diff --git a/library/bignum_core.c b/library/bignum_core.c
index d0728e7..89fd404 100644
--- a/library/bignum_core.c
+++ b/library/bignum_core.c
@@ -25,6 +25,7 @@
 
 #include "mbedtls/error.h"
 #include "mbedtls/platform_util.h"
+#include "constant_time_internal.h"
 
 #include "mbedtls/platform.h"
 
@@ -153,6 +154,36 @@
     }
 }
 
+void mbedtls_mpi_core_cond_assign( mbedtls_mpi_uint *X,
+                                   const mbedtls_mpi_uint *A,
+                                   size_t limbs,
+                                   unsigned char assign )
+{
+    if( X == A )
+        return;
+
+    mbedtls_ct_mpi_uint_cond_assign( limbs, X, A, assign );
+}
+
+void mbedtls_mpi_core_cond_swap( mbedtls_mpi_uint *X,
+                                 mbedtls_mpi_uint *Y,
+                                 size_t limbs,
+                                 unsigned char swap )
+{
+    if( X == Y )
+        return;
+
+    /* all-bits 1 if swap is 1, all-bits 0 if swap is 0 */
+    mbedtls_mpi_uint limb_mask = mbedtls_ct_mpi_uint_mask( swap );
+
+    for( size_t i = 0; i < limbs; i++ )
+    {
+        mbedtls_mpi_uint tmp = X[i];
+        X[i] = ( X[i] & ~limb_mask ) | ( Y[i] & limb_mask );
+        Y[i] = ( Y[i] & ~limb_mask ) | (  tmp & limb_mask );
+    }
+}
+
 int mbedtls_mpi_core_read_le( mbedtls_mpi_uint *X,
                               size_t X_limbs,
                               const unsigned char *input,
diff --git a/library/bignum_core.h b/library/bignum_core.h
index 8e227f8..b626fab 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -74,6 +74,58 @@
 void mbedtls_mpi_core_bigendian_to_host( mbedtls_mpi_uint *A,
                                          size_t A_limbs );
 
+/**
+ * \brief   Perform a safe conditional copy of an MPI which doesn't reveal
+ *          whether assignment was done or not.
+ *
+ * \param[out] X        The address of the destination MPI.
+ *                      This must be initialized. Must have enough limbs to
+ *                      store the full value of \p A.
+ * \param[in]  A        The address of the source MPI. This must be initialized.
+ * \param      limbs    The number of limbs of \p A.
+ * \param      assign   The condition deciding whether to perform the
+ *                      assignment or not. Must be either 0 or 1:
+ *                      * \c 1: Perform the assignment `X = A`.
+ *                      * \c 0: Keep the original value of \p X.
+ *
+ * \note           This function avoids leaking any information about whether
+ *                 the assignment was done or not.
+ *
+ * \warning        If \p assign is neither 0 nor 1, the result of this function
+ *                 is indeterminate, and the resulting value in \p X might be
+ *                 neither its original value nor the value in \p A.
+ */
+void mbedtls_mpi_core_cond_assign( mbedtls_mpi_uint *X,
+                                   const mbedtls_mpi_uint *A,
+                                   size_t limbs,
+                                   unsigned char assign );
+
+/**
+ * \brief   Perform a safe conditional swap of two MPIs which doesn't reveal
+ *          whether the swap was done or not.
+ *
+ * \param[in,out] X         The address of the first MPI.
+ *                          This must be initialized.
+ * \param[in,out] Y         The address of the second MPI.
+ *                          This must be initialized.
+ * \param         limbs     The number of limbs of \p X and \p Y.
+ * \param         swap      The condition deciding whether to perform
+ *                          the swap or not. Must be either 0 or 1:
+ *                          * \c 1: Swap the values of \p X and \p Y.
+ *                          * \c 0: Keep the original values of \p X and \p Y.
+ *
+ * \note           This function avoids leaking any information about whether
+ *                 the swap was done or not.
+ *
+ * \warning        If \p swap is neither 0 nor 1, the result of this function
+ *                 is indeterminate, and both \p X and \p Y might end up with
+ *                 values different to either of the original ones.
+ */
+void mbedtls_mpi_core_cond_swap( mbedtls_mpi_uint *X,
+                                 mbedtls_mpi_uint *Y,
+                                 size_t limbs,
+                                 unsigned char swap );
+
 /** Import X from unsigned binary data, little-endian.
  *
  * The MPI needs to have enough limbs to store the full value (including any
diff --git a/library/bignum_mod_raw.c b/library/bignum_mod_raw.c
index e1c96d6..4b8a698 100644
--- a/library/bignum_mod_raw.c
+++ b/library/bignum_mod_raw.c
@@ -33,6 +33,22 @@
 #include "bignum_mod.h"
 #include "constant_time_internal.h"
 
