One-Time Write RW2000 Ibutton Key Card — Hardware-Locked, Physically Anti-Tamper
For security integrators, government facility managers, and critical infrastructure operators who need on-site UID assignment with a non-negotiable guarantee: no one — not a tenant, not a locksmith, not an attacker with a programmer — can change the credential after it is deployed.
Every RW2000 Ibutton Key Card ships blank. The integrator writes the UID once, on site, using a TM Pro high-voltage programmer. After that single write cycle, the silicon die physically seals — not through a software flag, not through a lock bit that a skilled technician could reset, but through a one-time programmable fuse inside the chip that blows during the write pulse. The credential is now immutable at the hardware level. A tenant cannot clone it to a higher-privilege UID. A fired employee cannot re-assign it. A builder with access to the electrical room cannot swap a door key for a server-room key. The same 16 mm steel iButton in the same 15 mm wide ABS handle (55 mm total) as every other keyfob in the range — but with a silicon die that refuses a second write under any voltage, any protocol, any tool.
This is the chip you order when the access panel audit trail must be legally defensible. When a security clearance depends on the credential being provably single-assignment. When a national railway tracks 4,800 maintenance workers across signal posts and a mismatched UID could derail a maintenance audit. For every other deployment — rotating tenants, locksmith stock, quarterly re-issue — the RW1990 multi-write keyfob is the correct product. The RW2000 Ibutton Key Card does exactly one thing, and it does it with hardware certainty: write once, lock forever.
Three Products, Three Security Models — Where the RW2000 Ibutton Key Card Sits
| TM1990A-F5 (Read-Only) | RW1990 (Multi-Write) | RW2000 (One-Time Write) | |
|---|---|---|---|
| Initial state | UID factory-burned | Blank | Blank |
| Programmer | None — UID is permanent from fab | Standard TM handheld (5V) | TM Pro (high voltage) |
| Write cycles | 0 | > 100,000 | 1 — fuse blows, physically permanent |
| After deployment | Cannot change. De-authorise in panel. | Re-write, re-assign, recycle hardware. | Cannot change. No software or hardware path to overwrite. |
| Anti-tamper | Factory-level (fab-burned) | Software-level (write-lock flag) | Hardware-level (fuse — physically blown) |
| Best for | Fixed assignment: one person, one fob, lifetime | Rotating assignment: tenants, students, locksmiths | On-site setup with zero re-assignment risk: government, defence, critical infra |
If you already use TM1990A-F5 read-only keyfobs but want to assign UIDs on site rather than relying on factory-burned serials — the RW2000 Ibutton Key Card gives you that control without introducing the re-write risk of RW1990. The integrator writes a UID at installation. The chip refuses any subsequent write forever. The audit trail is clean because the credential is physically incapable of holding more than one identity.
Three Deployments That Depend on One-Time Write
Government facility — audit-trail integrity at the hardware level
A federal agency manages twelve office buildings with tiered access: general, restricted, and classified. Every employee and contractor receives an RW2000 Ibutton Key Card encoded on site by the agency’s own security team using a TM Pro programmer — no UIDs leave the building, no factory knows which serial maps to which clearance. The programmer writes the UID once. The on-chip fuse blows. The credential is now physically single-assignment.
When a contractor’s engagement ends, the security team de-authorises the UID in the Bolid S2000-Proxy panel — ten seconds of software work. The contractor still holds a physical token, but it opens nothing. And unlike an RW1990, the contractor cannot re-program it in the parking lot with a handheld tool to match a valid UID — because the chip’s write fuse is already destroyed. The credential is a dead piece of metal. The audit log shows a clean de-authorisation with no path to credential tampering. This is the distinction that passes a security audit without a footnote about “trusting the software lock.”
Railway signal-post access — 4,800 critical points, zero re-key risk
A national rail operator deploys 4,800 RW2000 Ibutton Key Cards to track maintenance workers across signal posts, relay rooms, and switching stations. Each signal post has a 1-Wire probe reader wired to a central logging system. Each worker’s keyfob is encoded once with a unique UID at the depot before the worker’s first shift. The logging system timestamps every touch event to the millisecond and maps it to the worker’s personnel file.
