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mbedtls_mpi_lt_mpi_ct: Improve documentation

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This commit is contained in:
Janos Follath 2019-10-28 12:23:18 +00:00
parent 73ba9ec9a6
commit bb5147f165
1 changed files with 4 additions and 3 deletions
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7
library/bignum.c
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@ -1190,6 +1190,7 @@ int mbedtls_mpi_lt_mpi_ct( const mbedtls_mpi *X, const mbedtls_mpi *Y,
unsigned *ret )
{
size_t i;
/* The value of any of these variables is either 0 or 1 at all times. */
unsigned cond, done, sign_X, sign_Y;
MPI_VALIDATE_RET( X != NULL );
@ -1208,14 +1209,14 @@ int mbedtls_mpi_lt_mpi_ct( const mbedtls_mpi *X, const mbedtls_mpi *Y,
/*
* If the signs are different, then the positive operand is the bigger.
* That is if X is negative (sign bit 1), then X < Y is true and it is false
* if X is positive (sign bit 0).
* That is if X is negative (sign_X == 1), then X < Y is true and it is
* false if X is positive (sign_X == 0).
*/
cond = ( sign_X ^ sign_Y );
*ret = cond & sign_X;
/*
* This is a constant time function, we might have the result, but we still
* This is a constant-time function. We might have the result, but we still
* need to go through the loop. Record if we have the result already.
*/
done = cond;