From 3a3d2d8659d33746cb6fbed8a390fdc5d2c66541 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se>
Date: Mon, 11 Feb 2002 18:54:35 +0100
Subject: [PATCH] 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
---
rsa-decrypt.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++
rsa-encrypt.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++
rsa.h | 37 +++++++++++++++++++++----
3 files changed, 184 insertions(+), 5 deletions(-)
create mode 100644 rsa-decrypt.c
create mode 100644 rsa-encrypt.c
diff --git a/rsa-decrypt.c b/rsa-decrypt.c
new file mode 100644
index 00000000..a4cef7ad
--- /dev/null
+++ b/rsa-decrypt.c
@@ -0,0 +1,75 @@
+/* rsa_decrypt.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_decrypt(struct rsa_private_key *key,
+ unsigned *length, uint8_t *message,
+ const mpz_t gibberish)
+{
+ uint8_t *em;
+ uint8_t *terminator;
+ unsigned padding;
+ unsigned message_length;
+
+ mpz_t m;
+
+ mpz_init(m);
+ rsa_compute_root(key, m, gibberish);
+
+ em = alloca(key->size);
+ nettle_mpz_get_str_256(key->size, em, m);
+ mpz_clear(m);
+
+ /* Check format */
+ if (em[0] || em[1] != 2)
+ return 0;
+
+ terminator = memchr(em + 2, 0, key->size - 2);
+
+ if (!terminator)
+ return 0;
+
+ padding = terminator - (em + 2);
+ if (padding < 8)
+ return 0;
+
+ message_length = key->size - 3 - padding;
+
+ if (*length < message_length)
+ return 0;
+
+ memcpy(message, terminator + 1, message_length);
+ *length = message_length;
+
+ return 1;
+}
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;
+}
diff --git a/rsa.h b/rsa.h
index e480937e..6da8b7bb 100644
--- a/rsa.h
+++ b/rsa.h
@@ -32,6 +32,13 @@
#include "md5.h"
#include "sha.h"
+/* Randomness function. This typedef doesn't really belong here, but
+ * so far it's used only by rsa functions (encryption and key
+ * generation) */
+typedef void (*nettle_random_func)(void *ctx,
+ unsigned length, uint8_t *dst);
+
+
/* For PKCS#1 to make sense, the size of the modulo, in octets, must
* be at least 11 + the length of the DER-encoded Digest Info.
*
@@ -144,6 +151,31 @@ rsa_sha1_verify(struct rsa_public_key *key,
struct sha1_ctx *hash,
const mpz_t signature);
+
+/* RSA encryption, using PKCS#1 */
+/* FIXME: These functions uses the v1.5 padding. What should the v2
+ * (OAEP) functions be called? */
+
+/* Returns 1 on success, 0 on failure, which happens if the
+ * message is too long for the key. */
+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);
+
+/* Message must point to a buffer of size *LENGTH. KEY->size is enough
+ * for all valid messages. On success, *LENGTH is updated to reflect
+ * the actual length of the message. Returns 1 on success, 0 on
+ * failure, which happens if decryption failed or if the message
+ * didn't fit. */
+int
+rsa_decrypt(struct rsa_private_key *key,
+ unsigned *length, uint8_t *message,
+ const mpz_t gibberish);
+
+
/* Compute x, the e:th root of m. Calling it with x == m is allowed. */
void
rsa_compute_root(struct rsa_private_key *key, mpz_t x, const mpz_t m);
@@ -151,11 +183,6 @@ rsa_compute_root(struct rsa_private_key *key, mpz_t x, const mpz_t m);
/* Key generation */
-/* Randomness function. This typedef doesn't really belong here, but
- * so far it's used only by the rsa key generator. */
-typedef void (*nettle_random_func)(void *ctx,
- unsigned length, uint8_t *dst);
-
/* Progress report function. */
typedef void (*nettle_progress_func)(void *ctx,
int c);
--
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