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comparison libtomcrypt/src/pk/ecc/ltc_ecc_map.c @ 382:0cbe8f6dbf9e

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propagate from branch 'au.asn.ucc.matt.ltc.dropbear' (head 2af22fb4e878750b88f80f90d439b316d229796f) to branch 'au.asn.ucc.matt.dropbear' (head 02c413252c90e9de8e03d91e9939dde3029f5c0a)
author Matt Johnston <matt@ucc.asn.au>
date Thu, 11 Jan 2007 02:41:05 +0000
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children f849a5ca2efc
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379:b66a00272a90 382:0cbe8f6dbf9e
1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
2 *
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
5 *
6 * The library is free for all purposes without any express
7 * guarantee it works.
8 *
9 * Tom St Denis, [email protected], http://libtomcrypt.com
10 */
11
12 /* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b
13 *
14 * All curves taken from NIST recommendation paper of July 1999
15 * Available at http://csrc.nist.gov/cryptval/dss.htm
16 */
17 #include "tomcrypt.h"
18
19 /**
20 @file ltc_ecc_map.c
21 ECC Crypto, Tom St Denis
22 */
23
24 #ifdef MECC
25
26 /**
27 Map a projective jacbobian point back to affine space
28 @param P [in/out] The point to map
29 @param modulus The modulus of the field the ECC curve is in
30 @param mp The "b" value from montgomery_setup()
31 @return CRYPT_OK on success
32 */
33 int ltc_ecc_map(ecc_point *P, void *modulus, void *mp)
34 {
35 void *t1, *t2;
36 int err;
37
38 LTC_ARGCHK(P != NULL);
39 LTC_ARGCHK(modulus != NULL);
40 LTC_ARGCHK(mp != NULL);
41
42 if ((err = mp_init_multi(&t1, &t2, NULL)) != CRYPT_OK) {
43 return CRYPT_MEM;
44 }
45
46 /* first map z back to normal */
47 if ((err = mp_montgomery_reduce(P->z, modulus, mp)) != CRYPT_OK) { goto done; }
48
49 /* get 1/z */
50 if ((err = mp_invmod(P->z, modulus, t1)) != CRYPT_OK) { goto done; }
51
52 /* get 1/z^2 and 1/z^3 */
53 if ((err = mp_sqr(t1, t2)) != CRYPT_OK) { goto done; }
54 if ((err = mp_mod(t2, modulus, t2)) != CRYPT_OK) { goto done; }
55 if ((err = mp_mul(t1, t2, t1)) != CRYPT_OK) { goto done; }
56 if ((err = mp_mod(t1, modulus, t1)) != CRYPT_OK) { goto done; }
57
58 /* multiply against x/y */
59 if ((err = mp_mul(P->x, t2, P->x)) != CRYPT_OK) { goto done; }
60 if ((err = mp_montgomery_reduce(P->x, modulus, mp)) != CRYPT_OK) { goto done; }
61 if ((err = mp_mul(P->y, t1, P->y)) != CRYPT_OK) { goto done; }
62 if ((err = mp_montgomery_reduce(P->y, modulus, mp)) != CRYPT_OK) { goto done; }
63 if ((err = mp_set(P->z, 1)) != CRYPT_OK) { goto done; }
64
65 err = CRYPT_OK;
66 done:
67 mp_clear_multi(t1, t2, NULL);
68 return err;
69 }
70
71 #endif
72
73 /* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ltc_ecc_map.c,v $ */
74 /* $Revision: 1.5 $ */
75 /* $Date: 2006/12/04 02:50:11 $ */
76