/* * Elliptic curves over GF(p) * * Copyright (C) 2006-2013, Brainspark B.V. * * This file is part of PolarSSL (http://www.polarssl.org) * Lead Maintainer: Paul Bakker * * All rights reserved. * * 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. */ /* * References: * * SEC1 http://www.secg.org/index.php?action=secg,docs_secg * GECC = Guide to Elliptic Curve Cryptography - Hankerson, Menezes, Vanstone * FIPS 186-3 http://csrc.nist.gov/publications/fips/fips186-3/fips_186-3.pdf * RFC 4492 for the related TLS structures and constants * * [1] OKEYA, Katsuyuki and TAKAGI, Tsuyoshi. The width-w NAF method provides * small memory and fast elliptic scalar multiplications secure against * side channel attacks. In : Topics in Cryptology—CT-RSA 2003. Springer * Berlin Heidelberg, 2003. p. 328-343. * . * * [2] CORON, Jean-Sébastien. Resistance against differential power analysis * for elliptic curve cryptosystems. In : Cryptographic Hardware and * Embedded Systems. Springer Berlin Heidelberg, 1999. p. 292-302. * */ #include "polarssl/config.h" #if defined(POLARSSL_ECP_C) #include "polarssl/ecp.h" #if defined(POLARSSL_MEMORY_C) #include "polarssl/memory.h" #else #define polarssl_malloc malloc #define polarssl_free free #endif #include #include #if defined(POLARSSL_SELF_TEST) /* * Counts of point addition and doubling operations. * Used to test resistance of point multiplication to simple timing attacks. */ unsigned long add_count, dbl_count; #endif /* * List of supported curves: * - internal ID * - TLS NamedCurve ID (RFC 4492 sec. 5.1.1, RFC 7071 sec. 2) * - size in bits * - readable name */ const ecp_curve_info ecp_supported_curves[] = { #if defined(POLARSSL_ECP_DP_BP512R1_ENABLED) { POLARSSL_ECP_DP_BP512R1, 28, 512, "brainpool512r1" }, #endif #if defined(POLARSSL_ECP_DP_BP384R1_ENABLED) { POLARSSL_ECP_DP_BP384R1, 27, 384, "brainpool384r1" }, #endif #if defined(POLARSSL_ECP_DP_BP256R1_ENABLED) { POLARSSL_ECP_DP_BP256R1, 26, 256, "brainpool256r1" }, #endif #if defined(POLARSSL_ECP_DP_SECP521R1_ENABLED) { POLARSSL_ECP_DP_SECP521R1, 25, 521, "secp521r1" }, #endif #if defined(POLARSSL_ECP_DP_SECP384R1_ENABLED) { POLARSSL_ECP_DP_SECP384R1, 24, 384, "secp384r1" }, #endif #if defined(POLARSSL_ECP_DP_SECP256R1_ENABLED) { POLARSSL_ECP_DP_SECP256R1, 23, 256, "secp256r1" }, #endif #if defined(POLARSSL_ECP_DP_SECP224R1_ENABLED) { POLARSSL_ECP_DP_SECP224R1, 21, 224, "secp224r1" }, #endif #if defined(POLARSSL_ECP_DP_SECP192R1_ENABLED) { POLARSSL_ECP_DP_SECP192R1, 19, 192, "secp192r1" }, #endif { POLARSSL_ECP_DP_NONE, 0, 0, NULL }, }; /* * List of supported curves and associated info */ const ecp_curve_info *ecp_curve_list( void ) { return ecp_supported_curves; } /* * Get the curve info for the internal identifer */ const ecp_curve_info *ecp_curve_info_from_grp_id( ecp_group_id grp_id ) { const ecp_curve_info *curve_info; for( curve_info = ecp_curve_list(); curve_info->grp_id != POLARSSL_ECP_DP_NONE; curve_info++ ) { if( curve_info->grp_id == grp_id ) return( curve_info ); } return( NULL ); } /* * Get the curve info from the TLS identifier */ const ecp_curve_info *ecp_curve_info_from_tls_id( uint16_t tls_id ) { const ecp_curve_info *curve_info; for( curve_info = ecp_curve_list(); curve_info->grp_id != POLARSSL_ECP_DP_NONE; curve_info++ ) { if( curve_info->tls_id == tls_id ) return( curve_info ); } return( NULL ); } /* * Initialize (the components of) a point */ void ecp_point_init( ecp_point *pt ) { if( pt == NULL ) return; mpi_init( &pt->X ); mpi_init( &pt->Y ); mpi_init( &pt->Z ); } /* * Initialize (the components of) a group */ void ecp_group_init( ecp_group *grp ) { if( grp == NULL ) return; memset( grp, 0, sizeof( ecp_group ) ); } /* * Initialize (the components of) a key pair */ void ecp_keypair_init( ecp_keypair *key ) { if ( key == NULL ) return; ecp_group_init( &key->grp ); mpi_init( &key->d ); ecp_point_init( &key->Q ); } /* * Unallocate (the components of) a point */ void ecp_point_free( ecp_point *pt ) { if( pt == NULL ) return; mpi_free( &( pt->X ) ); mpi_free( &( pt->Y ) ); mpi_free( &( pt->Z ) ); } /* * Unallocate (the components of) a group */ void ecp_group_free( ecp_group *grp ) { size_t i; if( grp == NULL ) return; mpi_free( &grp->P ); mpi_free( &grp->A ); mpi_free( &grp->B ); ecp_point_free( &grp->G ); mpi_free( &grp->N ); if( grp->T != NULL ) { for( i = 0; i < grp->T_size; i++ ) ecp_point_free( &grp->T[i] ); polarssl_free( grp->T ); } memset( grp, 0, sizeof( ecp_group ) ); } /* * Unallocate (the components of) a key pair */ void ecp_keypair_free( ecp_keypair *key ) { if ( key == NULL ) return; ecp_group_free( &key->grp ); mpi_free( &key->d ); ecp_point_free( &key->Q ); } /* * Copy the contents of a point */ int ecp_copy( ecp_point *P, const ecp_point *Q ) { int ret; MPI_CHK( mpi_copy( &P->X, &Q->X ) ); MPI_CHK( mpi_copy( &P->Y, &Q->Y ) ); MPI_CHK( mpi_copy( &P->Z, &Q->Z ) ); cleanup: return( ret ); } /* * Copy the contents of a group object */ int ecp_group_copy( ecp_group *dst, const ecp_group *src ) { return ecp_use_known_dp( dst, src->id ); } /* * Set point to zero */ int ecp_set_zero( ecp_point *pt ) { int ret; MPI_CHK( mpi_lset( &pt->X , 1 ) ); MPI_CHK( mpi_lset( &pt->Y , 1 ) ); MPI_CHK( mpi_lset( &pt->Z , 0 ) ); cleanup: return( ret ); } /* * Tell if a point is zero */ int ecp_is_zero( ecp_point *pt ) { return( mpi_cmp_int( &pt->Z, 0 ) == 0 ); } /* * Import a non-zero point from ASCII strings */ int ecp_point_read_string( ecp_point *P, int radix, const char *x, const char *y ) { int ret; MPI_CHK( mpi_read_string( &P->X, radix, x ) ); MPI_CHK( mpi_read_string( &P->Y, radix, y ) ); MPI_CHK( mpi_lset( &P->Z, 