rc4-based random number generator with seeding

src/generator.cpp

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+
+/*
+ * This file is part of Codecrypt.
+ *
+ * Codecrypt is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * Codecrypt is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Codecrypt. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "generator.h"
+
+#include <fstream>
+#include <vector>
+
+using namespace std;
+
+static inline uint bytes (uint bits)
+{
+	return (bits >> 3) + ( (bits & 7) ? 1 : 0);
+}
+
+void arcfour_rng::seed (uint bits, bool quick)
+{
+	vector<byte> s;
+	ifstream f;
+
+	uint b = bytes (bits);
+	if (b > 256) b = 256;
+
+	f.open (quick ? "/dev/urandom" : "/dev/random", ios::in | ios::binary);
+	s.resize (b);
+	for (uint i = 0; i < b; ++i) f >> s[i];
+	f.close();
+
+	r.load_key (s);
+	r.discard (256);
+}
+

src/generator.h

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+
+/*
+ * This file is part of Codecrypt.
+ *
+ * Codecrypt is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * Codecrypt is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Codecrypt. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _generator_h_
+#define _generator_h_
+
+#include "arcfour.h"
+#include "prng.h"
+
+class arcfour_rng : public prng
+{
+public:
+	arcfour<byte> r;
+
+	arcfour_rng() {
+		r.init (8);
+	}
+
+	~arcfour_rng() {
+		r.clear();
+	}
+
+	void seed (uint bits, bool quick);
+
+	uint random (uint n) {
+		//rand_max is 2^32.
+		return ( (r.gen() << 24) | (r.gen() << 16) | (r.gen() << 8) | r.gen() ) % n;
+	}
+};
+
+#endif