+void mbedtls_mpi_mod_raw_cond_assign( mbedtls_mpi_uint *X,
+                                      const mbedtls_mpi_uint *A,
+                                      const mbedtls_mpi_mod_modulus *N,
+                                      unsigned char assign )
+{
+    mbedtls_mpi_core_cond_assign( X, A, N->limbs, assign );
+}
+
+void mbedtls_mpi_mod_raw_cond_swap( mbedtls_mpi_uint *X,
+                                    mbedtls_mpi_uint *Y,
+                                    const mbedtls_mpi_mod_modulus *N,
+                                    unsigned char swap )
+{
+    mbedtls_mpi_core_cond_swap( X, Y, N->limbs, swap );
+}
+
 int mbedtls_mpi_mod_raw_read( mbedtls_mpi_uint *X,
                               const mbedtls_mpi_mod_modulus *m,
                               const unsigned char *input,
diff --git a/library/bignum_mod_raw.h b/library/bignum_mod_raw.h
index 7b3a0c1..f698a9a 100644
--- a/library/bignum_mod_raw.h
+++ b/library/bignum_mod_raw.h
@@ -33,6 +33,60 @@
 
 #include "bignum_mod.h"
 
+/**
+ * \brief   Perform a safe conditional copy of an MPI which doesn't reveal
+ *          whether the assignment was done or not.
+ *
+ * The size to copy is determined by \p N.
+ *
+ * \param[out] X        The address of the destination MPI.
+ *                      This must be initialized. Must have enough limbs to
+ *                      store the full value of \p A.
+ * \param[in]  A        The address of the source MPI. This must be initialized.
+ * \param[in]  N        The address of the modulus related to \p X and \p A.
+ * \param      assign   The condition deciding whether to perform the
+ *                      assignment or not. Must be either 0 or 1:
+ *                      * \c 1: Perform the assignment `X = A`.
+ *                      * \c 0: Keep the original value of \p X.
+ *
+ * \note           This function avoids leaking any information about whether
+ *                 the assignment was done or not.
+ *
+ * \warning        If \p assign is neither 0 nor 1, the result of this function
+ *                 is indeterminate, and the resulting value in \p X might be
+ *                 neither its original value nor the value in \p A.
+ */
+void mbedtls_mpi_mod_raw_cond_assign( mbedtls_mpi_uint *X,
+                                      const mbedtls_mpi_uint *A,
+                                      const mbedtls_mpi_mod_modulus *N,
+                                      unsigned char assign );
+
+/**
+ * \brief   Perform a safe conditional swap of two MPIs which doesn't reveal
+ *          whether the swap was done or not.
+ *
+ * The size to swap is determined by \p N.
+ *
+ * \param[in,out] X     The address of the first MPI. This must be initialized.
+ * \param[in,out] Y     The address of the second MPI. This must be initialized.
+ * \param[in]     N     The address of the modulus related to \p X and \p Y.
+ * \param         swap  The condition deciding whether to perform
+ *                      the swap or not. Must be either 0 or 1:
+ *                      * \c 1: Swap the values of \p X and \p Y.
+ *                      * \c 0: Keep the original values of \p X and \p Y.
+ *
+ * \note           This function avoids leaking any information about whether
+ *                 the swap was done or not.
+ *
+ * \warning        If \p swap is neither 0 nor 1, the result of this function
+ *                 is indeterminate, and both \p X and \p Y might end up with
+ *                 values different to either of the original ones.
+ */
+void mbedtls_mpi_mod_raw_cond_swap( mbedtls_mpi_uint *X,
+                                    mbedtls_mpi_uint *Y,
+                                    const mbedtls_mpi_mod_modulus *N,
+                                    unsigned char swap );
+
 /** Import X from unsigned binary data.
  *
  * The MPI needs to have enough limbs to store the full value (including any
diff --git a/library/constant_time.c b/library/constant_time.c
index 01a6976..510304e 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -30,6 +30,7 @@
 
