1 files changed, 69 insertions, 0 deletions
diff --git a/lib/liboqs/src/sig/dilithium/pqcrystals-dilithium_dilithium3_ref/reduce.c b/lib/liboqs/src/sig/dilithium/pqcrystals-dilithium_dilithium3_ref/reduce.c
new file mode 100644
index 000000000..75feff8bc
--- /dev/null
+++ b/lib/liboqs/src/sig/dilithium/pqcrystals-dilithium_dilithium3_ref/reduce.c
@@ -0,0 +1,69 @@
+#include <stdint.h>
+#include "params.h"
+#include "reduce.h"
+
+/*************************************************
+* Name:        montgomery_reduce
+*
+* Description: For finite field element a with -2^{31}Q <= a <= Q*2^31,
+*              compute r \equiv a*2^{-32} (mod Q) such that -Q < r < Q.
+*
+* Arguments:   - int64_t: finite field element a
+*
+* Returns r.
+**************************************************/
+int32_t montgomery_reduce(int64_t a) {
+  int32_t t;
+
+  t = (int64_t)(int32_t)a*QINV;
+  t = (a - (int64_t)t*Q) >> 32;
+  return t;
+}
+
+/*************************************************
+* Name:        reduce32
+*
+* Description: For finite field element a with a <= 2^{31} - 2^{22} - 1,
+*              compute r \equiv a (mod Q) such that -6283009 <= r <= 6283007.
+*
+* Arguments:   - int32_t: finite field element a
+*
+* Returns r.
+**************************************************/
+int32_t reduce32(int32_t a) {
+  int32_t t;
+
+  t = (a + (1 << 22)) >> 23;
+  t = a - t*Q;
+  return t;
+}
+
+/*************************************************
+* Name:        caddq
+*
+* Description: Add Q if input coefficient is negative.
+*
+* Arguments:   - int32_t: finite field element a
+*
+* Returns r.
+**************************************************/
+int32_t caddq(int32_t a) {
+  a += (a >> 31) & Q;
+  return a;
+}
+
+/*************************************************
+* Name:        freeze
+*
+* Description: For finite field element a, compute standard
+*              representative r = a mod^+ Q.
+*
+* Arguments:   - int32_t: finite field element a
+*
+* Returns r.
+**************************************************/
+int32_t freeze(int32_t a) {
+  a = reduce32(a);
+  a = caddq(a);
+  return a;
+}