diff --git a/include/mbedtls/bignum.h b/include/mbedtls/bignum.h
index 3f6cdd1f9..d4aedfc39 100644
--- a/include/mbedtls/bignum.h
+++ b/include/mbedtls/bignum.h
@@ -595,23 +595,22 @@ int mbedtls_mpi_cmp_abs( const mbedtls_mpi *X, const mbedtls_mpi *Y );
 int mbedtls_mpi_cmp_mpi( const mbedtls_mpi *X, const mbedtls_mpi *Y );
 
 /**
- * \brief          Compare two MPIs in constant time.
+ * \brief          Check if an MPI is less than the other in constant time.
  *
  * \param X        The left-hand MPI. This must point to an initialized MPI
  *                 with the same allocated length as Y.
  * \param Y        The right-hand MPI. This must point to an initialized MPI
  *                 with the same allocated length as X.
  * \param ret      The result of the comparison:
- *                 \c 1 if \p X is greater than \p Y.
- *                 \c -1 if \p X is lesser than \p Y.
- *                 \c 0 if \p X is equal to \p Y.
+ *                 \c 1 if \p X is less than \p Y.
+ *                 \c 0 if \p X is greater than or equal to \p Y.
  *
  * \return         0 on success.
  * \return         MBEDTLS_ERR_MPI_BAD_INPUT_DATA if the allocated length of
  *                 the two input MPIs is not the same.
  */
-int mbedtls_mpi_cmp_mpi_ct( const mbedtls_mpi *X, const mbedtls_mpi *Y,
-        int *ret );
+int mbedtls_mpi_lt_mpi_ct( const mbedtls_mpi *X, const mbedtls_mpi *Y,
+        unsigned *ret );
 
 /**
  * \brief          Compare an MPI with an integer.
diff --git a/library/bignum.c b/library/bignum.c
index b90404512..65696470d 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1148,7 +1148,8 @@ int mbedtls_mpi_cmp_mpi( const mbedtls_mpi *X, const mbedtls_mpi *Y )
     return( 0 );
 }
 
-static int ct_lt_mpi_uint( const mbedtls_mpi_uint x, const mbedtls_mpi_uint y )
+static unsigned ct_lt_mpi_uint( const mbedtls_mpi_uint x,
+        const mbedtls_mpi_uint y )
 {
     mbedtls_mpi_uint ret;
     mbedtls_mpi_uint cond;
@@ -1175,16 +1176,11 @@ static int ct_lt_mpi_uint( const mbedtls_mpi_uint x, const mbedtls_mpi_uint y )
     return ret;
 }
 
-static int ct_bool_get_mask( unsigned int b )
-{
-    return ~( b - 1 );
-}
-
 /*
  * Compare signed values in constant time
  */
-int mbedtls_mpi_cmp_mpi_ct( const mbedtls_mpi *X, const mbedtls_mpi *Y,
-        int *ret )
+int mbedtls_mpi_lt_mpi_ct( const mbedtls_mpi *X, const mbedtls_mpi *Y,
+        unsigned *ret )
 {
     size_t i;
     unsigned int cond, done, sign_X, sign_Y;
@@ -1197,45 +1193,49 @@ int mbedtls_mpi_cmp_mpi_ct( const mbedtls_mpi *X, const mbedtls_mpi *Y,
         return MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
 
     /*
-     * if( X->s > 0 && Y->s < 0 )
-     * {
-     *     *ret = 1;
-     *     done = 1;
-     * }
-     * else if( Y->s > 0 && X->s < 0 )
-     * {
-     *     *ret = -1;
-     *     done = 1;
-     * }
+     * Get sign bits of the signs.
      */
     sign_X = X->s;
+    sign_X = sign_X >> ( sizeof( unsigned int ) * 8 - 1 );
     sign_Y = Y->s;
-    cond = ( ( sign_X ^ sign_Y ) >> ( sizeof( unsigned int ) * 8 - 1 ) );
-    *ret = ct_bool_get_mask( cond ) & X->s;
+    sign_Y = sign_Y >> ( sizeof( unsigned int ) * 8 - 1 );
+
+    /*
+     * 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).
+     */
+    cond = ( sign_X ^ sign_Y );
+    *ret = cond & sign_X;
+
+    /*
+     * 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;
 
     for( i = X->n; i > 0; i-- )
     {
         /*
-         * if( ( X->p[i - 1] > Y->p[i - 1] ) && !done )
-         * {
-         *     done = 1;
-         *     *ret = X->s;
-         * }
+         * If Y->p[i - 1] < X->p[i - 1] and both X and Y are negative, then
+         * X < Y.
+         *
+         * Again even if we can make a decision, we just mark the result and
+         * the fact that we are done and continue looping.
          */
-        cond = ct_lt_mpi_uint( Y->p[i - 1], X->p[i - 1] );
-        *ret |= ct_bool_get_mask( cond & ( 1 - done ) ) & X->s;
+        cond = ct_lt_mpi_uint( Y->p[i - 1], X->p[i - 1] ) & sign_X;
+        *ret |= cond & ( 1 - done );
         done |= cond & ( 1 - done );
 