 #if defined(MBEDTLS_BIGNUM_C)
 #include "mbedtls/bignum.h"
+#include "bignum_core.h"
 #endif
 
 #if defined(MBEDTLS_SSL_TLS_C)
@@ -678,21 +679,19 @@
                                   unsigned char assign )
 {
     int ret = 0;
-    size_t i;
-    mbedtls_mpi_uint limb_mask;
     MPI_VALIDATE_RET( X != NULL );
     MPI_VALIDATE_RET( Y != NULL );
 
     /* all-bits 1 if assign is 1, all-bits 0 if assign is 0 */
-    limb_mask = mbedtls_ct_mpi_uint_mask( assign );;
+    mbedtls_mpi_uint limb_mask = mbedtls_ct_mpi_uint_mask( assign );
 
     MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, Y->n ) );
 
     X->s = mbedtls_ct_cond_select_sign( assign, Y->s, X->s );
 
-    mbedtls_ct_mpi_uint_cond_assign( Y->n, X->p, Y->p, assign );
+    mbedtls_mpi_core_cond_assign( X->p, Y->p, Y->n, assign );
 
-    for( i = Y->n; i < X->n; i++ )
+    for( size_t i = Y->n; i < X->n; i++ )
         X->p[i] &= ~limb_mask;
 
 cleanup:
@@ -709,19 +708,14 @@
                                 mbedtls_mpi *Y,
                                 unsigned char swap )
 {
-    int ret, s;
-    size_t i;
-    mbedtls_mpi_uint limb_mask;
-    mbedtls_mpi_uint tmp;
+    int ret = 0;
+    int s;
     MPI_VALIDATE_RET( X != NULL );
     MPI_VALIDATE_RET( Y != NULL );
 
     if( X == Y )
         return( 0 );
 
-    /* all-bits 1 if swap is 1, all-bits 0 if swap is 0 */
-    limb_mask = mbedtls_ct_mpi_uint_mask( swap );
-
     MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, Y->n ) );
     MBEDTLS_MPI_CHK( mbedtls_mpi_grow( Y, X->n ) );
 
@@ -729,13 +723,7 @@
     X->s = mbedtls_ct_cond_select_sign( swap, Y->s, X->s );
     Y->s = mbedtls_ct_cond_select_sign( swap, s, Y->s );
 
-
-    for( i = 0; i < X->n; i++ )
-    {
-        tmp = X->p[i];
-        X->p[i] = ( X->p[i] & ~limb_mask ) | ( Y->p[i] & limb_mask );
-        Y->p[i] = ( Y->p[i] & ~limb_mask ) | (     tmp & limb_mask );
-    }
+    mbedtls_mpi_core_cond_swap( X->p, Y->p, X->n, swap );
 
 cleanup:
     return( ret );
diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index 95e0d31..22d99a9 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -717,6 +717,84 @@
 mbedtls_mpi_core_lt_ct: x>y (alternating limbs)
 mpi_core_lt_ct:"FF1111111111111111":"11FFFFFFFFFFFFFFFF":0
 
