CryptoUtils.h File Reference

Detailed Description

A collection of utility functions for cryptographic purposes.

============================================================================

#include <stdint.h>
#include <stdbool.h>
#include <string.h>

Include dependency graph for CryptoUtils.h:

Go to the source code of this file.

Functions
bool	CryptoUtils_buffersMatch (const volatile void *volatile buffer0, const volatile void *volatile buffer1, size_t bufferByteLength)
	Compares two buffers for equality without branching. More...
bool	CryptoUtils_buffersMatchWordAligned (const volatile uint32_t *volatile buffer0, const volatile uint32_t *volatile buffer1, size_t bufferByteLength)
	Compares two buffers for equality word-by-word without branching. More...
bool	CryptoUtils_isBufferAllZeros (const void *buffer, size_t bufferByteLength)
	Check whether the provided buffer only contains 0x00 bytes. More...
void	CryptoUtils_memset (void *dest, size_t destSize, uint8_t val, size_t count)
	Copies val into the first count bytes of the buffer pointed to by dest. More...
void	CryptoUtils_reverseBufferBytewise (void *buffer, size_t bufferByteLength)
	Reverses the byte order in a buffer of a given length. More...
void	CryptoUtils_copyPad (const void *source, uint32_t *destination, size_t sourceLength)
	Copies and pads an array of words. More...
void	CryptoUtils_reverseCopyPad (const void *source, uint32_t *destination, size_t sourceLength)
	Reverses, copies, and pads an array of words. More...
void	CryptoUtils_reverseCopy (const void *source, void *destination, size_t sourceLength)
	Reverses and copies an array of bytes. More...

Function Documentation

CryptoUtils_buffersMatch()

bool CryptoUtils_buffersMatch	(	const volatile void *volatile	buffer0,
		const volatile void *volatile	buffer1,
		size_t	bufferByteLength
	)

Compares two buffers for equality without branching.

Note

This is not a drop-in replacement for memcmp!

Most memcmp implementations break out of their comparison loop immediately once a mismatch is detected to save execution time. For cryptographic purposes, this is a flaw.

This function compares two buffers without branching thus requiring a an amount of time that does not vary with the content of buffer0 and buffer1.

Parameters

buffer0	Buffer to compare against buffer1.
buffer1	Buffer tp compare against buffer0
bufferByteLength	Length in bytes of buffer0 and buffer1.

Return values

true	The contents of the buffers match.
false	The contents of the buffers do not match.

CryptoUtils_buffersMatchWordAligned()

bool CryptoUtils_buffersMatchWordAligned	(	const volatile uint32_t *volatile	buffer0,
		const volatile uint32_t *volatile	buffer1,
		size_t	bufferByteLength
	)

Compares two buffers for equality word-by-word without branching.

Note

This is not a drop-in replacement for memcmp!

Most memcmp implementations break out of their comparison loop immediately once a mismatch is detected to save execution time. For cryptographic purposes, this is a flaw.

This function compares two buffers without branching thus requiring a an amount of time that does not vary with the content of buffer0 and buffer1.

Unlike CryptoUtils_buffersMatch(), this function expects buffer0 and buffer1 to be 32-bit aligned. It will only perform 32-bit aligned accesses to memory. This is needed to access the registers of certain peripherals.

Parameters

buffer0	Buffer to compare against buffer1.
buffer1	Buffer tp compare against buffer0
bufferByteLength	Length in bytes of buffer0 and buffer1. Must be evenly divisible by sizeof(uint32_t). This function will return false if bufferByteLength is not evenly divisible by sizeof(uin32_t).

Return values

true	The contents of the buffers match.
false	The contents of the buffers do not match.

CryptoUtils_isBufferAllZeros()

bool CryptoUtils_isBufferAllZeros	(	const void *	buffer,
		size_t	bufferByteLength
	)

Check whether the provided buffer only contains 0x00 bytes.

Parameters

buffer	Buffer to search for non-zero bytes
bufferByteLength	Length of buffer in bytes

Return values

true	The buffer contained only bytes with value 0x00
false	The buffer contained at least on non-zero byte

CryptoUtils_memset()

void CryptoUtils_memset	(	void *	dest,
		size_t	destSize,
		uint8_t	val,
		size_t	count
	)

Copies val into the first count bytes of the buffer pointed to by dest.

Parameters

dest	Pointer to destination buffer
destSize	Size of destination buffer in bytes
val	Fill byte value
count	Number of bytes to fill

CryptoUtils_reverseBufferBytewise()

void CryptoUtils_reverseBufferBytewise	(	void *	buffer,
		size_t	bufferByteLength
	)

Reverses the byte order in a buffer of a given length.

The left-most byte will become the right-most byte and vice versa.

Parameters

buffer	Buffer containing the data to be reversed.
bufferByteLength	Length in bytes of buffer.

CryptoUtils_copyPad()

void CryptoUtils_copyPad	(	const void *	source,
		uint32_t *	destination,
		size_t	sourceLength
	)

Copies and pads an array of words.

The source array is copied into the destination array. Writes are done word-wise. If sourceLength is not a multiple of 4, any remaining bytes up to the next word boundary are padded with 0.

The length of the destination array must be a multiple of 4, rounded up to the padded sourceLength if required.

Parameters

source	Source array
destination	Destination array
sourceLength	Length of the source array

CryptoUtils_reverseCopyPad()

void CryptoUtils_reverseCopyPad	(	const void *	source,
		uint32_t *	destination,
		size_t	sourceLength
	)

Reverses, copies, and pads an array of words.

The source array is reversed byte-wise and copied into the destination array. Writes are done word-wise. If sourceLength is not a multiple of 4, any remaining bytes up to the next word boundary are padded with 0.

The length of the destination array must be a multiple of 4, rounded up to the padded sourceLength if required.

Parameters

source	Source array
destination	Destination array
sourceLength	Length of the source array

CryptoUtils_reverseCopy()

void CryptoUtils_reverseCopy	(	const void *	source,
		void *	destination,
		size_t	sourceLength
	)

Reverses and copies an array of bytes.

The source array is reversed byte-wise and copied into the destination array.

Parameters

source	Source array
destination	Destination array
sourceLength	Length of the source array