decryption

actual decryption that doesnt work

include/codecrypt.h

@@ -237,5 +237,17 @@ int generate (pubkey&, privkey&, prng&);
 
 } //namespace ccr
 
+//global overload for iostream operators
+#include <iostream>
+
+std::ostream& operator<< (std::ostream&o, const ccr::polynomial&);
+std::ostream& operator<< (std::ostream&o, const ccr::permutation&);
+std::ostream& operator<< (std::ostream&o, const ccr::gf2m&);
+std::ostream& operator<< (std::ostream&o, const ccr::matrix&);
+std::ostream& operator<< (std::ostream&o, const ccr::bvector&);
+
+
+
+
 #endif // _CODECRYPT_H_
 

lib/mce.cpp

@@ -4,6 +4,8 @@
 using namespace ccr;
 using namespace ccr::mce;
 
+#include "decoding.h"
+
 int ccr::mce::generate (pubkey&pub, privkey&priv, prng&rng, uint m, uint t)
 {
 	//finite field
@@ -69,7 +71,39 @@ int pubkey::encrypt (const bvector& in, bvector&out, prng&rng)
 
 int privkey::decrypt (const bvector&in, bvector&out)
 {
-	return -1; //TODO
+	//remove the P permutation
+	bvector not_permuted;
+	Pinv.permute (in, not_permuted);
+
+	//prepare for decoding
+	permutation hpermInv;
+	hperm.compute_inversion (hpermInv);
+	bvector canonical, syndrome;
+	hperm.permute (not_permuted, canonical);
+	h.mult_vec_right (canonical, syndrome);
+
+	//decode
+	bvector ev;
+	syndrome_decode (syndrome, fld, g, sqInv, ev);
+
+	std::cout << "ERRORS " << ev;
+	//check the error vector. It should have exactly t == deg(g) errors
+	if ( (int) ev.hamming_weight() != g.degree() )
+		return 1;
+
+	//correct the errors
+	canonical.add (ev);
+
+	//shuffle back into systematic order
+	hpermInv.permute (canonical, not_permuted);
+
+	//get rid of redundancy bits
+	not_permuted.resize (Sinv.size() );
+
+	//unscramble the result
+	Sinv.mult_vec_right (not_permuted, out);
+
+	return 0;
 }
 
 int privkey::prepare ()

lib/polynomial.cpp

@@ -57,9 +57,15 @@ void polynomial::mult (const polynomial&b, gf2m&fld)
 {
 	polynomial a = *this;
 	clear();
-	uint i, j, da, db;
+	uint i, j;
+	int da, db;
 	da = a.degree();
 	db = b.degree();
+	if ( (da < 0) || (db < 0) ) { //multiply by zero
+		clear();
+		return;
+	}
+
 	resize (da + db + 1, 0);
 	for (i = 0; i <= da; ++i)
 		if (a[i]) for (j = 0; j <= db; ++j)
@@ -325,9 +331,9 @@ void polynomial::mod_to_fracton (polynomial&a, polynomial&b, polynomial&m, gf2m&
 		a0.swap (a1);
 		a1.swap (t2);
 
-		t1.mult (b1);
-		t1.mod (m);
-		t1.add (b0);
+		t1.mult (b1, fld);
+		t1.mod (m, fld);
+		t1.add (b0, fld);
 		b0.swap (b1);
 		b1.swap (t1);
 	}

src/main.cpp

@@ -7,49 +7,6 @@
 #include <iostream>
 using namespace std;
 
-ostream& operator<< (ostream&o, ccr::polynomial p)
-{
-	o << "polynomial degree " << p.degree() << ':' << endl;
-	for (int i = 0, e = p.degree(); i <= e; ++i) o << p[i] << ' ';
-	o << endl;
-	return o;
-}
-
-ostream& operator<< (ostream&o, ccr::permutation p)
-{
-	o << "permutation over " << p.size() << " elements:" << endl;
-	for (uint i = 0; i < p.size(); ++i) o << p[i] << ' ';
-	o << endl;
-	return o;
-}
-
-ostream& operator<< (ostream&o, ccr::gf2m f)
-{
-	o << "GF(2^" << f.m << ") of " << f.n << " elements, modulus " << f.poly << endl;
-	return o;
-}
-
-ostream& operator<< (ostream&o, ccr::matrix m)
-{
-	uint i, j, h, w;
-	h = m.height();
-	w = m.width();
-	o << "binary " << h << "x" << w << " matrix:" << endl;
-	for (i = 0; i < h; ++i) {
-		for (j = 0; j < w; ++j) o << m[j][i];
-		o << endl;
-	}
-	return o;
-}
-
-ostream& operator<< (ostream&o, ccr::bvector v)
-{
-	o << "vector of " << v.size() << " elements:" << endl;
-	for (uint i = 0, e = v.size(); i < e; ++i) cout << v[i];
-	cout << endl;
-	return o;
-}
-
 class primitiverng : public ccr::prng
 {
 public:
@@ -69,7 +26,7 @@ int main()
 
 	ccr::mce::privkey priv;
 	ccr::mce::pubkey pub;
-	ccr::mce::generate (pub, priv, r, 9, 9);
+	ccr::mce::generate (pub, priv, r, 7, 4);
 
 	cout << "PRIVATE KEY" << endl;
 	cout << priv.fld;