1 files changed, 42 insertions, 0 deletions
diff --git a/lib/liboqs/src/kem/kyber/pqcrystals-kyber_kyber512_ref/reduce.c b/lib/liboqs/src/kem/kyber/pqcrystals-kyber_kyber512_ref/reduce.c
new file mode 100644
index 000000000..9d8e7edf8
--- /dev/null
+++ b/lib/liboqs/src/kem/kyber/pqcrystals-kyber_kyber512_ref/reduce.c
@@ -0,0 +1,42 @@
+#include <stdint.h>
+#include "params.h"
+#include "reduce.h"
+
+/*************************************************
+* Name:        montgomery_reduce
+*
+* Description: Montgomery reduction; given a 32-bit integer a, computes
+*              16-bit integer congruent to a * R^-1 mod q, where R=2^16
+*
+* Arguments:   - int32_t a: input integer to be reduced;
+*                           has to be in {-q2^15,...,q2^15-1}
+*
+* Returns:     integer in {-q+1,...,q-1} congruent to a * R^-1 modulo q.
+**************************************************/
+int16_t montgomery_reduce(int32_t a)
+{
+  int16_t t;
+
+  t = (int16_t)a*QINV;
+  t = (a - (int32_t)t*KYBER_Q) >> 16;
+  return t;
+}
+
+/*************************************************
+* Name:        barrett_reduce
+*
+* Description: Barrett reduction; given a 16-bit integer a, computes
+*              centered representative congruent to a mod q in {-(q-1)/2,...,(q-1)/2}
+*
+* Arguments:   - int16_t a: input integer to be reduced
+*
+* Returns:     integer in {-(q-1)/2,...,(q-1)/2} congruent to a modulo q.
+**************************************************/
+int16_t barrett_reduce(int16_t a) {
+  int16_t t;
+  const int16_t v = ((1<<26) + KYBER_Q/2)/KYBER_Q;
+
+  t  = ((int32_t)v*a + (1<<25)) >> 26;
+  t *= KYBER_Q;
+  return a - t;
+}