1 files changed, 14 insertions, 0 deletions

diff --git a/nacl/curvecp/randommod.c b/nacl/curvecp/randommod.c
new file mode 100644
index 00000000..575a627b
--- /dev/null
+++ b/nacl/curvecp/randommod.c
@@ -0,0 +1,14 @@
+#include "randombytes.h"
+
+/* XXX: current implementation is limited to n<2^55 */
+
+long long randommod(long long n)
+{
+  long long result = 0;
+  long long j;
+  unsigned char r[32];
+  if (n <= 1) return 0;
+  randombytes(r,32);
+  for (j = 0;j < 32;++j) result = (result * 256 + (unsigned long long) r[j]) % n;
+  return result;
+}