+mbedtls_mpi_core_cond_assign: 1 limb
+mpi_core_cond_assign:"FFFFFFFF":"11111111":4
+
+mbedtls_mpi_core_cond_assign: more limbs #1
+mpi_core_cond_assign:"00000000FFFFFFFF55555555AAAAAAAA":"0123456789ABCDEF0123456789ABCDEF":16
+
+mbedtls_mpi_core_cond_assign: more limbs #2
+mpi_core_cond_assign:"11111111EEEEEEEE77777777CCCCCCCC":"FEDCBA9876543210FEDCBA9876543210":16
+
+mbedtls_mpi_core_cond_assign: more limbs #3
+mpi_core_cond_assign:"562D2B7E83BDC6FF783CEC0D6F46EAE7":"4C314E3B5CEB009C25F3300D5ECF670A":16
+
+mbedtls_mpi_core_cond_assign: copy 256 bytes of limbs
+mpi_core_cond_assign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
+
+mbedtls_mpi_core_cond_assign: copy half of the limbs
+mpi_core_cond_assign:"00000000FFFFFFFF55555555AAAAAAAA":"FEDCBA9876543210FEDCBA9876543210":8
+
+mbedtls_mpi_core_cond_swap: same value
+mpi_core_cond_swap:"FFFFFFFF":"FFFFFFFF":4
+
+mbedtls_mpi_core_cond_swap: 1 limb
+mpi_core_cond_swap:"FFFFFFFF":"11111111":4
+
+mbedtls_mpi_core_cond_swap: more limbs #1
+mpi_core_cond_swap:"00000000FFFFFFFF55555555AAAAAAAA":"0123456789ABCDEF0123456789ABCDEF":16
+
+mbedtls_mpi_core_cond_swap: more limbs #2
+mpi_core_cond_swap:"11111111EEEEEEEE77777777CCCCCCCC":"FEDCBA9876543210FEDCBA9876543210":16
+
+mbedtls_mpi_core_cond_swap: more limbs #3
+mpi_core_cond_swap:"562D2B7E83BDC6FF783CEC0D6F46EAE7":"4C314E3B5CEB009C25F3300D5ECF670A":16
+
+mbedtls_mpi_core_cond_swap: copy 256 bytes of limbs
+mpi_core_cond_swap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
+
+mbedtls_mpi_core_cond_swap: copy half of the limbs
+mpi_core_cond_swap:"00000000FFFFFFFF55555555AAAAAAAA":"FEDCBA9876543210FEDCBA9876543210":8
+
+mbedtls_mpi_mod_raw_cond_assign: 1 limb
+mpi_mod_raw_cond_assign:"FFFFFFFF":"11111111":4
+
+mbedtls_mpi_mod_raw_cond_assign: more limbs #1
+mpi_mod_raw_cond_assign:"00000000FFFFFFFF55555555AAAAAAAA":"0123456789ABCDEF0123456789ABCDEF":16
+
+mbedtls_mpi_mod_raw_cond_assign: more limbs #2
+mpi_mod_raw_cond_assign:"11111111EEEEEEEE77777777CCCCCCCC":"FEDCBA9876543210FEDCBA9876543210":16
+
+mbedtls_mpi_mod_raw_cond_assign: more limbs #3
+mpi_mod_raw_cond_assign:"562D2B7E83BDC6FF783CEC0D6F46EAE7":"4C314E3B5CEB009C25F3300D5ECF670A":16
+
+mbedtls_mpi_mod_raw_cond_assign: copy 256 bytes of limbs
+mpi_mod_raw_cond_assign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
+
+mbedtls_mpi_mod_raw_cond_assign: copy half of the limbs
+mpi_mod_raw_cond_assign:"00000000FFFFFFFF55555555AAAAAAAA":"FEDCBA9876543210FEDCBA9876543210":8
+
+mbedtls_mpi_mod_raw_cond_swap: same value
+mpi_mod_raw_cond_swap:"FFFFFFFF":"FFFFFFFF":4
+
+mbedtls_mpi_mod_raw_cond_swap: 1 limb
+mpi_mod_raw_cond_swap:"FFFFFFFF":"11111111":4
+
+mbedtls_mpi_mod_raw_cond_swap: more limbs #1
+mpi_mod_raw_cond_swap:"00000000FFFFFFFF55555555AAAAAAAA":"0123456789ABCDEF0123456789ABCDEF":16
+
+mbedtls_mpi_mod_raw_cond_swap: more limbs #2
+mpi_mod_raw_cond_swap:"11111111EEEEEEEE77777777CCCCCCCC":"FEDCBA9876543210FEDCBA9876543210":16
+
+mbedtls_mpi_mod_raw_cond_swap: more limbs #3
+mpi_mod_raw_cond_swap:"562D2B7E83BDC6FF783CEC0D6F46EAE7":"4C314E3B5CEB009C25F3300D5ECF670A":16
+
+mbedtls_mpi_mod_raw_cond_swap: copy 256 bytes of limbs
+mpi_mod_raw_cond_swap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
+
+mbedtls_mpi_mod_raw_cond_swap: copy half of the limbs
+mpi_mod_raw_cond_swap:"00000000FFFFFFFF55555555AAAAAAAA":"FEDCBA9876543210FEDCBA9876543210":8
+
 Base test mbedtls_mpi_lt_mpi_ct #1
 mpi_lt_mpi_ct:1:"2B5":1:"2B5":0:0
 
