Full Distribution

src/rsa.cpp

@@ -0,0 +1,92 @@
+/**
+ * Tibia GIMUD Server - a free and open-source MMORPG server emulator
+ * Copyright (C) 2017  Alejandro Mujica <alejandrodemujica@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "otpch.h"
+
+#include "rsa.h"
+
+RSA::RSA()
+{
+	mpz_init(n);
+	mpz_init2(d, 1024);
+}
+
+RSA::~RSA()
+{
+	mpz_clear(n);
+	mpz_clear(d);
+}
+
+void RSA::setKey(const char* pString, const char* qString)
+{
+	mpz_t p, q, e;
+	mpz_init2(p, 1024);
+	mpz_init2(q, 1024);
+	mpz_init(e);
+
+	mpz_set_str(p, pString, 10);
+	mpz_set_str(q, qString, 10);
+
+	// e = 65537
+	mpz_set_ui(e, 65537);
+
+	// n = p * q
+	mpz_mul(n, p, q);
+
+	mpz_t p_1, q_1, pq_1;
+	mpz_init2(p_1, 1024);
+	mpz_init2(q_1, 1024);
+	mpz_init2(pq_1, 1024);
+
+	mpz_sub_ui(p_1, p, 1);
+	mpz_sub_ui(q_1, q, 1);
+
+	// pq_1 = (p -1)(q - 1)
+	mpz_mul(pq_1, p_1, q_1);
+
+	// d = e^-1 mod (p - 1)(q - 1)
+	mpz_invert(d, e, pq_1);
+
+	mpz_clear(p_1);
+	mpz_clear(q_1);
+	mpz_clear(pq_1);
+
+	mpz_clear(p);
+	mpz_clear(q);
+	mpz_clear(e);
+}
+
+void RSA::decrypt(char* msg) const 
+{
+	mpz_t c, m;
+	mpz_init2(c, 1024);
+	mpz_init2(m, 1024);
+
+	mpz_import(c, 128, 1, 1, 0, 0, msg);
+
+	// m = c^d mod n
+	mpz_powm(m, c, d, n);
+
+	size_t count = (mpz_sizeinbase(m, 2) + 7) / 8;
+	memset(msg, 0, 128 - count);
+	mpz_export(msg + (128 - count), nullptr, 1, 1, 0, 0, m);
+
+	mpz_clear(c);
+	mpz_clear(m);
+}