mbedtls_ct_memcmp() function

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.