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 9812c56..b699f9c 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -769,6 +769,316 @@
 /* END_CASE */
 
 /* BEGIN_CASE */
+void mpi_core_cond_assign( data_t * input_X,
+                           data_t * input_Y,
+                           int input_bytes )
+{
+    mbedtls_mpi_uint *X = NULL;
+    mbedtls_mpi_uint *Y = NULL;
+    size_t limbs_X = CHARS_TO_LIMBS( input_X->len );
+    size_t limbs_Y = CHARS_TO_LIMBS( input_Y->len );
+    size_t limbs = limbs_X;
+    size_t copy_limbs = CHARS_TO_LIMBS( input_bytes );
+    size_t bytes = limbs * sizeof( mbedtls_mpi_uint );
+    size_t copy_bytes = copy_limbs * sizeof( mbedtls_mpi_uint );
+
+    TEST_EQUAL( limbs_X, limbs_Y );
+    TEST_ASSERT( copy_limbs <= limbs );
+
+    ASSERT_ALLOC( X, limbs );
+    ASSERT_ALLOC( Y, limbs );
+
+    TEST_ASSERT( mbedtls_mpi_core_read_be( X, limbs, input_X->x, input_X->len )
+                 == 0 );
+
+    TEST_ASSERT( mbedtls_mpi_core_read_be( Y, limbs, input_Y->x, input_Y->len )
+                 == 0 );
+
+    /* condition is false */
+    TEST_CF_SECRET( X, bytes );
+    TEST_CF_SECRET( Y, bytes );
+
+    mbedtls_mpi_core_cond_assign( X, Y, copy_limbs, 0 );
+
+    TEST_CF_PUBLIC( X, bytes );
+    TEST_CF_PUBLIC( Y, bytes );
+
+    TEST_ASSERT( memcmp( X, Y, bytes ) != 0 );
+
+    /* condition is true */
+    TEST_CF_SECRET( X, bytes );
+    TEST_CF_SECRET( Y, bytes );
+
+    mbedtls_mpi_core_cond_assign( X, Y, copy_limbs, 1 );
+
+    TEST_CF_PUBLIC( X, bytes );
+    TEST_CF_PUBLIC( Y, bytes );
+
+    /* Check if the given length is copied even it is smaller
+       than the length of the given MPIs. */
+    if( copy_limbs < limbs )
+    {
+        ASSERT_COMPARE( X, copy_bytes, Y, copy_bytes );
+        TEST_ASSERT( memcmp( X, Y, bytes ) != 0 );
+    }
+    else
+        ASSERT_COMPARE( X, bytes, Y, bytes );
+
+exit:
+    mbedtls_free( X );
+    mbedtls_free( Y );
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
+void mpi_core_cond_swap( data_t * input_X,
+                         data_t * input_Y,
+                         int input_bytes )
+{
+    mbedtls_mpi_uint *tmp_X = NULL;
+    mbedtls_mpi_uint *tmp_Y = NULL;
+    mbedtls_mpi_uint *X = NULL;
+    mbedtls_mpi_uint *Y = NULL;
+    size_t limbs_X = CHARS_TO_LIMBS( input_X->len );
+    size_t limbs_Y = CHARS_TO_LIMBS( input_Y->len );
+    size_t limbs = limbs_X;
+    size_t copy_limbs = CHARS_TO_LIMBS( input_bytes );
