Copyright Sabin Padurariu (c) 2025

Random Number Generator

General Overview

Random Number Generator (TRNG) designed for microcontroller-based systems. Unlike pseudo-random number generators (PRNGs), which rely on deterministic algorithms and seed values, this TRNG uses hardware-based entropy sources to produce non-deterministic, unpredictable random numbers, ideal for cryptographic applications, secure communications, and authentication systems.

Getting Started

Compile the sources using make.

make

Load the generated ".hex" file into the avr using avrdude utility.

make upload

Functionality

The microcontroller gets the values from three main sources.

Peripheral sources:

• entropy sampler circuit
• temperature sensor
• proximity sensor

It receives the values from the sources and applies a fast hashing algorithm to compute the final random number.

The number is transmitted to the user over bluetooth.

Peripherals and Pins

The peripherals use all built-in timers:

• timer0 - 8-bit
• timer1 - 16-bit
• timer2 - 8-bit

Temperature Sensor

The DHT11 is a digital temperature and humidity sensor that communicates with the microcontroller via a single-wire serial protocol. It has strict timing requirements for initiating communication and receiving data.

The value from the temperature sensor is read by the ADC using timer0.

Distance Sensor

The HC-SR04 ultrasonic sensor measures distance by emitting an ultrasonic pulse and timing its echo. Accurate time measurement in microseconds is critical for calculating distance.

The value from the ECHO pin is read using timer1.

Sampler Circuit

The sampler circuit uses the noise from the junction of a BJT transistor to produce random bits. The noise is amplified and sent to the ADC of the microcontroller.

The value from the sampler circuit is read by the ADC using timer2.