         /*
-         * if( ( X->p[i - 1] < Y->p[i - 1] ) && !done )
-         * {
-         *     done = 1;
-         *     *ret = -X->s;
-         * }
+         * If X->p[i - 1] < Y->p[i - 1] and both X and Y are positive, then
+         * X < Y.
+         *
+         * Again even if we can make a decision, we just mark the result and
+         * the fact that we are done and continue looping.
          */
-        cond = ct_lt_mpi_uint( X->p[i - 1], Y->p[i - 1] );
-        *ret |= ct_bool_get_mask( cond & ( 1 - done ) ) & -X->s;
+        cond = ct_lt_mpi_uint( X->p[i - 1], Y->p[i - 1] ) & ( 1 - sign_X );
+        *ret |= cond & ( 1 - done );
         done |= cond & ( 1 - done );
     }
 
diff --git a/library/ecp.c b/library/ecp.c
index b0ef3ca47..a58e8a6e0 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -2803,7 +2803,7 @@ int mbedtls_ecp_gen_privkey( const mbedtls_ecp_group *grp,
     {
         /* SEC1 3.2.1: Generate d such that 1 <= n < N */
         int count = 0;
-        int cmp = 0;
+        unsigned cmp = 0;
 
         /*
          * Match the procedure given in RFC 6979 (deterministic ECDSA):
@@ -2829,13 +2829,13 @@ int mbedtls_ecp_gen_privkey( const mbedtls_ecp_group *grp,
             if( ++count > 30 )
                 return( MBEDTLS_ERR_ECP_RANDOM_FAILED );
 
-            ret = mbedtls_mpi_cmp_mpi_ct( d, &grp->N, &cmp );
+            ret = mbedtls_mpi_lt_mpi_ct( d, &grp->N, &cmp );
             if( ret != 0 )
             {
                 goto cleanup;
             }
         }
-        while( mbedtls_mpi_cmp_int( d, 1 ) < 0 || cmp >= 0 );
+        while( mbedtls_mpi_cmp_int( d, 1 ) < 0 || cmp != 1 );
     }
 #endif /* ECP_SHORTWEIERSTRASS */
 
diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index efcb06041..89aa4d51f 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -175,38 +175,38 @@ mbedtls_mpi_cmp_mpi:10:"2":10:"-3":1
 Base test mbedtls_mpi_cmp_mpi (Mixed values) #6
 mbedtls_mpi_cmp_mpi:10:"-2":10:"31231231289798":-1
 
-Base test mbedtls_mpi_cmp_mpi_ct #1
-mbedtls_mpi_cmp_mpi_ct:1:10:"693":1:10:"693":0:0
+Base test mbedtls_mpi_lt_mpi_ct #1
+mbedtls_mpi_lt_mpi_ct:1:10:"693":1:10:"693":0:0
 
-Base test mbedtls_mpi_cmp_mpi_ct #2
-mbedtls_mpi_cmp_mpi_ct:1:10:"693":1:10:"692":1:0
+Base test mbedtls_mpi_lt_mpi_ct #2
+mbedtls_mpi_lt_mpi_ct:1:10:"693":1:10:"692":0:0
 
-Base test mbedtls_mpi_cmp_mpi_ct #3
-mbedtls_mpi_cmp_mpi_ct:1:10:"693":1:10:"694":-1:0
+Base test mbedtls_mpi_lt_mpi_ct #3
+mbedtls_mpi_lt_mpi_ct:1:10:"693":1:10:"694":1:0
 
-Base test mbedtls_mpi_cmp_mpi_ct (Negative values) #1
-mbedtls_mpi_cmp_mpi_ct:1:10:"-2":1:10:"-2":0:0
+Base test mbedtls_mpi_lt_mpi_ct (Negative values) #1
+mbedtls_mpi_lt_mpi_ct:1:10:"-2":1:10:"-2":0:0
 
