diff --git a/ed25519/ref10/fe.h b/ed25519/ref10/fe.h
index 60c308b..ea34015 100644
--- a/ed25519/ref10/fe.h
+++ b/ed25519/ref10/fe.h
@@ -2,6 +2,7 @@
 #define FE_H
 
 #include "crypto_int32.h"
+#include <stddef.h>
 
 typedef crypto_int32 fe[10];
 
@@ -30,6 +31,7 @@ Bounds on each t[i] vary depending on context.
 #define fe_sq2 crypto_sign_ed25519_ref10_fe_sq2
 #define fe_mul121666 crypto_sign_ed25519_ref10_fe_mul121666
 #define fe_invert crypto_sign_ed25519_ref10_fe_invert
+#define fe_batchinvert crypto_sign_ed25519_ref10_fe_batchinvert
 #define fe_pow22523 crypto_sign_ed25519_ref10_fe_pow22523
 
 extern void fe_frombytes(fe,const unsigned char *);
@@ -51,6 +53,7 @@ extern void fe_sq(fe,const fe);
 extern void fe_sq2(fe,const fe);
 extern void fe_mul121666(fe,const fe);
 extern void fe_invert(fe,const fe);
+extern void fe_batchinvert(fe out[],fe tmp[],const fe in[], size_t num);
 extern void fe_pow22523(fe,const fe);
 
 #endif
diff --git a/ed25519/ref10/fe_batchinvert.c b/ed25519/ref10/fe_batchinvert.c
new file mode 100644
index 0000000..c5a4aaf
--- /dev/null
+++ b/ed25519/ref10/fe_batchinvert.c
@@ -0,0 +1,26 @@
+#include "fe.h"
+
+// tmp MUST != out
+// in MAY == out
+void fe_batchinvert(fe out[],fe tmp[],const fe in[], size_t num)
+{
+  fe acc;
+  fe tmpacc;
+  size_t i;
+
+  fe_1(acc);
+
+  for (i = 0;i < num;++i) {
+    fe_copy(tmp[i],acc);
+    fe_mul(acc,acc,in[i]);
+  }
+
+  fe_invert(acc,acc);
+
+  i = num;
+  while (i--) {
+    fe_mul(tmpacc,acc,in[i]);
+    fe_mul(out[i],acc,tmp[i]);
+    fe_copy(acc,tmpacc);
+  }
+}
diff --git a/main.c b/main.c
index f94cf0a..6eb0281 100644
--- a/main.c
+++ b/main.c
@@ -291,7 +291,7 @@ again:
 		// base32
 		strcpy(base32_to(&sname[direndpos],pk,PUBONION_LEN),".onion");
 		onionready(sname,secret,pubonion.raw);
-		pk[PUBLIC_LEN] = 0;
+		pk[PUBLIC_LEN] = 0; // what is this for?
 		goto initseed;
 	});
 next:
@@ -391,7 +391,7 @@ initseed:
 			// full name
 			strcpy(base32_to(&sname[direndpos],pk,PUBONION_LEN),".onion");
 			onionready(sname,secret,pubonion.raw);
-			pk[PUBLIC_LEN] = 0;
+			pk[PUBLIC_LEN] = 0; // what is this for?
 			// don't reuse same seed
 			goto initseed;
 		});
@@ -494,7 +494,7 @@ initseed:
 			// full name
 			strcpy(base32_to(&sname[direndpos],pk,PUBONION_LEN),".onion");
 			onionready(sname,secret,pubonion.raw);
-			pk[PUBLIC_LEN] = 0;
+			pk[PUBLIC_LEN] = 0; // what is this for?
 		});
 	next:
 		ge_add(&sum, &ge_public,&ge_eightpoint);