128 RNG
128 : RNG
- Author: Felix N
- Description: Ring oscillator based random number generator
- GitHub repository
- Open in 3D viewer
- Clock: 500000 Hz
How it works
This project is a true random number generator.
The core of the TRNG is a set of three ring oscillators of different lengths (6, 12, and 24 inverters). These oscillators produce unstable, jittery signals. The outputs are combined using an XOR gate to create a chaotic bit stream. Here is the ring oscillator frequency estimates:
| Ring Oscillator | Frequency Estimate | Period Estimate |
|---|---|---|
| 6 | ~231 MHz | 4.32 ns |
| 12 | ~117 MHz | 8.52 ns |
| 24 | ~59 MHz | 16.91 ns |
The raw random bitstream may have a bias (more 1s than 0s). To correct this, a Von Neumann corrector is used. It takes pairs of bits from the stream:
- If the bits are 01, it outputs a 0.
- If the bits are 10, it outputs a 1.
If the bits are the same (00 or 11), it outputs nothing.
The debiased bits are collected one by one and shifted into a 32-bit register. Once a 32 bit number has been collected, it is output through the UART.
How to test
To test the design, you will need to monitor the UART output. Connect a UART-to-USB adapter to the uo_out[0] pin (which is the UART TX pin), the ground pin, and the power pin of your board.
Configure the serial terminal to match the UART settings: Baud Rate: 9600 Data Bits: 8 Parity: None Stop Bits: 1
Once connected, you should see a continuous stream of raw binary data appearing in your terminal. This is the 32-bit random numbers being sent from the chip.
The raw ring oscillator outputs can also be monitored on the uo_out[1], uo_out[2], and uo_out[3] pins, which correspond to the 6, 12, and 24 inverter ring oscillators respectively.
External hardware
A UART-to-USB adapter is required to connect the chip's output to a computer and view the generated random numbers.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | Uart TX | ||
| 1 | ring oscillator 6 | ||
| 2 | ring oscillator 12 | ||
| 3 | ring oscillator 24 | ||
| 4 | |||
| 5 | |||
| 6 | |||
| 7 |