Bitcoin Seed Generator Entropy32 Plus Uses Radioactive Decay for True Randomness - Blockonomi
by Brenda Mary · BlockonomiTLDR:
Table of Contents
- Entropy32 Plus generates Bitcoin seed phrases using radioactive decay as its physical entropy source.
- A Geiger counter paired with an LM393 comparator captures decay timing for seed generation.
- SHA-256 conditioning whitens the raw radioactive entropy before mapping it to the BIP39 wordlist.
- The developer says entropy quality remains unvalidated under the NIST SP 800-90B methodology so far.
A Bitcoin seed generator that relies on radioactive decay for randomness has surfaced as a new open-source hardware project.
The device, called Entropy32 Plus, uses a Geiger counter to capture decay events. Their timing is then processed through SHA-256 conditioning before mapping to the BIP39 wordlist.
The build runs fully offline, with no wireless connectivity or stored seed data. Its developer notes the entropy has not yet been validated under NIST SP 800-90B.
How the Bitcoin Seed Generator Works
The core idea behind this Bitcoin seed generator is physical unpredictability. Standard software-based random number generators are deterministic, producing identical output from identical inputs every time.
Radioactive decay avoids that pattern entirely. Individual decay events occur at quantum-mechanically random intervals that cannot be predicted in advance, according to the project documentation.
A Geiger counter connected through a 3.5mm audio jack detects each decay pulse from a radioactive or background source.
An LM393 comparator then converts the raw voltage signal into a clean high or low reading. This conversion uses a fixed bias point set near 0.5V for consistency.
The timing gaps between successive pulses are captured by the onboard firmware. That data is passed through a SHA-256 conditioning stage to whiten it and remove statistical bias. The processed entropy is then mapped onto words from the standard 2048-word BIP39 English list.
The entire process runs on a custom PCB built around an ATmega328P microcontroller. It pairs with a small OLED display and a button-driven interface for on-device operation.
The project’s documentation describes the device as “simple, auditable, and buildable by anyone with readily available components.” No software beyond the onboard firmware is required to generate or view a completed seed phrase.
Hardware and Design Constraints
Fitting this Bitcoin seed generator onto a low-memory microcontroller required careful engineering decisions. The compiled firmware uses 30,006 bytes of the chip’s 30,720-byte flash limit. That leaves under 1,000 bytes of headroom for any future changes to the code.
The BIP39 wordlist alone accounts for 13,117 bytes, or roughly 43 percent of total program storage. The SHA-256 compression routine adds another 2,278 bytes to the total. Meanwhile, the state machine and onboard menu logic take up just over 3,000 bytes combined.
Because the wordlist consumes so much space, common display libraries could not fit alongside it. The project could not accommodate the widely used Adafruit_GFX and Adafruit_SSD1306 libraries as a result. The firmware instead communicates with the OLED screen through U8x8’s text-only mode to save memory.
The repository includes the full Arduino sketch, the SHA-256 implementation, and KiCad schematics. It also contains fabrication files and 3D-printable enclosure designs for anyone building the device.
The developer has described the build as experimental rather than independently audited. The documentation adds that users should verify the entropy source or proceed “at your own risk.”