1 ) ); cleanup: return( ret ); } /* * Export a point into unsigned binary data (SEC1 2.3.3) */ int ecp_point_write_binary( const ecp_group *grp, const ecp_point *P, int format, size_t *olen, unsigned char *buf, size_t buflen ) { int ret = 0; size_t plen; if( format != POLARSSL_ECP_PF_UNCOMPRESSED && format != POLARSSL_ECP_PF_COMPRESSED ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); /* * Common case: P == 0 */ if( mpi_cmp_int( &P->Z, 0 ) == 0 ) { if( buflen < 1 ) return( POLARSSL_ERR_ECP_BUFFER_TOO_SMALL ); buf[0] = 0x00; *olen = 1; return( 0 ); } plen = mpi_size( &grp->P ); if( format == POLARSSL_ECP_PF_UNCOMPRESSED ) { *olen = 2 * plen + 1; if( buflen < *olen ) return( POLARSSL_ERR_ECP_BUFFER_TOO_SMALL ); buf[0] = 0x04; MPI_CHK( mpi_write_binary( &P->X, buf + 1, plen ) ); MPI_CHK( mpi_write_binary( &P->Y, buf + 1 + plen, plen ) ); } else if( format == POLARSSL_ECP_PF_COMPRESSED ) { *olen = plen + 1; if( buflen < *olen ) return( POLARSSL_ERR_ECP_BUFFER_TOO_SMALL ); buf[0] = 0x02 + mpi_get_bit( &P->Y, 0 ); MPI_CHK( mpi_write_binary( &P->X, buf + 1, plen ) ); } cleanup: return( ret ); } /* * Import a point from unsigned binary data (SEC1 2.3.4) */ int ecp_point_read_binary( const ecp_group *grp, ecp_point *pt, const unsigned char *buf, size_t ilen ) { int ret; size_t plen; if( ilen == 1 && buf[0] == 0x00 ) return( ecp_set_zero( pt ) ); plen = mpi_size( &grp->P ); if( ilen != 2 * plen + 1 || buf[0] != 0x04 ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); MPI_CHK( mpi_read_binary( &pt->X, buf + 1, plen ) ); MPI_CHK( mpi_read_binary( &pt->Y, buf + 1 + plen, plen ) ); MPI_CHK( mpi_lset( &pt->Z, 1 ) ); cleanup: return( ret ); } /* * Import a point from a TLS ECPoint record (RFC 4492) * struct { * opaque point <1..2^8-1>; * } ECPoint; */ int ecp_tls_read_point( const ecp_group *grp, ecp_point *pt, const unsigned char **buf, size_t buf_len ) { unsigned char data_len; const unsigned char *buf_start; /* * We must have at least two bytes (1 for length, at least of for data) */ if( buf_len < 2 ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); data_len = *(*buf)++; if( data_len < 1 || data_len > buf_len - 1 ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); /* * Save buffer start for read_binary and update buf */ buf_start = *buf; *buf += data_len; return ecp_point_read_binary( grp, pt, buf_start, data_len ); } /* * Export a point as a TLS ECPoint record (RFC 4492) * struct { * opaque point <1..2^8-1>; * } ECPoint; */ int ecp_tls_write_point( const ecp_group *grp, const ecp_point *pt, int format, size_t *olen, unsigned char *buf, size_t blen ) { int ret; /* * buffer length must be at least one, for our length byte */ if( blen < 1 ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); if( ( ret = ecp_point_write_binary( grp, pt, format, olen, buf + 1, blen - 1) ) != 0 ) return( ret ); /* * write length to the first byte and update total length */ buf[0] = (unsigned char) *olen; ++*olen; return 0; } /* * Import an ECP group from ASCII strings, general case (A used) */ static int ecp_group_read_string_gen( ecp_group *grp, int radix, const char *p, const char *a, const char *b, const char *gx, const char *gy, const char *n) { int ret; MPI_CHK( mpi_read_string( &grp->P, radix, p ) ); MPI_CHK( mpi_read_string( &grp->A, radix, a ) ); MPI_CHK( mpi_read_string( &grp->B, radix, b ) ); MPI_CHK( ecp_point_read_string( &grp->G, radix, gx, gy ) ); MPI_CHK( mpi_read_string( &grp->N, radix, n ) ); grp->pbits = mpi_msb( &grp->P ); grp->nbits = mpi_msb( &grp->N ); cleanup: if( ret != 0 ) ecp_group_free( grp ); return( ret ); } /* * Import an ECP group from ASCII strings, case A == -3 */ int ecp_group_read_string( ecp_group *grp, int radix, const char *p, const char *b, const char *gx, const char *gy, const char *n) { int ret; MPI_CHK( ecp_group_read_string_gen( grp, radix, p, "00", b, gx, gy, n ) ); MPI_CHK( mpi_add_int( &grp->A, &grp->P, -3 ) ); cleanup: if( ret != 0 ) ecp_group_free( grp ); return( ret ); } /* * Domain parameters for secp192r1 */ #define SECP192R1_P \ "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFFFFFFFFFFFF" #define SECP192R1_B \ "64210519E59C80E70FA7E9AB72243049FEB8DEECC146B9B1" #define SECP192R1_GX \ "188DA80EB03090F67CBF20EB43A18800F4FF0AFD82FF1012" #define SECP192R1_GY \ "07192B95FFC8DA78631011ED6B24CDD573F977A11E794811" #define SECP192R1_N \ "FFFFFFFFFFFFFFFFFFFFFFFF99DEF836146BC9B1B4D22831" /* * Domain parameters for secp224r1 */ #define SECP224R1_P \ "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF000000000000000000000001" #define SECP224R1_B \ "B4050A850C04B3ABF54132565044B0B7D7BFD8BA270B39432355FFB4" #define SECP224R1_GX \ "B70E0CBD6BB4BF7F321390B94A03C1D356C21122343280D6115C1D21" #define SECP224R1_GY \ "BD376388B5F723FB4C22DFE6CD4375A05A07476444D5819985007E34" #define SECP224R1_N \ "FFFFFFFFFFFFFFFFFFFFFFFFFFFF16A2E0B8F03E13DD29455C5C2A3D" /* * Domain parameters for secp256r1 */ #define SECP256R1_P \ "FFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFF" #define SECP256R1_B \ "5AC635D8AA3A93E7B3EBBD55769886BC651D06B0CC53B0F63BCE3C3E27D2604B" #define SECP256R1_GX \ "6B17D1F2E12C4247F8BCE6E563A440F277037D812DEB33A0F4A13945D898C296" #define SECP256R1_GY \ "4FE342E2FE1A7F9B8EE7EB4A7C0F9E162BCE33576B315ECECBB6406837BF51F5" #define SECP256R1_N \ "FFFFFFFF00000000FFFFFFFFFFFFFFFFBCE6FAADA7179E84F3B9CAC2FC632551" /* * Domain parameters for secp384r1 */ #define SECP384R1_P \ "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF" \ "FFFFFFFFFFFFFFFEFFFFFFFF0000000000000000FFFFFFFF" #define SECP384R1_B \ "B3312FA7E23EE7E4988E056BE3F82D19181D9C6EFE814112" \ "0314088F5013875AC656398D8A2ED19D2A85C8EDD3EC2AEF" #define SECP384R1_GX \ "AA87CA22BE8B05378EB1C71EF320AD746E1D3B628BA79B98" \ "59F741E082542A385502F25DBF55296C3A545E3872760AB7" #define SECP384R1_GY \ "3617DE4A96262C6F5D9E98BF9292DC29F8F41DBD289A147C" \ "E9DA3113B5F0B8C00A60B1CE1D7E819D7A431D7C90EA0E5F" #define SECP384R1_N \ "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF" \ "C7634D81F4372DDF581A0DB248B0A77AECEC196ACCC52973" /* * Domain parameters for secp521r1 */ #define SECP521R1_P \ "000001FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF" \ "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF" \ "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF" #define SECP521R1_B \ "00000051953EB9618E1C9A1F929A21A0B68540EEA2DA725B" \ "99B315F3B8B489918EF109E156193951EC7E937B1652C0BD" \ "3BB1BF073573DF883D2C34F1EF451FD46B503F00" #define SECP521R1_GX \ "000000C6858E06B70404E9CD9E3ECB662395B4429C648139" \ "053FB521F828AF606B4D3DBAA14B5E77EFE75928FE1DC127" \ "A2FFA8DE3348B3C1856A429BF97E7E31C2E5BD66" #define SECP521R1_GY \ "0000011839296A789A3BC0045C8A5FB42C7D1BD998F54449" \ "579B446817AFBD17273E662C97EE72995EF42640C550B901" \ "3FAD0761353C7086A272C24088BE94769FD16650" #define SECP521R1_N \ "000001FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF" \ "FFFFFFFFFFFFFFFFFFFFFFFA51868783BF2F966B7FCC0148" \ "F709A5D03BB5C9B8899C47AEBB6FB71E91386409" /* * Domain parameters for brainpoolP256r1 (RFC 5639 3.4) */ #define BP256R1_P \ "A9FB57DBA1EEA9BC3E660A909D838D726E3BF623D52620282013481D1F6E5377" #define BP256R1_A \ "7D5A0975FC2C3057EEF67530417AFFE7FB8055C126DC5C6CE94A4B44F330B5D9" #define BP256R1_B \ "26DC5C6CE94A4B44F330B5D9BBD77CBF958416295CF7E1CE6BCCDC18FF8C07B6" #define BP256R1_GX \ "8BD2AEB9CB7E57CB2C4B482FFC81B7AFB9DE27E1E3BD23C23A4453BD9ACE3262" #define BP256R1_GY \ "547EF835C3DAC4FD97F8461A14611DC9C27745132DED8E545C1D54C72F046997" #define BP256R1_N \ "A9FB57DBA1EEA9BC3E660A909D838D718C397AA3B561A6F7901E0E82974856A7" /* * Domain parameters for brainpoolP384r1 (RFC 5639 3.6) */ #define BP384R1_P \ "8CB91E82A3386D280F5D6F7E50E641DF152F7109ED5456B412B1DA197FB711" \ "23ACD3A729901D1A71874700133107EC53" #define BP384R1_A \ "7BC382C63D8C150C3C72080ACE05AFA0C2BEA28E4FB22787139165EFBA91F9" \ "0F8AA5814A503AD4EB04A8C7DD22CE2826" #define BP384R1_B \ "04A8C7DD22CE28268B39B55416F0447C2FB77DE107DCD2A62E880EA53EEB62" \ "D57CB4390295DBC9943AB78696FA504C11" #define BP384R1_GX \ "1D1C64F068CF45FFA2A63A81B7C13F6B8847A3E77EF14FE3DB7FCAFE0CBD10" \ "E8E826E03436D646AAEF87B2E247D4AF1E" #define BP384R1_GY \ "8ABE1D7520F9C2A45CB1EB8E95CFD55262B70B29FEEC5864E19C054FF99129" \ "280E4646217791811142820341263C5315" #define BP384R1_N \ "8CB91E82A3386D280F5D6F7E50E641DF152F7109ED5456B31F166E6CAC0425" \ "A7CF3AB6AF6B7FC3103B883202E9046565" /* * Domain parameters for brainpoolP512r1 (RFC 5639 3.7) */ #define BP512R1_P \ "AADD9DB8DBE9C48B3FD4E6AE33C9FC07CB308DB3B3C9D20ED6639CCA703308" \ "717D4D9B009BC66842AECDA12AE6A380E62881FF2F2D82C68528AA6056583A48F3" #define BP512R1_A \ "7830A3318B603B89E2327145AC234CC594CBDD8D3DF91610A83441CAEA9863" \ "BC2DED5D5AA8253AA10A2EF1C98B9AC8B57F1117A72BF2C7B9E7C1AC4D77FC94CA" #define BP512R1_B \ "3DF91610A83441CAEA9863BC2DED5D5AA8253AA10A2EF1C98B9AC8B57F1117" \ "A72BF2C7B9E7C1AC4D77FC94CADC083E67984050B75EBAE5DD2809BD638016F723" #define BP512R1_GX \ "81AEE4BDD82ED9645A21322E9C4C6A9385ED9F70B5D916C1B43B62EEF4D009" \ "8EFF3B1F78E2D0D48D50D1687B93B97D5F7C6D5047406A5E688B352209BCB9F822" #define BP512R1_GY \ "7DDE385D566332ECC0EABFA9CF7822FDF209F70024A57B1AA000C55B881F81" \ "11B2DCDE494A5F485E5BCA4BD88A2763AED1CA2B2FA8F0540678CD1E0F3AD80892" #define BP512R1_N \ "AADD9DB8DBE9C48B3FD4E6AE33C9FC07CB308DB3B3C9D20ED6639CCA703308" \ "70553E5C414CA92619418661197FAC10471DB1D381085DDADDB58796829CA90069" #if defined(POLARSSL_ECP_NIST_OPTIM) /* Forward declarations */ static int ecp_mod_p192( mpi * ); static int ecp_mod_p224( mpi * ); static int ecp_mod_p256( mpi * ); static int ecp_mod_p384( mpi * ); static int ecp_mod_p521( mpi * ); #endif /* * Set a group using well-known domain parameters */ int ecp_use_known_dp( ecp_group *grp, ecp_group_id id ) { grp->id = id; switch( id ) { #if defined(POLARSSL_ECP_DP_SECP192R1_ENABLED) case POLARSSL_ECP_DP_SECP192R1: #if defined(POLARSSL_ECP_NIST_OPTIM) grp->modp = ecp_mod_p192; #endif return( ecp_group_read_string( grp, 16, SECP192R1_P, SECP192R1_B, SECP192R1_GX, SECP192R1_GY, SECP192R1_N ) ); #endif /* POLARSSL_ECP_DP_SECP192R1_ENABLED */ #if defined(POLARSSL_ECP_DP_SECP224R1_ENABLED) case POLARSSL_ECP_DP_SECP224R1: #if defined(POLARSSL_ECP_NIST_OPTIM) grp->modp = ecp_mod_p224; #endif return( ecp_group_read_string( grp, 16, SECP224R1_P, SECP224R1_B, SECP224R1_GX, SECP224R1_GY, SECP224R1_N ) ); #endif /* POLARSSL_ECP_DP_SECP224R1_ENABLED */ #if defined(POLARSSL_ECP_DP_SECP256R1_ENABLED) case POLARSSL_ECP_DP_SECP256R1: #if defined(POLARSSL_ECP_NIST_OPTIM) grp->modp = ecp_mod_p256; #endif return( ecp_group_read_string( grp, 16, SECP256R1_P, SECP256R1_B, SECP256R1_GX, SECP256R1_GY, SECP256R1_N ) ); #endif /* POLARSSL_ECP_DP_SECP256R1_ENABLED */ #if defined(POLARSSL_ECP_DP_SECP384R1_ENABLED) case POLARSSL_ECP_DP_SECP384R1: #if defined(POLARSSL_ECP_NIST_OPTIM) grp->modp = ecp_mod_p384; #endif return( ecp_group_read_string( grp, 16, SECP384R1_P, SECP384R1_B, SECP384R1_GX, SECP384R1_GY, SECP384R1_N ) ); #endif /* POLARSSL_ECP_DP_SECP384R1_ENABLED */ #if defined(POLARSSL_ECP_DP_SECP521R1_ENABLED) case POLARSSL_ECP_DP_SECP521R1: #if defined(POLARSSL_ECP_NIST_OPTIM) grp->modp = ecp_mod_p521; #endif return( ecp_group_read_string( grp, 