1 files changed, 57 insertions, 0 deletions
diff --git a/src/crypto/shen_ed25519_ref/ref10/fe_sub.c b/src/crypto/shen_ed25519_ref/ref10/fe_sub.c
new file mode 100644
index 000000000..6e26b7df8
--- /dev/null
+++ b/src/crypto/shen_ed25519_ref/ref10/fe_sub.c
@@ -0,0 +1,57 @@
+#include "fe.h"
+
+/*
+h = f - g
+Can overlap h with f or g.
+
+Preconditions:
+   |f| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
+   |g| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
+
+Postconditions:
+   |h| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.
+*/
+
+void fe_sub(fe h,const fe f,const fe g)
+{
+  crypto_int32 f0 = f[0];
+  crypto_int32 f1 = f[1];
+  crypto_int32 f2 = f[2];
+  crypto_int32 f3 = f[3];
+  crypto_int32 f4 = f[4];
+  crypto_int32 f5 = f[5];
+  crypto_int32 f6 = f[6];
+  crypto_int32 f7 = f[7];
+  crypto_int32 f8 = f[8];
+  crypto_int32 f9 = f[9];
+  crypto_int32 g0 = g[0];
+  crypto_int32 g1 = g[1];
+  crypto_int32 g2 = g[2];
+  crypto_int32 g3 = g[3];
+  crypto_int32 g4 = g[4];
+  crypto_int32 g5 = g[5];
+  crypto_int32 g6 = g[6];
+  crypto_int32 g7 = g[7];
+  crypto_int32 g8 = g[8];
+  crypto_int32 g9 = g[9];
+  crypto_int32 h0 = f0 - g0;
+  crypto_int32 h1 = f1 - g1;
+  crypto_int32 h2 = f2 - g2;
+  crypto_int32 h3 = f3 - g3;
+  crypto_int32 h4 = f4 - g4;
+  crypto_int32 h5 = f5 - g5;
+  crypto_int32 h6 = f6 - g6;
+  crypto_int32 h7 = f7 - g7;
+  crypto_int32 h8 = f8 - g8;
+  crypto_int32 h9 = f9 - g9;
+  h[0] = h0;
+  h[1] = h1;
+  h[2] = h2;
+  h[3] = h3;
+  h[4] = h4;
+  h[5] = h5;
+  h[6] = h6;
+  h[7] = h7;
+  h[8] = h8;
+  h[9] = h9;
+}