Hi, this is apalok21, founder of cryobrick, and a Bitshala fellow. I wanted reliable cold storage for our Bitcoin. Like most people, I started shopping around for hardware wallets, but the market left me deeply frustrated.
The reputable devices were expensive. Many required a steep technical learning curve. But my biggest issue was physical security: almost every single device on the market screams “I hold Bitcoin” the moment you look at it. They look like high-tech crypto gadgets. They are easily spotted by border agents, airport security, or anyone looking through your belongings.
This security flaw is magnified in emerging economies and high-risk areas, the exact places where financial self-custody is a necessity, not a hobby. People in these regions often cannot afford a $150 customized wallet, and carrying a device that obviously holds digital wealth is a massive physical liability.
So, I did what any stubborn Bitcoiner does: I built my own solution.
My first iteration was a DIY air-gapped setup: an SD card running a heavily modified, completely locked-down version of Puppy Linux paired with Electrum. It worked beautifully.
A year or two later, Tails OS released a similar streamlined approach with far less friction. If you want a solid, zero-cost cold storage option using what you already own, there is a full walkthrough video on it here: youtu.be/XQ5EjApvlEQ
But even a bulletproof DIY Cold Storage solution has a psychological bottleneck. Most Bitcoiners are terrified to plug a seed phrase or a hardware wallet into any laptop or PC that isn't their own personal, trusted machine. Even if the system is mathematically secure and completely air-gapped, the lingering anxiety of compromise is real. People simply don't trust the glass and keyboard of a standard PC.
That’s when it hit me. We didn't need better software on a laptop. We needed a completely different physical form factor.
We needed something cheap, utterly inconspicuous, and universally understood. We needed a feature phone.
Building CryoBrick: Zero Funding, Pure Hacker Space Grit
The vision was simple: build an affordable, secure Bitcoin cold storage wallet disguised entirely as a legacy feature phone.
Me and @Anipy1 (Bitcoin Software Developer) pitched the concept in the Angor Pitch Contest at the Bitshala BOSS Summit in Goa back in October 2025. By then, my partner Anipy was already on board to handle the application development, and the concept resonated enough to take second place in the Contest. From that moment on, the clock started ticking.
There was just one catch: I am not a developer or a hardware engineer.
I had to learn the hardware side completely from scratch. I spent endless hours at Bitshala Bitspace Goa, the local grassroots Bitcoin hackerspace obsessing over jailbreaking, flashing custom bootloaders, sideloading, and obtaining root access on low-spec chipsets. It was an exhausting cycle of trial, error, and bricked devices. But through that intense grind inside Bitspace, surrounded by fellow builders, I eventually established a reliable hardware baseline.
While I fought the hardware aspects of the device at Bitspace, Anipy took over the app development. Anipy took the UX workflows and turned them into a functional application. Operating on low-spec legacy hardware meant battling constant memory constraints, optimization bugs, and hardware bottlenecks. But exactly two months after that pitch in Goa, we officially launched the first iteration of CryoBrick in January 2026, right out of Bitspace Goa.
First iteration of CryoBrick in January 2026
We did this with absolutely zero outside funding. Version 1 was bootstrapped entirely out of our own pockets from start to finish. We didn't wait for a grant, an investor, or permission to build. We just built it in the hackerspace and shipped it.
https://x.com/cryobrick/status/2007346189377904836?s=20
True to our open-source ethos, Version 1’s software application has been completely transparent from day one. You can inspect the codebase right now on our GitHub repository.
While the software for Version 1 is fully open-source and publicly auditable, open-sourcing the hardware side presented a severe practical bottleneck. The V1 legacy feature phones rely on obsolete, out-of-production chipsets whose manufacturing was halted around 2021, making reliable physical sourcing nearly impossible for the average user. Furthermore, low-level flashing and bootloader exploitation on these devices require navigating proprietary, closed-source KaiOS architectures, an intricate, low-level process where even a minor partition error risks permanently bricking the device. Because of these supply chain and tooling constraints, delivering pre-flashed hardware was the only viable path for V1.
Total Congruency: Security Beyond the Surface#
There is a major flaw with most "disguised" hardware wallets on the market: they look like an everyday object on the outside, but the millisecond someone powers them on, the interface immediately gives the secret away.
We designed CryoBrick with absolute visual and functional congruency. It doesn't just look like a feature phone; it actually functions like one.
When you turn on the device, the hardware body and the user interface match perfectly. By default, the wallet app masquerades as an ordinary utility, like a functional Compass app. For users seeking a different look, the interface can be customized to look entirely like dummy retro games, such as Snake or Tetris.
To break past this decoy layer and access the cold storage suite, the user must input a specific, hidden user generated 6-digit PIN. If anyone handles the device, forces you to turn it on, or browses the UI, they see nothing but a standard, low-cost burner phone. This provides true, unassailable plausible deniability.
Mitigating the Hardware Vulnerability: Cryptographic Level Protection#
Building a secure wallet on cheap, off-the-shelf feature phone hardware presents another massive engineering hurdle: the lack of a dedicated Secure Element (hardware chip). On standard hardware, this creates a major vulnerability, if an attacker extracts the device's flash memory, they could potentially steal a raw seed phrase.