16, SECP521R1_P, SECP521R1_B, SECP521R1_GX, SECP521R1_GY, SECP521R1_N ) ); #endif /* POLARSSL_ECP_DP_SECP521R1_ENABLED */ #if defined(POLARSSL_ECP_DP_BP256R1_ENABLED) case POLARSSL_ECP_DP_BP256R1: return( ecp_group_read_string_gen( grp, 16, BP256R1_P, BP256R1_A, BP256R1_B, BP256R1_GX, BP256R1_GY, BP256R1_N ) ); #endif /* POLARSSL_ECP_DP_BP256R1_ENABLED */ #if defined(POLARSSL_ECP_DP_BP384R1_ENABLED) case POLARSSL_ECP_DP_BP384R1: return( ecp_group_read_string_gen( grp, 16, BP384R1_P, BP384R1_A, BP384R1_B, BP384R1_GX, BP384R1_GY, BP384R1_N ) ); #endif /* POLARSSL_ECP_DP_BP384R1_ENABLED */ #if defined(POLARSSL_ECP_DP_BP512R1_ENABLED) case POLARSSL_ECP_DP_BP512R1: return( ecp_group_read_string_gen( grp, 16, BP512R1_P, BP512R1_A, BP512R1_B, BP512R1_GX, BP512R1_GY, BP512R1_N ) ); #endif /* POLARSSL_ECP_DP_BP512R1_ENABLED */ default: ecp_group_free( grp ); return( POLARSSL_ERR_ECP_FEATURE_UNAVAILABLE ); } } /* * Set a group from an ECParameters record (RFC 4492) */ int ecp_tls_read_group( ecp_group *grp, const unsigned char **buf, size_t len ) { uint16_t tls_id; const ecp_curve_info *curve_info; /* * We expect at least three bytes (see below) */ if( len < 3 ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); /* * First byte is curve_type; only named_curve is handled */ if( *(*buf)++ != POLARSSL_ECP_TLS_NAMED_CURVE ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); /* * Next two bytes are the namedcurve value */ tls_id = *(*buf)++; tls_id <<= 8; tls_id |= *(*buf)++; if( ( curve_info = ecp_curve_info_from_tls_id( tls_id ) ) == NULL ) return( POLARSSL_ERR_ECP_FEATURE_UNAVAILABLE ); return ecp_use_known_dp( grp, curve_info->grp_id ); } /* * Write the ECParameters record corresponding to a group (RFC 4492) */ int ecp_tls_write_group( const ecp_group *grp, size_t *olen, unsigned char *buf, size_t blen ) { const ecp_curve_info *curve_info; if( ( curve_info = ecp_curve_info_from_grp_id( grp->id ) ) == NULL ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); /* * We are going to write 3 bytes (see below) */ *olen = 3; if( blen < *olen ) return( POLARSSL_ERR_ECP_BUFFER_TOO_SMALL ); /* * First byte is curve_type, always named_curve */ *buf++ = POLARSSL_ECP_TLS_NAMED_CURVE; /* * Next two bytes are the namedcurve value */ buf[0] = curve_info->tls_id >> 8; buf[1] = curve_info->tls_id & 0xFF; return 0; } /* * Wrapper around fast quasi-modp functions, with fall-back to mpi_mod_mpi. * See the documentation of struct ecp_group. * * This function is in the critial loop for ecp_mul, so pay attention to perf. */ static int ecp_modp( mpi *N, const ecp_group *grp ) { int ret; if( grp->modp == NULL ) return( mpi_mod_mpi( N, N, &grp->P ) ); /* N->s < 0 is a much faster test, which fails only if N is 0 */ if( ( N->s < 0 && mpi_cmp_int( N, 0 ) != 0 ) || mpi_msb( N ) > 2 * grp->pbits ) { return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); } MPI_CHK( grp->modp( N ) ); /* N->s < 0 is a much faster test, which fails only if N is 0 */ while( N->s < 0 && mpi_cmp_int( N, 0 ) != 0 ) MPI_CHK( mpi_add_mpi( N, N, &grp->P ) ); while( mpi_cmp_mpi( N, &grp->P ) >= 0 ) /* we known P, N and the result are positive */ MPI_CHK( mpi_sub_abs( N, N, &grp->P ) ); cleanup: return( ret ); } /* * Fast mod-p functions expect their argument to be in the 0..p^2 range. * * In order to guarantee that, we need to ensure that operands of * mpi_mul_mpi are in the 0..p range. So, after each operation we will * bring the result back to this range. * * The following macros are shortcuts for doing that. */ /* * Reduce a mpi mod p in-place, general case, to use after mpi_mul_mpi */ #define MOD_MUL( N ) MPI_CHK( ecp_modp( &N, grp ) ) /* * Reduce a mpi mod p in-place, to use after mpi_sub_mpi * N->s < 0 is a very fast test, which fails only if N is 0 */ #define MOD_SUB( N ) \ while( N.s < 0 && mpi_cmp_int( &N, 0 ) != 0 ) \ MPI_CHK( mpi_add_mpi( &N, &N, &grp->P ) ) /* * Reduce a mpi mod p in-place, to use after mpi_add_mpi and mpi_mul_int. * We known P, N and the result are positive, so sub_abs is correct, and * a bit faster. */ #define MOD_ADD( N ) \ while( mpi_cmp_mpi( &N, &grp->P ) >= 0 ) \ MPI_CHK( mpi_sub_abs( &N, &N, &grp->P ) ) /* * Normalize jacobian coordinates so that Z == 0 || Z == 1 (GECC 3.2.1) */ static int ecp_normalize( const ecp_group *grp, ecp_point *pt ) { int ret; mpi Zi, ZZi; if( mpi_cmp_int( &pt->Z, 0 ) == 0 ) return( 0 ); mpi_init( &Zi ); mpi_init( &ZZi ); /* * X = X / Z^2 mod p */ MPI_CHK( mpi_inv_mod( &Zi, &pt->Z, &grp->P ) ); MPI_CHK( mpi_mul_mpi( &ZZi, &Zi, &Zi ) ); MOD_MUL( ZZi ); MPI_CHK( mpi_mul_mpi( &pt->X, &pt->X, &ZZi ) ); MOD_MUL( pt->X ); /* * Y = Y / Z^3 mod p */ MPI_CHK( mpi_mul_mpi( &pt->Y, &pt->Y, &ZZi ) ); MOD_MUL( pt->Y ); MPI_CHK( mpi_mul_mpi( &pt->Y, &pt->Y, &Zi ) ); MOD_MUL( pt->Y ); /* * Z = 1 */ MPI_CHK( mpi_lset( &pt->Z, 1 ) ); cleanup: mpi_free( &Zi ); mpi_free( &ZZi ); return( ret ); } /* * Normalize jacobian coordinates of an array of points, * using Montgomery's trick to perform only one inversion mod P. * (See for example Cohen's "A Course in Computational Algebraic Number * Theory", Algorithm 10.3.4.) * * Warning: fails (returning an error) if one of the points is zero! * This should never happen, see choice of w in ecp_mul(). */ static int ecp_normalize_many( const ecp_group *grp, ecp_point T[], size_t t_len ) { int ret; size_t i; mpi *c, u, Zi, ZZi; if( t_len < 2 ) return( ecp_normalize( grp, T ) ); if( ( c = (mpi *) polarssl_malloc( t_len * sizeof( mpi ) ) ) == NULL ) return( POLARSSL_ERR_ECP_MALLOC_FAILED ); mpi_init( &u ); mpi_init( &Zi ); mpi_init( &ZZi ); for( i = 0; i < t_len; i++ ) mpi_init( &c[i] ); /* * c[i] = Z_0 * ... * Z_i */ MPI_CHK( mpi_copy( &c[0], &T[0].Z ) ); for( i = 1; i < t_len; i++ ) { MPI_CHK( mpi_mul_mpi( &c[i], &c[i-1], &T[i].Z ) ); MOD_MUL( c[i] ); } /* * u = 1 / (Z_0 * ... * Z_n) mod P */ MPI_CHK( mpi_inv_mod( &u, &c[t_len-1], &grp->P ) ); for( i = t_len - 1; ; i-- ) { /* * Zi = 1 / Z_i mod p * u = 1 / (Z_0 * ... * Z_i) mod P */ if( i == 0 ) { MPI_CHK( mpi_copy( &Zi, &u ) ); } else { MPI_CHK( mpi_mul_mpi( &Zi, &u, &c[i-1] ) ); MOD_MUL( Zi ); MPI_CHK( mpi_mul_mpi( &u, &u, &T[i].Z ) ); MOD_MUL( u ); } /* * proceed as in normalize() */ MPI_CHK( mpi_mul_mpi( &ZZi, &Zi, &Zi ) ); MOD_MUL( ZZi ); MPI_CHK( mpi_mul_mpi( &T[i].X, &T[i].X, &ZZi ) ); MOD_MUL( T[i].X ); MPI_CHK( mpi_mul_mpi( &T[i].Y, &T[i].Y, &ZZi ) ); MOD_MUL( T[i].Y ); MPI_CHK( mpi_mul_mpi( &T[i].Y, &T[i].Y, &Zi ) ); MOD_MUL( T[i].Y ); MPI_CHK( mpi_lset( &T[i].Z, 1 ) ); if( i == 0 ) break; } cleanup: mpi_free( &u ); mpi_free( &Zi ); mpi_free( &ZZi ); for( i = 0; i < t_len; i++ ) mpi_free( &c[i] ); polarssl_free( c ); return( ret ); } /* * Point doubling R = 2 P, Jacobian coordinates * * http://www.hyperelliptic.org/EFD/g1p/auto-code/shortw/jacobian/doubling/dbl-2007-bl.op3 * with heavy variable renaming, some reordering and one minor modification * (a = 2 * b, c = d - 2a replaced with c = d, c = c - b, c = c - b) * in order to use a lot less intermediate variables (6 vs 25). */ static int ecp_double_jac( const ecp_group *grp, ecp_point *R, const ecp_point *P ) { int ret; mpi T1, T2, T3, X3, Y3, Z3; #if defined(POLARSSL_SELF_TEST) dbl_count++; #endif mpi_init( &T1 ); mpi_init( &T2 ); mpi_init( &T3 ); mpi_init( &X3 ); mpi_init( &Y3 ); mpi_init( &Z3 ); MPI_CHK( mpi_mul_mpi( &T3, &P->X, &P->X ) ); MOD_MUL( T3 ); MPI_CHK( mpi_mul_mpi( &T2, &P->Y, &P->Y ) ); MOD_MUL( T2 ); MPI_CHK( mpi_mul_mpi( &Y3, &T2, &T2 ) ); MOD_MUL( Y3 ); MPI_CHK( mpi_add_mpi( &X3, &P->X, &T2 ) ); MOD_ADD( X3 ); MPI_CHK( mpi_mul_mpi( &X3, &X3, &X3 ) ); MOD_MUL( X3 ); MPI_CHK( mpi_sub_mpi( &X3, &X3, &Y3 ) ); MOD_SUB( X3 ); MPI_CHK( mpi_sub_mpi( &X3, &X3, &T3 ) ); MOD_SUB( X3 ); MPI_CHK( mpi_mul_int( &T1, &X3, 2 ) ); MOD_ADD( T1 ); MPI_CHK( mpi_mul_mpi( &Z3, &P->Z, &P->Z ) ); MOD_MUL( Z3 ); MPI_CHK( mpi_mul_mpi( &X3, &Z3, &Z3 ) ); MOD_MUL( X3 ); MPI_CHK( mpi_mul_int( &T3, &T3, 3 ) ); MOD_ADD( T3 ); MPI_CHK( mpi_mul_mpi( &X3, &X3, &grp->A ) ); MOD_MUL( X3 ); MPI_CHK( mpi_add_mpi( &T3, &T3, &X3 ) ); MOD_ADD( T3 ); MPI_CHK( mpi_mul_mpi( &X3, &T3, &T3 ) ); MOD_MUL( X3 ); MPI_CHK( mpi_sub_mpi( &X3, &X3, &T1 ) ); MOD_SUB( X3 ); MPI_CHK( mpi_sub_mpi( &X3, &X3, &T1 ) ); MOD_SUB( X3 ); MPI_CHK( mpi_sub_mpi( &T1, &T1, &X3 ) ); MOD_SUB( T1 ); MPI_CHK( mpi_mul_mpi( &T1, &T3, &T1 ) ); MOD_MUL( T1 ); MPI_CHK( mpi_mul_int( &T3, &Y3, 8 ) ); MOD_ADD( T3 ); MPI_CHK( mpi_sub_mpi( &Y3, &T1, &T3 ) ); MOD_SUB( Y3 ); MPI_CHK( mpi_add_mpi( &T1, &P->Y, &P->Z ) ); MOD_ADD( T1 ); MPI_CHK( mpi_mul_mpi( &T1, &T1, &T1 ) ); MOD_MUL( T1 ); MPI_CHK( mpi_sub_mpi( &T1, &T1, &T2 ) ); MOD_SUB( T1 ); MPI_CHK( mpi_sub_mpi( &Z3, &T1, &Z3 ) ); MOD_SUB( Z3 ); MPI_CHK( mpi_copy( &R->X, &X3 ) ); MPI_CHK( mpi_copy( &R->Y, &Y3 ) ); MPI_CHK( mpi_copy( &R->Z, &Z3 ) ); cleanup: mpi_free( &T1 ); mpi_free( &T2 ); mpi_free( &T3 ); mpi_free( &X3 ); mpi_free( &Y3 ); mpi_free( &Z3 ); return( ret ); } /* * Addition or subtraction: R = P + Q or R = P - Q, * mixed affine-Jacobian coordinates (GECC 3.22) * * The coordinates of Q must be normalized (= affine), * but those of P don't need to. R is not normalized. * * If sign >= 0, perform addition, otherwise perform subtraction, * taking advantage of the fact that, for Q != 0, we have * -Q = (Q.X, -Q.Y, Q.Z) */ static int ecp_add_mixed( const ecp_group *grp, ecp_point *R, const ecp_point *P, const ecp_point *Q, signed char sign ) { int ret; mpi T1, T2, T3, T4, X, Y, Z; #if defined(POLARSSL_SELF_TEST) add_count++; #endif /* * Trivial cases: P == 0 or Q == 0 * (Check Q first, so that we know Q != 0 when we compute -Q.) */ if( mpi_cmp_int( &Q->Z, 0 ) == 0 ) return( ecp_copy( R, P ) ); if( mpi_cmp_int( &P->Z, 0 ) == 0 ) { ret = ecp_copy( R, Q ); /* * -R.Y mod P = P - R.Y unless R.Y == 0 */ if( ret == 0 && sign < 0) if( mpi_cmp_int( &R->Y, 0 ) != 0 ) ret = mpi_sub_mpi( &R->Y, &grp->P, &R->Y ); return( ret ); } /* * Make sure Q coordinates are normalized */ if( mpi_cmp_int( &Q->Z, 1 ) != 0 ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); mpi_init( &T1 ); mpi_init( &T2 ); mpi_init( &T3 ); mpi_init( &T4 ); mpi_init( &X ); mpi_init( &Y ); mpi_init( &Z ); MPI_CHK( mpi_mul_mpi( &T1, &P->Z, &P->Z ) ); MOD_MUL( T1 ); MPI_CHK( mpi_mul_mpi( &T2, &T1, &P->Z ) ); MOD_MUL( T2 ); MPI_CHK( mpi_mul_mpi( &T1, &T1, &Q->X ) ); MOD_MUL( T1 ); MPI_CHK( mpi_mul_mpi( &T2, &T2, &Q->Y ) ); MOD_MUL( T2 ); /* * For subtraction, -Q.Y should have been used instead of Q.Y, * so we replace T2 by -T2, which is P - T2 mod P */ if( sign < 0 ) { MPI_CHK( mpi_sub_mpi( &T2, &grp->P, &T2 ) ); MOD_SUB( T2 ); } MPI_CHK( mpi_sub_mpi( &T1, &T1, &P->X ) ); MOD_SUB( T1 ); MPI_CHK( mpi_sub_mpi( &T2, &T2, &P->Y ) ); MOD_SUB( T2 ); if( mpi_cmp_int( &T1, 0 ) == 0 ) { if( mpi_cmp_int( &T2, 0 ) == 0 ) { ret = ecp_double_jac( grp, R, P ); goto cleanup; } else { ret = ecp_set_zero( R ); goto cleanup; } } MPI_CHK( mpi_mul_mpi( &Z, &P->Z, &T1 ) ); MOD_MUL( Z ); MPI_CHK( mpi_mul_mpi( &T3, &T1, &T1 ) ); MOD_MUL( T3 ); MPI_CHK( mpi_mul_mpi( &T4, &T3, &T1 ) ); MOD_MUL( T4 ); MPI_CHK( mpi_mul_mpi( &T3, &T3, &P->X ) ); MOD_MUL( T3 ); MPI_CHK( mpi_mul_int( &T1, &T3, 2 ) ); MOD_ADD( T1 ); MPI_CHK( mpi_mul_mpi( &X, &T2, &T2 ) ); MOD_MUL( X ); MPI_CHK( mpi_sub_mpi( &X, &X, &T1 ) ); MOD_SUB( X ); MPI_CHK( mpi_sub_mpi( &X, &X, &T4 ) ); MOD_SUB( X ); MPI_CHK( mpi_sub_mpi( &T3, &T3, &X ) ); MOD_SUB( T3 ); MPI_CHK( mpi_mul_mpi( &T3, &T3, &T2 ) ); MOD_MUL( T3 ); MPI_CHK( mpi_mul_mpi( &T4, &T4, &P->Y ) ); MOD_MUL( T4 ); MPI_CHK( mpi_sub_mpi( &Y, &T3, &T4 ) ); MOD_SUB( Y ); MPI_CHK( mpi_copy( &R->X, &X ) ); MPI_CHK( mpi_copy( &R->Y, &Y ) ); MPI_CHK( mpi_copy( &R->Z, &Z ) ); cleanup: mpi_free( &T1 ); mpi_free( &T2 ); mpi_free( &T3 ); mpi_free( &T4 ); mpi_free( &X ); mpi_free( &Y ); mpi_free( &Z ); return( ret ); } /* * Addition: R = P + Q, result's coordinates normalized */ int ecp_add( const ecp_group *grp, ecp_point *R, const ecp_point *P, const ecp_point *Q ) { int ret; MPI_CHK( ecp_add_mixed( grp, R, P, Q , 1 ) ); MPI_CHK( ecp_normalize( grp, R ) ); cleanup: return( ret ); } /* * Subtraction: R = P - Q, result's coordinates normalized */ int ecp_sub( const ecp_group *grp, ecp_point *R, const ecp_point *P, const ecp_point *Q ) { int ret; MPI_CHK( ecp_add_mixed( grp, R, P, Q, -1 ) ); MPI_CHK( ecp_normalize( grp, R ) ); cleanup: return( ret ); } /* * Compute a modified width-w non-adjacent form (NAF) of a number, * with a fixed pattern for resistance to simple timing attacks (even SPA), * see [1]. (The resulting multiplication algorithm can also been seen as a * modification of 2^w-ary multiplication, with signed coefficients, all of * them odd.) * * Input: * m must be an odd positive mpi less than w * k bits long * x must be an array of k elements * w must be less than a certain maximum (currently 8) * * The result is a sequence x[0], ..., x[k-1] with x[i] in the range * - 2^(width - 1) .. 2^(width - 1) - 1 such that * m = (2 * x[0] + 1) + 2^width * (2 * x[1] + 1) + ... * + 2^((k-1) * width) * (2 * x[k-1] + 1) * * Compared to "Algorithm SPA-resistant Width-w NAF with Odd Scalar" * p. 335 of the cited reference, here we return only u, not d_w since * it is known that the other d_w[j] will be 0. Moreover, the returned * string doesn't actually store u_i but x_i = u_i / 2 since it is known * that u_i is odd. Also, since we always select a positive value for d * mod 2^w, we don't need to check the sign of u[i-1] when the reference * does. Finally, there is an off-by-one error in the reference: the * last index should be k-1, not k. */ static int ecp_w_naf_fixed( signed char x[], size_t k, unsigned char w, const mpi *m ) { int ret; unsigned int i, u, mask, carry; mpi M; mpi_init( &M ); MPI_CHK( mpi_copy( &M, m ) ); mask = ( 1 << w ) - 1; carry = 1 << ( w - 1 ); for( i = 0; i < k; i++ ) { u = M.p[0] & mask; if( ( u & 1 ) == 0 && i > 0 ) x[i - 1] -= carry; x[i] = u >> 1; mpi_shift_r( &M, w ); } /* * We should have consumed all bits, unless the input value was too big */ if( mpi_cmp_int( &M, 0 ) != 0 ) ret = POLARSSL_ERR_ECP_BAD_INPUT_DATA; cleanup: mpi_free( &M ); return( ret ); } /* * Precompute odd multiples of P up to (2 * t_len - 1) P. * The table is filled with T[i] = (2 * i + 1) P. */ static int ecp_precompute( const ecp_group *grp, ecp_point T[], size_t t_len, const ecp_point *P ) { int ret; size_t i; ecp_point PP; ecp_point_init( &PP ); MPI_CHK( ecp_add( grp, &PP, P, P ) ); MPI_CHK( ecp_copy( &T[0], P ) ); for( i = 1; i < t_len; i++ ) MPI_CHK( ecp_add_mixed( grp, &T[i], &T[i-1], &PP, +1 ) ); /* * T[0] = P already has normalized coordinates */ MPI_CHK( ecp_normalize_many( grp, T + 1, t_len - 1 ) ); cleanup: ecp_point_free( &PP ); return( ret ); } /* * Randomize jacobian coordinates: * (X, Y, Z) -> (l^2 X, l^3 Y, l Z) for random l * This is sort of the reverse operation of ecp_normalize(). */ static int ecp_randomize_coordinates( const ecp_group *grp, ecp_point *pt, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { int ret; mpi l, ll; size_t p_size = (grp->pbits + 7) / 8; int count = 0; mpi_init( &l ); mpi_init( &ll ); /* Generate l such that 1 < l < p */ do { mpi_fill_random( &l, p_size, f_rng, p_rng ); while( mpi_cmp_mpi( &l, &grp->P ) >= 0 ) mpi_shift_r( &l, 1 ); if( count++ > 10 ) return( POLARSSL_ERR_ECP_RANDOM_FAILED ); } while( mpi_cmp_int( &l, 1 ) <= 0 ); /* Z = l * Z */ MPI_CHK( mpi_mul_mpi( &pt->Z, &pt->Z, &l ) ); MOD_MUL( pt->Z ); /* X = l^2 * X */ MPI_CHK( mpi_mul_mpi( &ll, &l, &l ) ); MOD_MUL( ll ); MPI_CHK( mpi_mul_mpi( &pt->X, &pt->X, &ll ) ); MOD_MUL( pt->X ); /* Y = l^3 * Y */ MPI_CHK( mpi_mul_mpi( &ll, &ll, &l ) ); MOD_MUL( ll ); MPI_CHK( mpi_mul_mpi( &pt->Y, &pt->Y, &ll ) ); MOD_MUL( pt->Y ); cleanup: mpi_free( &l ); mpi_free( &ll ); return( ret ); } /* * Maximum length of the precomputed table */ #define MAX_PRE_LEN ( 1 << (POLARSSL_ECP_WINDOW_SIZE - 1) ) /* * Maximum length of the NAF: ceil( grp->nbits + 1 ) / w * (that is: grp->nbits / w + 1) * Allow p_bits + 1 bits in case M = grp->N + 1 is one bit longer than N. */ #define MAX_NAF_LEN ( POLARSSL_ECP_MAX_BITS / 2 + 1 ) /* * Integer multiplication: R = m * P * * Based on fixed-pattern width-w NAF, see comments of ecp_w_naf_fixed(). * * This function executes a fixed number of operations for * random m in the range 0 .. 2^nbits - 1. * * As an additional countermeasure against potential timing attacks, * we randomize coordinates before each addition. This was suggested as a * countermeasure against DPA in 5.3 of [2] (with the obvious adaptation that * we use jacobian coordinates, not standard projective coordinates). */ int ecp_mul( ecp_group *grp, ecp_point *R, const mpi *m, const ecp_point *P, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { int ret; unsigned char w, m_is_odd, p_eq_g; size_t pre_len = 1, naf_len, i, j; signed char naf[ MAX_NAF_LEN ]; ecp_point Q, *T = NULL, S[2]; mpi M; if( mpi_cmp_int( m, 0 ) < 0 || mpi_msb( m ) > grp->nbits ) return( POLARSSL_ERR_ECP_BAD_INPUT_DATA ); mpi_init( &M ); ecp_point_init( &Q ); ecp_point_init( &S[0] ); ecp_point_init( &S[1] ); /* * Check if P == G */ p_eq_g = ( mpi_cmp_int( &P->Z, 1 ) == 0 && mpi_cmp_mpi( &P->Y, &grp->G.Y ) == 0 && mpi_cmp_mpi( &P->X, &grp->G.X ) == 0 ); /* * If P == G, pre-compute a lot of points: this will be re-used later, * otherwise, choose window size depending on curve size */ if( p_eq_g ) w = POLARSSL_ECP_WINDOW_SIZE; else w = grp->nbits >= 512 ? 