first implementation of "pseudocode algorithm" (ms_corourke.pdf)

src/ntru_decrypt.c

@@ -19,9 +19,27 @@
  * MA  02110-1301  USA
  */
 
+#include "ntru_decrypt.h"
+
+/*
+ * Legend
+ *
+ * N : highest degree of the polynom
+ * q : "is given" (... mod q)
+ * p : "is given" (... mod p)
+ * f : private key
+ * Fp: inverse of "modulo p"
+ * e : encrypted message
+ * a : result of first multiplication (StarMultiply(f, e, a, N, q))
+ * d : result of second multiplication (StarMultiply(a, Fp , d, N, p)), decrypted message
+ * */
+
 // Require: N , q, p, secret key f , inverse polynomial Fp , and encrypted message e.
 int ntru_decrypt(char *encr_msg, pb_poly *private_key, ntru_context *context, char ** decr_msg){
-	// StarMultiply(f, e, a, N, q)
+	// toDo q = ?, p = ?, fp = ?
+
+	pb_poly *a = first_multiply(private_key, encr_msg, q);// StarMultiply(f, e, a, N, q)
+
 	for(int i = 0, i < N, i++){
 		if(a[i] < 0 ) {
 			a[i] = a[i] + q; // Make all coefficients positive
@@ -30,7 +48,20 @@ int ntru_decrypt(char *encr_msg, pb_poly *private_key, ntru_context *context, ch
 			a[i] = a[i] - q // Shift coefficients of a into range (−q/2, q/2)
 		}
 	}
-	// StarMultiply(a, Fp , d, N, p)
+	char* d = second_multiply(a, fp, p)// StarMultiply(a, Fp , d, N, p)
+
 	// {Decode returns the decrypted message, d, through the argument list.}
-	return 0;
+	return d;
+}
+
+// toDo fix header file definition and types if needed!
+pb_poly* first_multiply(pb_poly *private_key, char *encr_msg, int q) {
+	// toDo a= f*e mod q
+	return NULL;
+}
+
+// toDo fix header file definition and types if needed!
+char* second_multiply(pb_poly *a, pb_poly *fp, int p) {
+	//toDo a*Fp mod p
+	return NULL;
 }

src/ntru_decrypt.h

@@ -26,5 +26,7 @@
 #include "context.h"
 
 int ntru_decrypt(char *encr_msg, pb_poly *private_key, ntru_context *context, char ** decr_msg);
+pb_poly* first_multiply(pb_poly*, char*, int);
+char* first_multiply(pb_poly*, pb_poly*, int);
 
 #endif /* NTRU_DECRYPT */