The security requirement is unambiguous: a worker who touched signal post A-47 at 03:14 must be the same individual for the entire employment record, and no field supervisor can re-assign that keyfob to a different worker to cover a missed inspection. With an RW2000, the credential identity is fused at the hardware level — the logging system knows that UID 0x1A3F… belongs to worker ID 2841, and it will belong to worker ID 2841 until the keyfob is physically destroyed. There is no re-write path. There is no “the supervisor used the TM programmer to swap assignments” scenario. The one-time write model is not a feature — it is a compliance requirement.
Cyfral intercom ecosystem — Eastern Europe standard
Across apartment blocks in Poland, Czech Republic, Slovakia, and the Baltic states, Cyfral and Metakom intercom panels are the dominant access control standard. These panels use the 1-Wire protocol with a specific UID format, and the RW2000 Ibutton Key Card is the standard blank credential in this ecosystem — often referred to as a “disposable marker” or “one-write key.” A building superintendent encodes a new tenant’s keyfob once with the Cyfral panel in programming mode, and that fob stays with the apartment until the tenant moves out. The credential is replaced, not re-encoded — a deliberate security choice that prevents a departing tenant from keeping a working key.
For a distributor serving the Eastern European access control market, the RW2000 Ibutton Key Card is not a niche product — it is the standard consumable. A property management company with 800 apartments orders 1,000 RW2000 keyfobs per year as part of routine tenant turnover logistics. The Cyfral ecosystem alone drives a predictable, recurring demand cycle that a distributor can forecast twelve months forward.
Custom Manufacturing — Five Lines, One Factory, Same Form Factor
The RW2000 Ibutton Key Card shares every external component with the TM1990A-F5 and RW1990: the same 16 mm SUS304 stainless steel housing, cold-formed through an eight-station progressive die; the same 15 mm wide virgin ABS handle, injection-moulded on 120-ton Haitian machines at a single Shenzhen campus; the same crimping station that seals the die against the F5 can rim. The difference is entirely in the silicon die — an OTP (one-time programmable) fuse architecture that physically breaks the write path after the first programming pulse — and the QC protocol that verifies it.
Customisation is identical across the range: seven stock colours (black, blue, red, yellow, green, white, grey) with custom Pantone matching above 5,000 units; silk-print logo with ±0.3 mm registration; laser-etched serial numbers with CSV UID mapping. Handle colours, logo placement, and serial formatting are consistent regardless of which chip is inside — a property manager can order TM1990A-F5 for permanent residents, RW1990 for guest suites, and RW2000 for high-security areas, all with the same brand print and colour-coding scheme.
RW2000 Ibutton Key Card Technical Specifications
| Parameter | Value |
|---|---|
| Puce | RW2000 — one-time programmable (OTP) 1-Wire ROM, high-voltage write, hardware fuse lock |
| UID | 64-bit ROM, single write cycle only — fuse blows after first programming pulse |
| iButton housing | F5 SUS304 stainless steel, Ø 16.0 mm, thickness 5.5 mm |
| Handle | Virgin ABS, injection-moulded, 15 mm wide, 55 mm total length (key-ring hole to steel face) |
| Poids | ~8 g per unit |
| Protocole | Dallas/Maxim 1-Wire, 15 kbps standard / 142 kbps overdrive, Manchester encoding |
| Read method | Touch-contact, parasitic-powered — no battery, no RF field |
| Read speed | < 5 ms at 142 kbps overdrive |
| Write method | High-voltage pulse via TM Pro programmer only — Flipper Zero, Arduino, and standard TM handheld tools cannot write |
| Write cycles | 1 — hardware fuse physically prevents any subsequent write |
| Operating temp | −40°C to +75°C |
| Ingress protection | IP64 (splash-proof); overmoulded IP67 version on request |
| Durée de vie | > 10 years |
| Handle colours | Black, blue, red, yellow, green, white, grey; custom Pantone (MOQ 5,000) |
| Custom marking | Silk-print logo (±0.3 mm registration) + laser-etched serial number with CSV mapping |
| Emballage | 100 pcs / inner box; 5,000 pcs / carton (73 × 24 × 33 cm, 25 kg) |
