add zeromem engine

anti memory leakage attack

engines/zeromem/ec_inv.c

@@ -0,0 +1,104 @@
+#include "ec.h"
+#include "string.h"
+#include "stdio.h"
+
+int is_one(mm_256* a) 
+{
+	int i;
+	if (a->iv[0] != 1)
+		return 0;
+	
+	for (i = 1; i < 4; i++) {
+		if (a->iv[i] != 0)
+			return 0;
+	}
+
+	return 1;
+	
+}
+
+void shift_right(mm_256* a)
+{
+	int i;
+	
+	for (i = 0; i < 3; i++) {
+		a->iv[i] = (a->iv[i] >> 1) | (a->iv[i + 1] << 63);
+	}
+	a->iv[3] >>= 1;
+}
+
+void add(mm_256* a, mm_256*b) 
+{
+	int i;
+	
+	for (i = 0; i < 4; i++) {
+		b->iv[i] = b->iv[i] ^ a->iv[i];
+	}
+}
+
+int deg(mm_256* a) 
+{
+	int cnt = 0;
+	int i;
+	uint64_t c;
+	
+	for (i = 3; i >= 0; i--) {
+		if (a->iv[i] != 0) {
+			break;
+		}
+	}
+	cnt = i * 64;
+	c = a->iv[i];
+	while (c != 0) {
+		cnt ++;
+		c >>= 1;
+	}
+	return cnt;
+}
+
+void gf2m_inv(mm_256* a, mm_256 *r)
+{
+	mm_256 b, c, u, v, f, t;
+	
+	// b = 1
+	memset(&b, 0, sizeof(b));
+	b.iv[0] = 1;
+	// c = 0
+	memset(&c, 0, sizeof(c));
+	// u = a
+	u = *a;
+	// v = f
+	memset(&v, 0, sizeof(v));
+	memset(&f, 0, sizeof(f));
+	f.bv[0] = 0xc9;
+	f.bv[20] = 0x8;
+	v = f;
+
+	while (1) {
+		while ((u.bv[0] & 0x1) == 0) {
+			shift_right(&u);
+			
+			if ((b.iv[0] & 0x1) != 0) {
+				add(&f, &b);
+			}
+			shift_right(&b);
+		}
+		if (is_one(&u))
+			break;
+		
+		if (deg(&u) < deg(&v)) {
+			t = u;
+			u = v;
+			v = t;
+			
+			t = b;
+			b = c;
+			c = t;
+		}
+		add(&v, &u);
+		add(&c, &b);
+		/* break; */
+	}
+	
+	*r = b;
+}