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Araneus Alea II

True Random Number Generator

The Alea II has been discontinued. The information on this page is for reference only.

The Alea II is a compact true random number generator (TRNG), also known as a hardware random number generator (HWRNG), non-deterministic random bit generator (NRBG), or entropy source, with a USB interface.

The Alea II is based on the proven technology of our Alea I TRNG and is fully compatible with existing Alea I drivers and applications. By using smaller surface-mount components, we have been able to fit the same functionality in a smaller package, add a bi-color status LED, and reduce the cost.

The Alea II is designed for demanding cryptographic applications such as key generation, DSA signature generation, cryptographic nonces, and one time pads. It can also be used in a number of other applications such as lotteries, games, Monte Carlo simulations, and random sampling for scientific studies.


The Alea II provides a stream of high quality random bits that passes a number of stringent statistical tests including the Diehard and NIST STS test suites. We also test the output of every Alea II for uniqueness using the Known Number Oracle.

You can download random data produced by an Alea II TRNG here, for example to run your own statistical tests.


The Alea II plugs directly into, and is powered by, the USB port — no cable or external power supply is needed.


The Alea II comes with driver support for Microsoft Windows versions from XP through 10, and an ActiveX control that enables access to the device through COM. Recent versions of Linux, NetBSD, and OpenBSD include drivers that support the Alea II as an entropy source for the kernel entropy pool. Applications can also read random bits directly from the Alea II using the libusb library on Linux, NetBSD, OpenBSD, FreeBSD, and macOS systems. The USB protocol of the Alea II is documented, allowing users to write their own drivers if desired.

How it Works

The Alea II uses a reverse biased semiconductor junction to generate wide-band Gaussian white noise. This noise is amplified and digitized using an analog-to-digital converter. The raw output bits from the A/D converter are then further processed by an embedded microprocessor to combine the entropy from multiple samples into each final output bit, resulting in a random bit stream that is practically free from bias and correlation.

Technical specifications

Random data rate: 100 kilobits / second typ.
Interface: Full speed USB
Power consumption: less than 250 mW
Dimensions: 59 x 21 x 12 mm including the USB connector
Specifications are subject to change without notice.