microcontroller-only boards: not the same local Linux vault appliance story. ### Secure element substitutes Allowed with engineering approval: - Another ATECC608A breakout with reliable I2C, documented pinout, and physical fit. Not equivalent without engineering work: - TPM modules. - Smart cards. - Hardware wallets. - Random `crypto authentication` boards without ATECC608A documentation. Claim rule: - If the substitute is not ATECC608A and not integrated into the software flow, do not use ATECC-specific claims. ### OLED substitutes Allowed: - SSD1306 0.96 in 128 x 64 I2C display at `0x3C` or `0x3D`, if the PCB fits. Requires changes: - SH1106 displays. - SPI displays. - Larger OLEDs. - Displays with different mounting hole positions. Claim rule: - If the display does not show live device status, call it a decorative display, not operator status. ### NFC substitutes Allowed: - Compact PN532 module that fits the NFC enclosure and voltage/pinout plan. Requires changes: - Larger PN532 antenna boards. - USB NFC readers. - Phone-only QR/NFC flows. Claim rule: - If PN532 is absent, do not mention NFC capsule tap in the live demo. ### Filament substitutes Recommended: - PETG: easiest durable default. - ASA: higher heat tolerance, needs ventilation and better print setup. Avoid for radio/NFC builds: - Carbon-fiber-filled filament. - Conductive filament. - Metal-filled filament. - Magnetic or abrasive specialty filament near antennas. Allowed for prototypes: - PLA for fit-check prototypes only, not preferred for durable travel demos. ## Bad purchases to avoid Avoid these even if cheap: - Original Pi Zero W mislabeled as Pi Zero 2 W. - Pi boards with no clear seller, no return path, or suspiciously low prices. - ATECC modules that do not say ATECC608A. - OLEDs that do not identify SSD1306 or list dimensions/pinout. - SH1106 OLEDs sold as SSD1306-compatible without driver confirmation. - SPI OLEDs when the wiring/software plan expects I2C. - PN532 boards too large for the enclosure. - NFC modules that require voltage shifting you are not adding. - Charge-only USB cables. - Weak or noisy USB power supplies. - Brittle low-quality filament for travel units. - Carbon-filled, conductive, metal-filled, or glitter filament near antennas. - Loose metal standoffs that can contact PCB pads. - Adhesive-only board mounting for public demo units. - Mystery `AI crypto vault` gadgets that do not match the reference BOM. - Tags/cards preloaded with unknown URLs, credentials, or vendor apps. ## Incoming inspection checklist Check each part before assembly day. ### Pi Zero 2 W - Board marking confirms Raspberry Pi Zero 2 W. - microSD slot is intact. - USB/power connectors are firm. - Header is straight and solder joints look clean, or header kit is present. - No visible antenna damage. ### ATECC608A breakout - Chip/module is labeled ATECC608A in listing or board documentation. - I2C pins are labeled. - Address expectation is `0x60`. - Connector/cable ecosystem matches your harness plan. - Mounting holes or adhesive area fit the enclosure mount. ### OLED - Controller is SSD1306. - Resolution is 128 x 64. - Interface is I2C, 4-pin. - Address is expected to be `0x3C` or `0x3D`. - Pin order is documented. - PCB fits the window/retainer, not just the glass. ### PN532 - Module is PN532. - Board envelope fits the NFC enclosure. - Voltage mode matches wiring plan. - Antenna is not blocked by metal backing. - Connector route can survive lid opening. ### Filament and printed parts - Material is PETG or ASA for demo units. - No conductive/carbon/metal fill. - Base and lid match NFC or no-NFC variant. - Pi mount corresponds to the selected CAD variant. - OLED window and PN532 surface are clean. ## Conference procurement checklist For one public demo unit, pack: - Assembled Witness Vault. - Spare microSD card. - Spare USB power/data cable. - USB power adapter. - Small screwdriver. - Tweezers or spudger. - 2-4 spare screws for each size used. - Spare NFC tag if using NFC. - Printed proof-boundary placard. - Laptop fallback bundle and local CLI demo path. For three public demo units, add: - One spare OLED. - One spare ATECC608A breakout. - One spare PN532 module if NFC is part of the show. - Spare printed lid/base. - Spare jumper/JST cable set. - Extra microSD cards already imaged. ## Budget control To stay near the $50-$100 commodity target: - Use Pi official reseller pricing where possible. - Skip NFC on the first build if budget is tight. - Buy one good fastener kit rather than many tiny one-off packs. - Use PETG unless ASA is needed. - Do not buy decorative displays, batteries, touchscreens, cameras, or metal enclosures for the reference demo. - Do not buy premium `security appliance` parts that create claims the software/hardware package does not support. Do not reduce cost by buying: - unverified Pi clones, - unknown secure-element clones, - charge-only cables, - conductive filament, - no-name power supplies for public demos, - parts that force last-minute CAD or software changes. ## Seller questions to ask Ask these before buying for a public launch unit: - Is the board definitely Raspberry Pi Zero 2 W, not Zero W? - Is the GPIO header soldered? If not, is a compatible header included? - Does the ATECC breakout use I2C and address `0x60`? - Is the OLED SSD1306, 128 x 64, I2C, and what is the pin order? - What are the OLED PCB dimensions and mounting hole positions? - What are the PN532 board dimensions and voltage requirements? - Is the USB cable data-capable? - Is the filament plain PETG/ASA with no conductive, carbon, or metal fill? - Can the seller replace defective boards quickly before the event? ## Safe buying summary If you need the shortest safe purchase list, buy: 1. Raspberry Pi Zero 2 W with soldered header from an official Pi reseller. 2. Adafruit ATECC608A I2C breakout. 3. SSD1306 0.96 in 128 x 64 I2C OLED with known dimensions. 4. 16 GB or larger high-endurance microSD card. 5. Plain PETG filament. 6. M2/M2.5 screws, heat-set inserts, nylon washers. 7. Short data-capable USB cable and reliable USB power supply. 8. Optional compact PN532 and blank NFC tags only if building the NFC enclosure. That list builds the public story cleanly: commodity hardware, visible local state, ATECC-backed witness identity, scoped Enigma receipts, and honest boundaries.