From 5c707978bd9c42447f50ff46eb17ffd64b43e88a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se>
Date: Mon, 14 Jan 2002 13:26:45 +0100
Subject: [PATCH] * rsa.c (rsa_check_size): Changed argument to an mpz_t.
Updated callers. (rsa_prepare_private_key): Compute the size of the key by
computing n = p * q.
* rsa.c (rsa_check_size): New function, for computing and checking
the size of the modulo in octets.
(rsa_prepare_public_key): Usa rsa_check_size.
(rsa_init_private_key): Removed code handling n, e and d.
(rsa_clear_private_key): Likewise.
(rsa_compute_root): Always use CRT.
Rev: src/nettle/rsa.c:1.5
---
rsa.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/rsa.c b/rsa.c
index 6ee9fbe6..bfc31348 100644
--- a/rsa.c
+++ b/rsa.c
@@ -59,10 +59,10 @@ rsa_clear_public_key(struct rsa_public_key *key)
* Returns 0 if the modulo is too small to be useful. */
static unsigned
-rsa_check_size(unsigned bits)
+rsa_check_size(mpz_t n)
{
/* Round upwards */
- unsigned size = (bits + 7) / 8;
+ unsigned size = (mpz_sizeinbase(n, 2) + 7) / 8;
/* 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.
@@ -86,7 +86,7 @@ rsa_prepare_public_key(struct rsa_public_key *key)
return 0;
#endif
- key->size = rsa_check_size(mpz_sizeinbase(key->n, 2));
+ key->size = rsa_check_size(key->n);
return (key->size > 0);
}
@@ -120,10 +120,19 @@ rsa_prepare_private_key(struct rsa_private_key *key)
{
/* FIXME: Add further sanity checks. */
- /* The size of the product is the sum of the sizes of the factors. */
- key->size = rsa_check_size(mpz_sizeinbase(key->p, 2)
- + mpz_sizeinbase(key->p, 2));
+ mpz_t n;
+
+ /* The size of the product is the sum of the sizes of the factors,
+ * or sometimes one less. It's possible but tricky to compute the
+ * size without computing the full product. */
+
+ mpz_init(n);
+ mpz_mul(n, key->p, key->q);
+ key->size = rsa_check_size(n);
+
+ mpz_clear(n);
+
return (key->size > 0);
}
--
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