From cf7eeef2ccfce13eeb184b25624e2fb6dc0b0661 Mon Sep 17 00:00:00 2001
From: Janos Follath <janos.follath@arm.com>
Date: Mon, 28 Oct 2019 12:23:18 +0000
Subject: [PATCH] mbedtls_mpi_lt_mpi_ct: Improve documentation
---
library/bignum.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/library/bignum.c b/library/bignum.c
index c1bed6642..3328d64e6 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1113,6 +1113,7 @@ 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 );
@@ -1131,14 +1132,14 @@ 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;