| /** |
| * Constant-time functions |
| */ |
| /* |
| * Copyright The Mbed TLS Contributors |
| * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later |
| */ |
| |
| #ifndef MBEDTLS_CONSTANT_TIME_H |
| #define MBEDTLS_CONSTANT_TIME_H |
| |
| #include <stddef.h> |
| |
| /** Constant-time buffer comparison without branches. |
| * |
| * This is equivalent to the standard memcmp function, but is likely to be |
| * compiled to code using bitwise operations 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, 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 contents of the two buffers are the same, |
| * otherwise non-zero. |
| */ |
| int mbedtls_ct_memcmp(const void *a, |
| const void *b, |
| size_t n); |
| |
| #endif /* MBEDTLS_CONSTANT_TIME_H */ |