6 : grp->nbits >= 224 ? 5 : 4; /* * Make sure w is within the limits. * The last test ensures that none of the precomputed points is zero, * which wouldn't be handled correctly by ecp_normalize_many(). * It is only useful for very small curves as used in the test suite. */ if( w > POLARSSL_ECP_WINDOW_SIZE ) w = POLARSSL_ECP_WINDOW_SIZE; if( w < 2 || w >= grp->nbits ) w = 2; pre_len <<= ( w - 1 ); naf_len = grp->nbits / w + 1; /* * Prepare precomputed points: if P == G we want to * use grp->T if already initialized, or initiliaze it. */ if( ! p_eq_g || grp->T == NULL ) { T = (ecp_point *) polarssl_malloc( pre_len * sizeof( ecp_point ) ); if( T == NULL ) { ret = POLARSSL_ERR_ECP_MALLOC_FAILED; goto cleanup; } for( i = 0; i < pre_len; i++ ) ecp_point_init( &T[i] ); MPI_CHK( ecp_precompute( grp, T, pre_len, P ) ); if( p_eq_g ) { grp->T = T; grp->T_size = pre_len; } } else { T = grp->T; /* Should never happen, but we want to be extra sure */ if( pre_len != grp->T_size ) { ret = POLARSSL_ERR_ECP_BAD_INPUT_DATA; goto cleanup; } } /* * Make sure M is odd (M = m + 1 or M = m + 2) * later we'll get m * P by subtracting P or 2 * P to M * P. */ m_is_odd = ( mpi_get_bit( m, 0 ) == 1 ); MPI_CHK( mpi_copy( &M, m ) ); MPI_CHK( mpi_add_int( &M, &M, 1 + m_is_odd ) ); /* * Compute the fixed-pattern NAF of M */ MPI_CHK( ecp_w_naf_fixed( naf, naf_len, w, &M ) ); /* * Compute M * P, using a variant of left-to-right 2^w-ary multiplication: * at each step we add (2 * naf[i] + 1) P, then multiply by 2^w. * * If naf[i] >= 0, we have (2 * naf[i] + 1) P == T[ naf[i] ] * Otherwise, (2 * naf[i] + 1) P == - ( 2 * ( - naf[i] - 1 ) + 1) P * == T[ - naf[i] - 1 ] */ MPI_CHK( ecp_set_zero( &Q ) ); i = naf_len - 1; while( 1 ) { /* Countermeasure (see comments above) */ if( f_rng != NULL ) ecp_randomize_coordinates( grp, &Q, f_rng, p_rng ); if( naf[i] < 0 ) { MPI_CHK( ecp_add_mixed( grp, &Q, &Q, &T[ - naf[i] - 1 ], -1 ) ); } else { MPI_CHK( ecp_add_mixed( grp, &Q, &Q, &T[ naf[i] ], +1 ) ); } if( i == 0 ) break; i--; for( j = 0; j < w; j++ ) { MPI_CHK( ecp_double_jac( grp, &Q, &Q ) ); } } /* * Now get m * P from M * P */ MPI_CHK( ecp_copy( &S[0], P ) ); MPI_CHK( ecp_add( grp, &S[1], P, P ) ); MPI_CHK( ecp_sub( grp, R, &Q, &S[m_is_odd] ) ); cleanup: if( T != NULL && ! p_eq_g ) { for( i = 0; i < pre_len; i++ ) ecp_point_free( &T[i] ); polarssl_free( T ); } ecp_point_free( &S[1] ); ecp_point_free( &S[0] ); ecp_point_free( &Q ); mpi_free( &M ); return( ret ); } /* * Check that a point is valid as a public key (SEC1 3.2.3.1) */ int ecp_check_pubkey( const ecp_group *grp, const ecp_point *pt ) { int ret; mpi YY, RHS; if( mpi_cmp_int( &pt->Z, 0 ) == 0 ) return( POLARSSL_ERR_ECP_INVALID_KEY ); /* * pt coordinates must be normalized for our checks */ if( mpi_cmp_int( &pt->Z, 1 ) != 0 ) return( POLARSSL_ERR_ECP_INVALID_KEY ); if( mpi_cmp_int( &pt->X, 0 ) < 0 || mpi_cmp_int( &pt->Y, 0 ) < 0 || mpi_cmp_mpi( &pt->X, &grp->P ) >= 0 || mpi_cmp_mpi( &pt->Y, &grp->P ) >= 0 ) return( POLARSSL_ERR_ECP_INVALID_KEY ); mpi_init( &YY ); mpi_init( &RHS ); /* * YY = Y^2 * RHS = X (X^2 + A) + B = X^3 + A X + B */ MPI_CHK( mpi_mul_mpi( &YY, &pt->Y, &pt->Y ) ); MOD_MUL( YY ); MPI_CHK( mpi_mul_mpi( &RHS, &pt->X, &pt->X ) ); MOD_MUL( RHS ); MPI_CHK( mpi_add_mpi( &RHS, &RHS, &grp->A ) ); MOD_ADD( RHS ); MPI_CHK( mpi_mul_mpi( &RHS, &RHS, &pt->X ) ); MOD_MUL( RHS ); MPI_CHK( mpi_add_mpi( &RHS, &RHS, &grp->B ) ); MOD_ADD( RHS ); if( mpi_cmp_mpi( &YY, &RHS ) != 0 ) ret = POLARSSL_ERR_ECP_INVALID_KEY; cleanup: mpi_free( &YY ); mpi_free( &RHS ); return( ret ); } /* * Check that an mpi is valid as a private key (SEC1 3.2) */ int ecp_check_privkey( const ecp_group *grp, const mpi *d ) { /* We want 1 <= d <= N-1 */ if ( mpi_cmp_int( d, 1 ) < 0 || mpi_cmp_mpi( d, &grp->N ) >= 0 ) return( POLARSSL_ERR_ECP_INVALID_KEY ); return( 0 ); } /* * Generate a keypair (SEC1 3.2.1) */ int ecp_gen_keypair( ecp_group *grp, mpi *d, ecp_point *Q, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { int count = 0; size_t n_size = (grp->nbits + 7) / 8; /* * Generate d such that 1 <= n < N */ do { mpi_fill_random( d, n_size, f_rng, p_rng ); while( mpi_cmp_mpi( d, &grp->N ) >= 0 ) mpi_shift_r( d, 1 ); if( count++ > 10 ) return( POLARSSL_ERR_ECP_RANDOM_FAILED ); } while( mpi_cmp_int( d, 1 ) < 0 ); return( ecp_mul( grp, Q, d, &grp->G, f_rng, p_rng ) ); } #if defined(POLARSSL_ECP_NIST_OPTIM) /* * Fast reduction modulo the primes used by the NIST curves. * * These functions are: critical for speed, but not need for correct * operations. So, we make the choice to heavily rely on the internals of our * bignum library, which creates a tight coupling between these functions and * our MPI implementation. However, the coupling between the ECP module and * MPI remains loose, since these functions can be deactivated at will. */ #if defined(POLARSSL_ECP_DP_SECP192R1_ENABLED) /* * Compared to the way things are presented in FIPS 186-3 D.2, * we proceed in columns, from right (least significant chunk) to left, * adding chunks to N in place, and keeping a carry for the next chunk. * This avoids moving things around in memory, and uselessly adding zeros, * compared to