| Monthly capacity | > 2,000,000 pcs across five in-house production lines |
| Certifications | ISO 9001:2015, CE |
| Ecosystem | Cyfral, Metakom, Bolid, Iron Logic, Rubezh, ZKTeco, Anviz, railway access systems, government facility panels |
Quality Control — Verifying the One-Time Write
OTP QC is fundamentally different from multi-write QC. On the RW2000 Ibutton Key Card line, a random 200-unit sample from every batch undergoes a destructive verification protocol. Stage one: all 200 units are written with a test UID via TM Pro — a single write-read failure triggers a full batch investigation. Stage two: all 200 units are then subjected to a second high-voltage write pulse with a different UID, followed by a read-back at both 15 kbps and 142 kbps overdrive. The read-back must return the FIRST UID, not the second — confirming that the fuse blew correctly and the chip ignored the second write attempt. A single unit returning the second UID triggers a batch-wide rejection. Stage three: twenty units are cross-sectioned and inspected under an electron microscope for fuse-gap verification. Stage four: the standard mechanical QC — caliper, drop test, visual inspection, colour drift — identical to the TM1990A and RW1990 lines. The full QC dossier ships with every pallet.
Frequently Asked Questions
What happens if I try to re-write an RW2000 Ibutton Key Card?
Nothing. The chip physically ignores the write command. After the first successful programming pulse, the on-chip fuse is destroyed — the electrical path that carries the write voltage to the memory cell no longer exists. Any subsequent write attempt, whether from a TM Pro programmer, a Flipper Zero, or a custom microcontroller, will fail silently. The UID read-back will always return the original value. This is not a software behaviour — it is a hardware property of the silicon die.
Can I use a standard TM handheld programmer to write the RW2000?
No. The RW2000 Ibutton Key Card requires a high-voltage write pulse that is only generated by the TM Pro programmer. Standard TM handheld tools, Arduino-based programmers, Flipper Zero, and Proxmark3 operate at standard 5V or 12V logic levels and cannot trigger the OTP write cycle. We supply the TM Pro programmer bundled with your first RW2000 order or as a standalone tool.
How do I know the fuse actually blew after writing?
Attempt a second write with a different UID, then read back. If the read-back returns the first UID — the fuse blew correctly. If it returns the second UID — the chip is defective and should not have passed QC. Our destructive batch sampling verifies this on 200 units per production lot, and the QC dossier includes the pass/fail count. In the field, every integrator should perform this two-write verification as part of their commissioning procedure.
Is the form factor different from the RW1990?
Identical externally. Same 16 mm SUS304 steel housing, same 15 mm wide ABS handle, same 55 mm total length, same ~8 g weight, same seven stock colours, same silk-print and laser-etch options. A site can use TM1990A-F5 for permanent staff, RW1990 for rotating contractors, and RW2000 for high-security zones — all with indistinguishable physical appearance. The only way to tell which chip is inside is the QC label on the inner box and the UID behaviour after a write attempt.
What is the minimum order and lead time?
Free evaluation kit — ten RW2000 Ibutton Key Cards plus one TM Pro high-voltage programmer — ships within three business days to any verified company address. Pilot order: 500 units at standard tier pricing. Production orders start at 1,000 units with a fourteen to twenty-one working day lead time for stocked colours. Custom Pantone and laser-etched serials add seven to ten working days. TM Pro programmers are sold separately or bundled at a discount with first orders above 2,000 units.
Request a Free Evaluation Kit
Tell us your deployment scenario — government facility, railway infrastructure, Cyfral intercom network, or custom high-security integration. We ship ten RW2000 Ibutton Key Cards in mixed handle colours, plus one TM Pro high-voltage programmer, within three business days. Test the one-time write cycle, verify the fuse behaviour, and confirm compatibility with your reader fleet before committing to a production order.
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