+    size_t bytes = limbs * sizeof( mbedtls_mpi_uint );
+    size_t copy_bytes = copy_limbs * sizeof( mbedtls_mpi_uint );
+
+    TEST_EQUAL( limbs_X, limbs_Y );
+    TEST_ASSERT( copy_limbs <= limbs );
+
+    ASSERT_ALLOC( tmp_X, limbs );
+    ASSERT_ALLOC( tmp_Y, limbs );
+
+    TEST_ASSERT( mbedtls_mpi_core_read_be( tmp_X, limbs,
+                                           input_X->x, input_X->len )
+                 == 0 );
+    ASSERT_ALLOC( X, limbs );
+    memcpy( X, tmp_X, bytes );
+
+    TEST_ASSERT( mbedtls_mpi_core_read_be( tmp_Y, limbs,
+                                           input_Y->x, input_Y->len )
+                 == 0 );
+    ASSERT_ALLOC( Y, limbs );
+    memcpy( Y, tmp_Y, bytes );
+
+    /* condition is false */
+    TEST_CF_SECRET( X, bytes );
+    TEST_CF_SECRET( Y, bytes );
+
+    mbedtls_mpi_core_cond_swap( X, Y, copy_limbs, 0 );
+
+    TEST_CF_PUBLIC( X, bytes );
+    TEST_CF_PUBLIC( Y, bytes );
+
+    ASSERT_COMPARE( X, bytes, tmp_X, bytes );
+    ASSERT_COMPARE( Y, bytes, tmp_Y, bytes );
+
+    /* condition is true */
+    TEST_CF_SECRET( X, bytes );
+    TEST_CF_SECRET( Y, bytes );
+
+    mbedtls_mpi_core_cond_swap( X, Y, copy_limbs, 1 );
+
+    TEST_CF_PUBLIC( X, bytes );
+    TEST_CF_PUBLIC( Y, bytes );
+
+    /* Check if the given length is copied even it is smaller
+       than the length of the given MPIs. */
+    if( copy_limbs < limbs )
+    {
+        ASSERT_COMPARE( X, copy_bytes, tmp_Y, copy_bytes );
+        ASSERT_COMPARE( Y, copy_bytes, tmp_X, copy_bytes );
+        TEST_ASSERT( memcmp( X, tmp_X, bytes ) != 0 );
+        TEST_ASSERT( memcmp( X, tmp_Y, bytes ) != 0 );
+        TEST_ASSERT( memcmp( Y, tmp_X, bytes ) != 0 );
+        TEST_ASSERT( memcmp( Y, tmp_Y, bytes ) != 0 );
+    }
+    else
+    {
+        ASSERT_COMPARE( X, bytes, tmp_Y, bytes );
+        ASSERT_COMPARE( Y, bytes, tmp_X, bytes );
+    }
+
+exit:
+    mbedtls_free( tmp_X );
+    mbedtls_free( tmp_Y );
+    mbedtls_free( X );
+    mbedtls_free( Y );
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
+void mpi_mod_raw_cond_assign( data_t * input_X,
+                              data_t * input_Y,
+                              int input_bytes )
+{
+    mbedtls_mpi_uint *X = NULL;
+    mbedtls_mpi_uint *Y = NULL;
+    mbedtls_mpi_uint *buff_m = NULL;
+    mbedtls_mpi_mod_modulus m;
+    size_t limbs_X = CHARS_TO_LIMBS( input_X->len );
+    size_t limbs_Y = CHARS_TO_LIMBS( input_Y->len );
+    size_t limbs = limbs_X;
