This Bitcoin Seed Generator Uses Radioactive Decay for Entropy — Inside the Open-Source Entropy32 Plus

An open-source hardware project dubbed “The Universe Bifurcator” turns Geiger-counter pulses into 12- and 24-word recovery phrases — entirely offline

A new open-source Bitcoin seed generator has taken an unusual route to randomness: radioactive decay. Published on GitHub in September 2026 by developer Alexander Higgins, the Entropy32 Plus project converts the unpredictable timing of atomic decay events into standard BIP39 recovery phrases — the 12- or 24-word sequences that control access to a Bitcoin wallet — using a fully offline hardware device with no wireless connectivity of any kind.

The project, which its creator nicknamed “The Universe Bifurcator,” is explicitly experimental. Higgins describes it as an educational undertaking and warns users not to trust it with substantial funds before it has undergone independent review. For Bitcoin holders who treat seed generation as the single most security-critical step in self-custody, the project is a fascinating case study in physical entropy — and in how much verification still remains undone.

How decay timing becomes wallet entropy

Radioactive decay is unpredictable at the level of individual atoms, which makes the arrival time of each decay event a candidate source of true randomness. Entropy32 Plus accepts pulses through a 3.5-millimeter connector from a GQ Electronics GMC-320S Geiger counter, which can detect emissions from either a radioactive source or plain background radiation. An LM393 comparator converts the counter’s analog signal into a digital pulse, which is passed to an ATmega328P microcontroller — the same chip family that powers classic Arduino boards.

The firmware records each accepted event with a microsecond timer and compares consecutive intervals. When the latest interval is longer than the one before it, the device records a one; when it is shorter, a zero. Equal intervals are discarded, and measurements below 200 microseconds are rejected as possible glitches. Collection continues until the device has assembled a 512-bit pool — exactly twice the 256 bits needed for a 24-word phrase.

SHA-256 conditioning, then BIP39 mapping

Once the pool is complete, the firmware processes all 64 bytes through a bundled SHA-256 implementation. Hashing does not create randomness; it spreads whatever entropy exists across the output and masks visible patterns linked to detector dead time, count-rate drift or correlations between measurements. The device uses the first 16 bytes of the hash for a 12-word phrase or all 32 bytes for a 24-word phrase, then follows the standard BIP39 specification: 128 bits plus a four-bit checksum for twelve words, or 256 bits plus an eight-bit checksum for twenty-four, divided into 11-bit indexes that each select one word from the standardized 2,048-word list.

The engineering is tight enough that the complete BIP39 English wordlist — 13,117 bytes — occupies roughly 43 percent of the microcontroller’s flash capacity. With the OLED interface, SHA-256 code and collection logic included, the compiled firmware fills 30,006 of the chip’s 30,720 available bytes, leaving just 714 bytes to spare.

Designed for offline seed generation

The published hardware files list no Wi-Fi, Bluetooth or other wireless components. Users operate the generator with two buttons and read the phrase from a 0.91-inch OLED screen. Generated word indexes live temporarily in RAM only; after the user transcribes the phrase, pressing both buttons triggers a confirmation process that overwrites the word array, clears the entropy pool and restarts collection. Hash, checksum and entropy buffers are wiped after the BIP39 indexes are calculated, and the design includes no persistent seed storage.

The firmware also runs a startup self-test, hashing the string “abc” and comparing the digest against the known correct value. If the implementation is wrong, the device refuses to collect entropy. Passing that test proves the SHA-256 code works — but it says nothing about the Geiger counter, pulse independence or how much minimum entropy actually enters the hash.

The caveat that matters: unvalidated entropy

That last point is the project’s central weakness, and Higgins is unusually candid about it. The entropy source has not been tested under NIST SP 800-90B, the formal framework for validating physical random number generators, and no independent review has established how many bits of genuine unpredictability each pulse comparison contributes. Collecting 512 comparison bits for a maximum 256-bit output is a sensible two-to-one margin, but until the physical source is formally measured, the true entropy content of every generated phrase remains an open question.

The design also omits a secure element and any mechanism proving the installed firmware matches the public repository. A modified unit could display predetermined words or secretly retain generated data while appearing identical to the open-source build — a reminder that physical isolation removes network attack routes, but not supply-chain ones.

Why physical entropy is having a moment

The project lands amid renewed attention on seed-generation security. The past year has seen phishing campaigns target hardware wallet users at scale, including a breach that exposed Trezor customer data, and repeated warnings about weak or reused entropy compromising otherwise air-gapped wallets. Because modern wallets derive every private key from one master seed, weakness in the original entropy propagates to every address the wallet ever creates — there is no partial failure mode.

Dice-based and coin-flip offline generation have long been the purist’s alternative to computer-generated seeds. A Geiger counter is simply the physical entropy tradition taken to its logical extreme: randomness sourced from nuclear physics rather than silicon. For Bitcoin’s security-minded cohort, that appeal is intuitive — atomic decay is about as far from a predictable pseudorandom algorithm as one can get.

Until NIST-style validation and independent hardware review happen, Entropy32 Plus is best understood as a compelling open experiment rather than a production tool. The repository — firmware, circuit boards, fabrication files, enclosures and wordlist — is public for inspection, which is exactly how the project’s own documentation wants it treated.