trng.c File Reference

Implementation of the True Random Number Generator (TRNG) functions. More...

#include "trng.h"

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Functions
void	trng_init (void)
	Initializes the True Random Number Generator (TRNG) module.
void	trng_next_bit (unsigned char bit)
	Processes a single entropy bit and adds it to the TRNG buffer.
TRNG_Buffer	trng_buffer_status (void)
	Returns the current fill status of the TRNG buffer.
volatile unsigned char *	trng_buffer (void)
	Returns a pointer to the internal TRNG buffer.
void	trng_reset (void)
	Returns a pointer to the internal TRNG buffer.

Variables
volatile unsigned char	buffer [10UL]
volatile unsigned char	current_buffer_position
volatile unsigned char	current_buffer_bit_position
volatile unsigned char	first_bit
volatile unsigned char	last_bit
volatile unsigned char	primary_run

Detailed Description

Implementation of the True Random Number Generator (TRNG) functions.

This file contains the implementation of the TRNG driver functions used to initialize, reset, and manage a True Random Number Generator. It processes entropy bits using a Von Neumann correction algorithm and stores the resulting random data in an internal buffer for later retrieval.

The library is intended for embedded systems requiring nondeterministic random data, such as cryptographic applications, seeding pseudorandom generators, or generating unique identifiers.

Author

g.raf

Date

2026-01-27

Version

1.0 Release

Copyright

Copyright (c) 2026 g.raf Released under the GPLv3 License. (see LICENSE in repository)

Note

This file is part of a larger embedded project and is subject to the license specified in the repository. For updates and the complete revision history, see the project's GitHub repository.

See also

https://github.com/0x007e/drivers-crypto-trng "TRNG driver library"

Function Documentation

trng_buffer()

volatile unsigned char * trng_buffer

(

void

)

Returns a pointer to the internal TRNG buffer.

This function provides direct access to the internal memory buffer that stores the corrected random bytes generated by the True Random Number Generator (TRNG). The buffer can be read once the buffer status, retrieved by trng_buffer_status(), indicates that it is full.

Returns

volatile unsigned char*: Pointer to the internal TRNG buffer containing random data.

Note

• The returned pointer references volatile memory, as the buffer content may be modified by ongoing TRNG operations.
• Ensure that the buffer is not read while still filling to avoid inconsistent data.

See also

trng_buffer_status(), trng_reset()

trng_buffer_status()

TRNG_Buffer trng_buffer_status

(

void

)

Returns the current fill status of the TRNG buffer.

This function checks the internal TRNG buffer and reports whether it is empty, partially filled, or completely full. It uses internal position counters to determine the current state of the random data storage.

The return value can be one of the following:

• TRNG_Buffer_Empty — no random bits have been stored yet
• TRNG_Buffer_Filling — the buffer is currently being filled
• TRNG_Buffer_Full — the buffer is full and ready for readout or reset

Returns

TRNG_Buffer: The current buffer status as a value from the TRNG_Buffer enumeration.

Note

This function allows external code to determine when new random data can be read or when the buffer should be reset.

See also

trng_buffer(), trng_reset(), trng_next_bit()

trng_init()

void trng_init

(

void

)

Initializes the True Random Number Generator (TRNG) module.

This function prepares the TRNG module for operation by resetting its internal state and buffer. It should be called once during system initialization before feeding entropy bits using trng_next_bit(). Internally, this function calls trng_reset() to clear all buffer data and reset counters.

Note

Must be called before any random data collection begins.

See also

trng_reset(), trng_next_bit(), trng_buffer_status()

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trng_next_bit()

void trng_next_bit

(

unsigned char

bit

)

Processes a single entropy bit and adds it to the TRNG buffer.

This function is called repeatedly with raw entropy bits obtained from a hardware or software noise source. It applies the Von Neumann correction algorithm to remove bias from the input bit sequence and produces unbiased random bits. The corrected bits are packed into the internal TRNG buffer until it reaches the configured size defined by TRNG_BUFFER_SIZE. Once the buffer is full, no further bits are stored until it is reset.

Parameters

bit	The next raw entropy bit to process (must be 0 or 1).

Note

• The function performs no operation if the buffer is already full.
• Each call expects a single bit input, not a byte or word.
• This function internally manages bit-packing and buffer indexing.

See also

trng_init(), trng_reset(), trng_buffer(), trng_buffer_status()

trng_reset()

void trng_reset

(

void

)

Returns a pointer to the internal TRNG buffer.

This function provides direct access to the internal memory buffer that stores the corrected random bytes generated by the True Random Number Generator (TRNG). The buffer can be read once the buffer status, retrieved by trng_buffer_status(), indicates that it is full.

Returns

volatile unsigned char*: Pointer to the internal TRNG buffer containing random data.

Note

• The returned pointer references volatile memory, as the buffer content may be modified by ongoing TRNG operations.
• Ensure that the buffer is not read while still filling to avoid inconsistent data.

See also

trng_buffer_status(), trng_reset()

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Variable Documentation

buffer

volatile unsigned char buffer[10UL]

current_buffer_bit_position

volatile unsigned char current_buffer_bit_position

current_buffer_position

volatile unsigned char current_buffer_position

first_bit

volatile unsigned char first_bit

last_bit

volatile unsigned char last_bit

primary_run

volatile unsigned char primary_run