+    size_t copy_limbs = CHARS_TO_LIMBS( input_bytes );
+    size_t bytes = limbs * sizeof( mbedtls_mpi_uint );
+    size_t copy_bytes = copy_limbs * sizeof( mbedtls_mpi_uint );
+
+    TEST_EQUAL( limbs_X, limbs_Y );
+    TEST_ASSERT( copy_limbs <= limbs );
+
+    ASSERT_ALLOC( X, limbs );
+    ASSERT_ALLOC( Y, limbs );
+
+    ASSERT_ALLOC( buff_m, limbs );
+    mbedtls_mpi_mod_modulus_init( &m );
+    TEST_ASSERT( mbedtls_mpi_mod_modulus_setup(
+                        &m, buff_m, copy_limbs,
+                        MBEDTLS_MPI_MOD_EXT_REP_BE,
+                        MBEDTLS_MPI_MOD_REP_MONTGOMERY )
+                 == 0 );
+
+    TEST_ASSERT( mbedtls_mpi_core_read_be( X, limbs,
+                                           input_X->x, input_X->len )
+                 == 0 );
+
+    TEST_ASSERT( mbedtls_mpi_core_read_be( Y, limbs,
+                                           input_Y->x, input_Y->len )
+                 == 0 );
+
+    /* condition is false */
+    TEST_CF_SECRET( X, bytes );
+    TEST_CF_SECRET( Y, bytes );
+
+    mbedtls_mpi_mod_raw_cond_assign( X, Y, &m, 0 );
+
+    TEST_CF_PUBLIC( X, bytes );
+    TEST_CF_PUBLIC( Y, bytes );
+
+    TEST_ASSERT( memcmp( X, Y, bytes ) != 0 );
+
+    /* condition is true */
+    TEST_CF_SECRET( X, bytes );
+    TEST_CF_SECRET( Y, bytes );
+
+    mbedtls_mpi_mod_raw_cond_assign( X, Y, &m, 1 );
+
+    TEST_CF_PUBLIC( X, bytes );
+    TEST_CF_PUBLIC( Y, bytes );
+
+    /* Check if the given length is copied even it is smaller
+       than the length of the given MPIs. */
+    if( copy_limbs <limbs )
+    {
+        ASSERT_COMPARE( X, copy_bytes, Y, copy_bytes );
+        TEST_ASSERT( memcmp( X, Y, bytes ) != 0 );
+    }
+    else
+        ASSERT_COMPARE( X, bytes, Y, bytes );
+
+exit:
+    mbedtls_free( X );
+    mbedtls_free( Y );
+
+    mbedtls_mpi_mod_modulus_free( &m );
+    mbedtls_free( buff_m );
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
+void mpi_mod_raw_cond_swap( data_t * input_X,
+                            data_t * input_Y,
+                            int input_bytes )
+{
+    mbedtls_mpi_uint *tmp_X = NULL;
+    mbedtls_mpi_uint *tmp_Y = NULL;
+    mbedtls_mpi_uint *X = NULL;
+    mbedtls_mpi_uint *Y = NULL;
+    mbedtls_mpi_uint *buff_m = NULL;
+    mbedtls_mpi_mod_modulus m;
+    size_t limbs_X = CHARS_TO_LIMBS( input_X->len );
+    size_t limbs_Y = CHARS_TO_LIMBS( input_Y->len );
+    size_t limbs = limbs_X;
+    size_t copy_limbs = CHARS_TO_LIMBS( input_bytes );
