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Improve docs for mbedtls_ct_memcmp

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
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Dave Rodgman 2023-07-31 12:33:47 +01:00
parent 9ee0e1f6fe
commit ad9e5b9abe
1 changed files with 8 additions and 5 deletions
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13
include/mbedtls/constant_time.h
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@ -26,16 +26,19 @@
/** Constant-time buffer comparison without branches.
*
* This is equivalent to the standard memcmp function, but is likely to be
* compiled to code using bitwise operation rather than a branch.
* compiled to code using bitwise operation rather than a branch, such that
* the time taken is constant w.r.t. the data pointed to by \p a and \p b,
* and w.r.t. whether \p a and \p b are equal or not. It is not constant-time
* w.r.t. \p n .
*
* This function can be used to write constant-time code by replacing branches
* with bit operations using masks.
*
* \param a Pointer to the first buffer.
* \param b Pointer to the second buffer.
* \param n The number of bytes to compare in the buffer.
* \param a Pointer to the first buffer, containing at least \p n bytes. May not be NULL.
* \param b Pointer to the second buffer, containing at least \p n bytes. May not be NULL.
* \param n The number of bytes to compare.
*
* \return Zero if the content of the two buffer is the same,
* \return Zero if the contents of the two buffers are the same,
* otherwise non-zero.
*/
int mbedtls_ct_memcmp(const void *a,