-Base test mbedtls_mpi_cmp_mpi_ct (Negative values) #2
-mbedtls_mpi_cmp_mpi_ct:1:10:"-2":1:10:"-3":1:0
+Base test mbedtls_mpi_lt_mpi_ct (Negative values) #2
+mbedtls_mpi_lt_mpi_ct:1:10:"-2":1:10:"-3":0:0
 
-Base test mbedtls_mpi_cmp_mpi_ct (Negative values) #3
-mbedtls_mpi_cmp_mpi_ct:1:10:"-2":1:10:"-1":-1:0
+Base test mbedtls_mpi_lt_mpi_ct (Negative values) #3
+mbedtls_mpi_lt_mpi_ct:1:10:"-2":1:10:"-1":1:0
 
-Base test mbedtls_mpi_cmp_mpi_ct (Mixed values) #4
-mbedtls_mpi_cmp_mpi_ct:1:10:"-3":1:10:"2":-1:0
+Base test mbedtls_mpi_lt_mpi_ct (Mixed values) #4
+mbedtls_mpi_lt_mpi_ct:1:10:"-3":1:10:"2":1:0
 
-Base test mbedtls_mpi_cmp_mpi_ct (Mixed values) #5
-mbedtls_mpi_cmp_mpi_ct:1:10:"2":1:10:"-3":1:0
+Base test mbedtls_mpi_lt_mpi_ct (Mixed values) #5
+mbedtls_mpi_lt_mpi_ct:1:10:"2":1:10:"-3":0:0
 
-Base test mbedtls_mpi_cmp_mpi_ct (Mixed values) #6
-mbedtls_mpi_cmp_mpi_ct:2:10:"-2":2:10:"31231231289798":-1:0
+Base test mbedtls_mpi_lt_mpi_ct (Mixed values) #6
+mbedtls_mpi_lt_mpi_ct:2:10:"-2":2:10:"31231231289798":1:0
 
-Base test mbedtls_mpi_cmp_mpi_ct (X is longer in storage) #7
-mbedtls_mpi_cmp_mpi_ct:3:10:"693":2:10:"693":0:MBEDTLS_ERR_MPI_BAD_INPUT_DATA
+Base test mbedtls_mpi_lt_mpi_ct (X is longer in storage) #7
+mbedtls_mpi_lt_mpi_ct:3:10:"693":2:10:"693":0:MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
-Base test mbedtls_mpi_cmp_mpi_ct (Y is longer in storage) #8
-mbedtls_mpi_cmp_mpi_ct:3:10:"693":4:10:"693":0:MBEDTLS_ERR_MPI_BAD_INPUT_DATA
+Base test mbedtls_mpi_lt_mpi_ct (Y is longer in storage) #8
+mbedtls_mpi_lt_mpi_ct:3:10:"693":4:10:"693":0:MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
 Base test mbedtls_mpi_cmp_abs #1
 mbedtls_mpi_cmp_abs:10:"693":10:"693":0
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 97fd7b983..617f4615c 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -588,10 +588,12 @@ exit:
 /* END_CASE */
 
 /* BEGIN_CASE */
-void mbedtls_mpi_cmp_mpi_ct( int size_X, int radix_X, char * input_X, int size_Y,
-                             int radix_Y, char * input_Y, int input_ret, int input_err )
+void mbedtls_mpi_lt_mpi_ct( int size_X, int radix_X, char * input_X,
+                            int size_Y, int radix_Y, char * input_Y,
+                            int input_ret, int input_err )
 {
-    int ret;
+    unsigned ret;
+    unsigned input_uret = input_ret;
     mbedtls_mpi X, Y;
     mbedtls_mpi_init( &X ); mbedtls_mpi_init( &Y );
 
@@ -601,9 +603,9 @@ void mbedtls_mpi_cmp_mpi_ct( int size_X, int radix_X, char * input_X, int size_Y
     mbedtls_mpi_grow( &X, size_X );
     mbedtls_mpi_grow( &Y, size_Y );
 
-    TEST_ASSERT( mbedtls_mpi_cmp_mpi_ct( &X, &Y, &ret ) == input_err );
+    TEST_ASSERT( mbedtls_mpi_lt_mpi_ct( &X, &Y, &ret ) == input_err );
     if( input_err == 0 )
-        TEST_ASSERT( ret == input_ret );
+        TEST_ASSERT( ret == input_uret );
 
 exit:
     mbedtls_mpi_free( &X ); mbedtls_mpi_free( &Y );