+    size_t bytes = limbs * sizeof( mbedtls_mpi_uint );
+    size_t copy_bytes = copy_limbs * sizeof( mbedtls_mpi_uint );
+
+    TEST_EQUAL( limbs_X, limbs_Y );
+    TEST_ASSERT( copy_limbs <= limbs );
+
+    ASSERT_ALLOC( tmp_X, limbs );
+    ASSERT_ALLOC( tmp_Y, limbs );
+
+    ASSERT_ALLOC( buff_m, copy_limbs );
+    mbedtls_mpi_mod_modulus_init( &m );
+    TEST_ASSERT( mbedtls_mpi_mod_modulus_setup(
+                        &m, buff_m, copy_limbs,
+                        MBEDTLS_MPI_MOD_EXT_REP_BE,
+                        MBEDTLS_MPI_MOD_REP_MONTGOMERY )
+                 == 0 );
+
+    TEST_ASSERT( mbedtls_mpi_core_read_be( tmp_X, limbs, input_X->x, input_X->len )
+                 == 0 );
+    ASSERT_ALLOC( X, limbs );
+    memcpy( X, tmp_X, bytes );
+
+    TEST_ASSERT( mbedtls_mpi_core_read_be( tmp_Y, limbs, input_Y->x, input_Y->len )
+                 == 0 );
+    ASSERT_ALLOC( Y, bytes );
+    memcpy( Y, tmp_Y, bytes );
+
+    /* condition is false */
+    TEST_CF_SECRET( X, bytes );
+    TEST_CF_SECRET( Y, bytes );
+
+    mbedtls_mpi_mod_raw_cond_swap( X, Y, &m, 0 );
+
+    TEST_CF_PUBLIC( X, bytes );
+    TEST_CF_PUBLIC( Y, bytes );
+
+    ASSERT_COMPARE( X, bytes, tmp_X, bytes );
+    ASSERT_COMPARE( Y, bytes, tmp_Y, bytes );
+
+    /* condition is true */
+    TEST_CF_SECRET( X, bytes );
+    TEST_CF_SECRET( Y, bytes );
+
+    mbedtls_mpi_mod_raw_cond_swap( X, Y, &m, 1 );
+
+    TEST_CF_PUBLIC( X, bytes );
+    TEST_CF_PUBLIC( Y, bytes );
+
+    /* Check if the given length is copied even it is smaller
+       than the length of the given MPIs. */
+    if( copy_limbs < limbs )
+    {
+        ASSERT_COMPARE( X, copy_bytes, tmp_Y, copy_bytes );
+        ASSERT_COMPARE( Y, copy_bytes, tmp_X, copy_bytes );
+        TEST_ASSERT( memcmp( X, tmp_X, bytes ) != 0 );
+        TEST_ASSERT( memcmp( X, tmp_Y, bytes ) != 0 );
+        TEST_ASSERT( memcmp( Y, tmp_X, bytes ) != 0 );
+        TEST_ASSERT( memcmp( Y, tmp_Y, bytes ) != 0 );
+    }
+    else
+    {
+        ASSERT_COMPARE( X, bytes, tmp_Y, bytes );
+        ASSERT_COMPARE( Y, bytes, tmp_X, bytes );
+    }
+
+exit:
+    mbedtls_free( tmp_X );
+    mbedtls_free( tmp_Y );
+    mbedtls_free( X );
+    mbedtls_free( Y );
+
+    mbedtls_mpi_mod_modulus_free( &m );
+    mbedtls_free( buff_m );
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
 void mpi_lt_mpi_ct( int size_X, char * input_X,
                     int size_Y, char * input_Y,
                     int input_ret, int input_err )