hardened_memory.h File Reference

Hardened memory operations for constant power buffer manipulation. More...

#include <stddef.h>
#include <stdint.h>
#include "sw/device/lib/base/hardened.h"
#include "sw/device/lib/base/macros.h"

Go to the source code of this file.

Functions
uint32_t	hardened_memshred_random_word (void)
	Expects some external implementation of randomness to be linked.
void	hardened_memcpy (uint32_t *OT_RESTRICT dest, const uint32_t *OT_RESTRICT src, size_t word_len)
	Copies 32-bit words between non-overlapping regions.
void	hardened_memshred (uint32_t *dest, size_t word_len)
	Fills a 32-bit aligned region of memory with random data.
hardened_bool_t	hardened_memeq (const uint32_t *lhs, const uint32_t *rhs, size_t word_len)
	Compare two potentially-overlapping 32-bit aligned regions of memory for equality.
void	hardened_xor (uint32_t *OT_RESTRICT x, const uint32_t *OT_RESTRICT y, size_t word_len)
	Combines two word buffers with XOR.

Detailed Description

Hardened memory operations for constant power buffer manipulation.

Definition in file hardened_memory.h.

Function Documentation

hardened_memcpy()

void hardened_memcpy	(	uint32_t *OT_RESTRICT	dest,
		const uint32_t *OT_RESTRICT	src,
		size_t	word_len )

Copies 32-bit words between non-overlapping regions.

Unlike memcpy(), this function has important differences:

• It is significantly slower, since it mitigates power-analysis attacks.
• It performs operations on 32-bit words, rather than bytes.
• It returns void.

Input pointers MUST be 32-bit aligned, although they do not need to actually point to memory declared as uint32_t per the C aliasing rules. Internally, this function is careful to not dereference its operands directly, and instead uses dedicated load/store intrinsics.

Parameters

dest	The destination of the copy.
src	The source of the copy.
word_len	The number of words to copy.

hardened_memeq()

hardened_bool_t hardened_memeq	(	const uint32_t *	lhs,
		const uint32_t *	rhs,
		size_t	word_len )

Compare two potentially-overlapping 32-bit aligned regions of memory for equality.

Unlike memcmp(), this function has important differences:

• It is significantly slower, since it mitigates power-analysis attacks.
• It performs operations on 32-bit words, rather than bytes.
• It only computes equality, not lexicographic ordering, which would be even slower.
• It returns a hardened_bool_t.
• It is constant-time.

Input pointers MUST be 32-bit aligned, although they do not need to actually point to memory declared as uint32_t per the C aliasing rules. Internally, this function is careful to not dereference its operands directly, and instead uses dedicated load/store intrinsics.

Parameters

lhs	The first buffer to compare.
rhs	The second buffer to compare.
word_len	The number of words to write.

Definition at line 113 of file hardened_memory.c.

hardened_memshred()

void hardened_memshred	(	uint32_t *	dest,
		size_t	word_len )

Fills a 32-bit aligned region of memory with random data.

Unlike memset(), this function has important differences:

• It is significantly slower, since it mitigates power-analysis attacks.
• It performs operations on 32-bit words, rather than bytes.
• A fill value cannot be specified.
• It returns void.

Input pointers MUST be 32-bit aligned, although they do not need to actually point to memory declared as uint32_t per the C aliasing rules. Internally, this function is careful to not dereference its operands directly, and instead uses dedicated load/store intrinsics.

Parameters

dest	The destination of the set.
word_len	The number of words to write.

Definition at line 82 of file hardened_memory.c.

hardened_memshred_random_word()

uint32_t hardened_memshred_random_word ( void )

extern

Expects some external implementation of randomness to be linked.

Returns

A fresh random word.

hardened_xor()

void hardened_xor	(	uint32_t *OT_RESTRICT	x,
		const uint32_t *OT_RESTRICT	y,
		size_t	word_len )

Combines two word buffers with XOR.

Callers should ensure the entropy complex is up before calling this function. The implementation uses random-order hardening primitives for side-channel defense.

Parameters

[in,out]	x	Pointer to the first operand (modified in-place).
	y	Pointer to the second operand.
	word_len	Length in words of each operand.