Add bignum_new.c starting with MPI_CORE(montmul) for Montgomery multiplication
Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
diff --git a/library/bignum_new.c b/library/bignum_new.c
new file mode 100644
index 0000000..29c1212
--- /dev/null
+++ b/library/bignum_new.c
@@ -0,0 +1,126 @@
+/*
+ * Multi-precision integer library
+ *
+ * Copyright The Mbed TLS Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "common.h"
+
+#if defined(MBEDTLS_BIGNUM_C)
+
+#include "mbedtls/bignum.h"
+#include "bignum_core.h"
+#include "bn_mul.h"
+
+#include <string.h>
+
+void MPI_CORE(montmul)( mbedtls_mpi_uint *X,
+ const mbedtls_mpi_uint *A,
+ const mbedtls_mpi_uint *B,
+ size_t B_len,
+ const mbedtls_mpi_uint *N,
+ size_t n,
+ mbedtls_mpi_uint mm,
+ mbedtls_mpi_uint *T )
+{
+ memset( T, 0, (2*n+1)*ciL );
+
+ for( size_t i = 0; i < n; i++, T++ )
+ {
+ mbedtls_mpi_uint u0, u1;
+ /* T = (T + u0*B + u1*N) / 2^biL */
+ u0 = A[i];
+ u1 = ( T[0] + u0 * B[0] ) * mm;
+
+ (void) MPI_CORE(mla)( T, n + 2, B, B_len, u0 );
+ (void) MPI_CORE(mla)( T, n + 2, N, n, u1 );
+ }
+
+ mbedtls_mpi_uint carry, borrow, fixup;
+
+ carry = T[n];
+ borrow = MPI_CORE(sub)( X, T, N, n );
+ fixup = carry < borrow;
+ (void) MPI_CORE(add_if)( X, N, n, fixup );
+}
+
+mbedtls_mpi_uint MPI_CORE(mla)( mbedtls_mpi_uint *d, size_t d_len,
+ const mbedtls_mpi_uint *s, size_t s_len,
+ mbedtls_mpi_uint b )
+{
+ mbedtls_mpi_uint c = 0; /* carry */
+ if( d_len < s_len )
+ s_len = d_len;
+ size_t excess_len = d_len - s_len;
+ size_t steps_x8 = s_len / 8;
+ size_t steps_x1 = s_len & 7;
+
+ while( steps_x8-- )
+ {
+ MULADDC_X8_INIT
+ MULADDC_X8_CORE
+ MULADDC_X8_STOP
+ }
+
+ while( steps_x1-- )
+ {
+ MULADDC_X1_INIT
+ MULADDC_X1_CORE
+ MULADDC_X1_STOP
+ }
+
+ while( excess_len-- )
+ {
+ *d += c; c = ( *d < c ); d++;
+ }
+
+ return( c );
+}
+
+mbedtls_mpi_uint MPI_CORE(sub)( mbedtls_mpi_uint *d,
+ const mbedtls_mpi_uint *l,
+ const mbedtls_mpi_uint *r,
+ size_t n )
+{
+ mbedtls_mpi_uint c = 0, t, z;
+
+ for( size_t i = 0; i < n; i++ )
+ {
+ z = ( l[i] < c ); t = l[i] - c;
+ c = ( t < r[i] ) + z; d[i] = t - r[i];
+ }
+
+ return( c );
+}
+
+mbedtls_mpi_uint MPI_CORE(add_if)( mbedtls_mpi_uint *d,
+ const mbedtls_mpi_uint *r,
+ size_t n,
+ unsigned cond )
+{
+ mbedtls_mpi_uint c = 0, t;
+ for( size_t i = 0; i < n; i++ )
+ {
+ mbedtls_mpi_uint add = cond * r[i];
+ t = c;
+ t += d[i]; c = ( t < d[i] );
+ t += add; c += ( t < add );
+ d[i] = t;
+ }
+ return( c );
+}
+
+#endif /* MBEDTLS_BIGNUM_C */