We mitigated this entirely at the software and cryptographic layer, making CryoBrick mathematically just as secure as expensive, purpose-built hardware wallets.
CryoBrick is safe & unaffected by recent Seed Phrase entropy bugs! We use standard software CSPRNG via device-level system entropy to generate unique 128-bit keys.
"System noise" means your phone captures random, microscopic clock-cycle timing variations between background tasks.
CryoBrick matches titans like BlueWallet & Electrum, giving the same 128-bit entropy output as dedicated chips.
Want 100% trustless security? The Code is open! We are currently working on adding manual dice & coin flip inputs.
While the 6-digit PIN gets you past the superficial "dummy" user interface, the true security lies deeper:
No Raw Storage: The seed phrase is never saved in plain text anywhere on the device's storage memory.
The Encrypted Blob: The cryptographic data is stored strictly as a heavily encrypted blob.
Dynamic Decryption: To view the seed phrase or sign a transaction, the user must input a unique, user-generated password. This password dynamically decrypts the cryptographic blob directly in volatile temporary memory, which is immediately wiped after execution.
Without this master password, extracting the physical data from the phone's memory chips yields nothing but useless, scrambled code.
Real-World Friction Testing#
CryoBrick doesn't try to be an all-in-one financial dashboard. It handles the core essentials of sovereign custody: it generates/restores a single-signature wallet and signs transactions. That's it.
Because of the low-spec camera and strict hardware limitations of Version 1, we bypassed camera based QR code signing entirely, designing the system to sign PSBTs (Partially Signed Bitcoin Transactions) via SD card or secure USB tethering.
We didn’t just build a prototype; we shipped real hardware.
To date, we’ve sold dozens of units with dozens more in the pre-order pipeline. The ultimate validation hasn't been the sales numbers, though, it’s been the user feedback. We have customers who have already used CryoBrick as a secondary Bitcoin storage device and traveled across international borders with a CryoBrick in their pocket, completely unbothered, experiencing the psychological relief of carrying their savings in a device that looks like a $20 feature phone.
Moving Beyond the Wallet#
As we put these devices out into the wild, we realized this form factor solves a second critical problem: secure, off-grid communication in environments facing heavy censorship or internet blackouts.
We integrated a simple Nostr chat app and a BitChat mesh networking client directly into the OS. While Version 1’s legacy Bluetooth hardware makes maintaining constant, stable mesh connections a technical challenge, the proof of concept is there. It proved that CryoBrick has massive utility not just for Bitcoiners, but for journalists, activists, and privacy advocates who need an unassailable, off-grid communication tool that blends into the background.
The Roadmap to Version 2: Unstoppable Execution#
We are currently deep in R&D for Version 2.
Version 1 proved the market demand and validated our cryptographic approach; Version 2 will perfect the hardware execution. We are moving to a brand-new hardware architecture designed to overcome our initial bottlenecks. Version 2 will feature optimized camera hardware, shifting QR-based camera signing to our primary transaction method. We are also introducing robust Bluetooth Low Energy (BLE) capabilities to make the off-grid mesh communication incredibly stable.
Most importantly, Version 2 is designed to be entirely open-source at the hardware level too.
Version 2 entirely eliminates version 1’s hardware dependency. By migrating to widely available modern feature phone chipset architectures running an open AOSP base, we are liberating the hardware layer alongside the software. Along with our firmware releases, we will publish complete, step-by-step DIY flashing blueprints and partition files to our GitHub. Users will no longer have to rely on us to procure or flash the device, anyone, anywhere in the world will be able to source an off-the-shelf feature phone and independently build their own sovereign stealth wallet from scratch.
The landscape has changed a bit since V1. My partner Anipy had to step back due to personal reasons and commitments. At the same time, while we have cleared initial screenings for open-source grants from prominent organizations like the Human Rights Foundation (HRF), nothing is set in stone.
But let me be absolutely clear: the development of Version 2 does not depend on funding or external help.
With Anipy out of the picture, I am prepared to take the reins completely. With or without outside funding, I will bootstrap Version 2 entirely by myself using my personal funds. The research is locked in, the hardware specifications are set, and this device will see the light of day.
Sovereign tools don't wait for permission. And they don't stop for budgets.
Support the Vision#
If you believe that self-custody should be affordable, invisible, and accessible to anyone regardless of geography or economic status, you can support our development by donation or contribute to our codebase:
Source Code: Explore and audit our software on https://github.com/cryobrick
Lightning Address: cryobrick@blink.sv Main Chain Address: bc1qlcz4yalqkqtdmtrh5ypp274ql6cqsrazzkm9j8 Geyser Fund: https://geyser.fund/project/cryobrick?hero=geyserpromotion
We would really appreciate it if you also showed your support by following our social media handles on various platforms.
https://x.com/cryobrick
https://youtube.com/@cryobrick?si=uXsw_ixy8bCuYbsw
Nostr: 
Cryobrick
Let’s make financial privacy completely accessible and affordable.
- Apalok @apalok21 Founder, CryoBrick
*This article is written by @apalok21 and published by @bitshala_org.
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