New files for rsa pkcs#1

encryption.

Rev: src/nettle/rsa-decrypt.c:1.1
Rev: src/nettle/rsa-encrypt.c:1.1
Rev: src/nettle/rsa.h:1.10

1 files changed, 77 insertions, 0 deletions

diff --git a/rsa-encrypt.c b/rsa-encrypt.c
new file mode 100644
index 00000000..162bcd9b
--- /dev/null
+++ b/rsa-encrypt.c
@@ -0,0 +1,77 @@
+/* rsa_encrypt.c
+ *
+ * The RSA publickey algorithm. PKCS#1 encryption.
+ */
+
+/* nettle, low-level cryptographics library
+ *
+ * Copyright (C) 2001 Niels Möller
+ *  
+ * The nettle library 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 2.1 of the License, or (at your
+ * option) any later version.
+ * 
+ * The nettle library 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 the nettle library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+#include "rsa.h"
+
+#include "bignum.h"
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+int
+rsa_encrypt(struct rsa_public_key *key,
+	    /* For padding */
+	    void *random_ctx, nettle_random_func random,
+	    unsigned length, const uint8_t *message,
+	    mpz_t gibbberish)
+{
+  uint8_t *em;
+  unsigned padding;
+  unsigned i;
+  
+  /* The message is encoded as a string of the same length as the
+   * modulo n, of the form
+   *
+   *   00 02 pad 00 message
+   *
+   * where padding should be at least 8 pseudorandomly generated
+   * *non-zero* octets. */
+     
+  if (length + 11 < key->size)
+    /* Message too long for this key. */
+    return 0;
+
+  /* At least 8 bits of random padding */
+  padding = key->size - length - 3;
+  assert(padding >= 8);
+  
+  em = alloca(key->size - 1);
+  em[0] = 2;
+
+  random(random_ctx, padding, em + 1);
+
+  /* Replace 0-octets with 1 */
+  for (i = 0; i<padding; i++)
+    if (!em[i+1])
+      em[i+1] = 1;
+  
+  memcpy(em + 1 + padding, message, length);
+
+  nettle_mpz_set_str_256(gibbberish, key->size - 1, em);
+  mpz_powm(gibbberish, gibbberish, key->e, key->n);
+
+  return 1;  
+}