the more straightforward, line-oriented approach. * * For this prime we need to handle data in chunks of 64 bits. * Since this is always a multiple of our basic t_uint, we can * use a t_uint * to designate such a chunk, and small loops to handle it. */ /* Add 64-bit chunks (dst += src) and update carry */ static inline void add64( t_uint *dst, t_uint *src, t_uint *carry ) { unsigned char i; t_uint c = 0; for( i = 0; i < 8 / sizeof( t_uint ); i++, dst++, src++ ) { *dst += c; c = ( *dst < c ); *dst += *src; c += ( *dst < *src ); } *carry += c; } /* Add carry to a 64-bit chunk and update carry */ static inline void carry64( t_uint *dst, t_uint *carry ) { unsigned char i; for( i = 0; i < 8 / sizeof( t_uint ); i++, dst++ ) { *dst += *carry; *carry = ( *dst < *carry ); } } #define WIDTH 8 / sizeof( t_uint ) #define A( i ) N->p + i * WIDTH #define ADD( i ) add64( p, A( i ), &c ) #define NEXT p += WIDTH; carry64( p, &c ) #define LAST p += WIDTH; *p = c; while( ++p < end ) *p = 0 /* * Fast quasi-reduction modulo p192 (FIPS 186-3 D.2.1) */ static int ecp_mod_p192( mpi *N ) { int ret; t_uint c = 0; t_uint *p, *end; /* Make sure we have enough blocks so that A(5) is legal */ MPI_CHK( mpi_grow( N, 6 * WIDTH ) ); p = N->p; end = p + N->n; ADD( 3 ); ADD( 5 ); NEXT; // A0 += A3 + A5 ADD( 3 ); ADD( 4 ); ADD( 5 ); NEXT; // A1 += A3 + A4 + A5 ADD( 4 ); ADD( 5 ); LAST; // A2 += A4 + A5 cleanup: return( ret ); } #undef WIDTH #undef A #undef ADD #undef NEXT #undef LAST #endif /* POLARSSL_ECP_DP_SECP192R1_ENABLED */ #if defined(POLARSSL_ECP_DP_SECP224R1_ENABLED) || \ defined(POLARSSL_ECP_DP_SECP256R1_ENABLED) || \ defined(POLARSSL_ECP_DP_SECP384R1_ENABLED) /* * The reader is advised to first understand ecp_mod_p192() since the same * general structure is used here, but with additional complications: * (1) chunks of 32 bits, and (2) subtractions. */ /* * For these primes, we need to handle data in chunks of 32 bits. * This makes it more complicated if we use 64 bits limbs in MPI, * which prevents us from using a uniform access method as for p192. * * So, we define a mini abstraction layer to access 32 bit chunks, * load them in 'cur' for work, and store them back from 'cur' when done. * * While at it, also define the size of N in terms of 32-bit chunks. */ #define LOAD32 cur = A( i ); #if defined(POLARSSL_HAVE_INT8) /* 8 bit */ #define MAX32 N->n / 4 #define A( j ) (uint32_t)( N->p[4*j+0] ) | \ ( N->p[4*j+1] << 8 ) | \ ( N->p[4*j+2] << 16 ) | \ ( N->p[4*j+3] << 24 ) #define STORE32 N->p[4*i+0] = (uint8_t)( cur ); \ N->p[4*i+1] = (uint8_t)( cur >> 8 ); \ N->p[4*i+2] = (uint8_t)( cur >> 16 ); \ N->p[4*i+3] = (uint8_t)( cur >> 24 ); #elif defined(POLARSSL_HAVE_INT16) /* 16 bit */ #define MAX32 N->n / 2 #define A( j ) (uint32_t)( N->p[2*j] ) | ( N->p[2*j+1] << 16 ) #define STORE32 N->p[2*i+0] = (uint16_t)( cur ); \ N->p[2*i+1] = (uint16_t)( cur >> 16 ); #elif defined(POLARSSL_HAVE_INT32) /* 32 bit */ #define MAX32 N->n #define A( j ) N->p[j] #define STORE32 N->p[i] = cur; #else /* 64-bit */ #define MAX32 N->n * 2 #define A( j ) j % 2 ? (uint32_t)( N->p[j/2] >> 32 ) : (uint32_t)( N->p[j/2] ) #define STORE32 \ if( i % 2 ) { \ N->p[i/2] &= 0x00000000FFFFFFFF; \ N->p[i/2] |= ((uint64_t) cur) << 32; \ } else { \ N->p[i/2] &= 0xFFFFFFFF00000000; \ N->p[i/2] |= (uint64_t) cur; \ } #endif /* sizeof( t_uint ) */ /* * Helpers for addition and subtraction of chunks, with signed carry. */ static inline void add32( uint32_t *dst, uint32_t src, signed char *carry ) { *dst += src; *carry += ( *dst < src ); } static inline void sub32( uint32_t *dst, uint32_t src, signed char *carry ) { *carry -= ( *dst < src ); *dst -= src; } #define ADD( j ) add32( &cur, A( j ), &c ); #define SUB( j ) sub32( &cur, A( j ), &c ); /* * Helpers for the main 'loop' * (see fix_negative for the motivation of C) */ #define INIT( b ) \ int ret; \ signed char c = 0, cc; \ uint32_t cur; \ size_t i = 0, bits = b; \ mpi C; \ t_uint Cp[ b / 8 / sizeof( t_uint) + 1 ]; \ \ C.s = 1; \ C.n = b / 8 / sizeof( t_uint) + 1; \ C.p = Cp; \ memset( Cp, 0, C.n * sizeof( t_uint ) ); \ \ MPI_CHK( mpi_grow( N, b * 2 / 8 / sizeof( t_uint ) ) ); \ LOAD32; #define NEXT \ STORE32; i++; LOAD32; \ cc = c; c = 0; \ if( cc < 0 ) \ sub32( &cur, -cc, &c ); \ else \ add32( &cur, cc, &c ); \ #define LAST \ STORE32; i++; \ cur = c > 0 ? c : 0; STORE32; \ cur = 0; while( ++i < MAX32 ) { STORE32; } \ if( c < 0 ) fix_negative( N, c, &C, bits ); /* * If the result is negative, we get it in the form * c * 2^(bits + 32) + N, with c negative and N positive shorter than 'bits' */ static inline int fix_negative( mpi *N, signed char c, mpi *C, size_t bits ) { int ret; /* C = - c * 2^(bits + 32) */ #if !defined(POLARSSL_HAVE_INT64) ((void) bits); #else if( bits == 224 ) C->p[ C->n - 1 ] = ((t_uint) -c) << 32; else #endif C->p[ C->n - 1 ] = (t_uint) -c; /* N = - ( C - N ) */ MPI_CHK( mpi_sub_abs( N, C, N ) ); N->s = -1; cleanup: return( ret ); } #if defined(POLARSSL_ECP_DP_SECP224R1_ENABLED) /* * Fast quasi-reduction modulo p224 (FIPS 186-3 D.2.2) */ static int ecp_mod_p224( mpi *N ) { INIT( 224 ); SUB( 7 ); SUB( 11 ); NEXT; // A0 += -A7 - A11 SUB( 8 ); SUB( 12 ); NEXT; // A1 += -A8 - A12 SUB( 9 ); SUB( 13 ); NEXT; // A2 += -A9 - A13 SUB( 10 ); ADD( 7 ); ADD( 11 ); NEXT; // A3 += -A10 + A7 + A11 SUB( 11 ); ADD( 8 ); ADD( 12 ); NEXT; // A4 += -A11 + A8 + A12 SUB( 12 ); ADD( 9 ); ADD( 13 ); NEXT; // A5 += -A12 + A9 + A13 SUB( 13 ); ADD( 10 ); LAST; // A6 += -A13 + A10 cleanup: return( ret ); } #endif /* POLARSSL_ECP_DP_SECP224R1_ENABLED */ #if defined(POLARSSL_ECP_DP_SECP256R1_ENABLED) /* * Fast quasi-reduction modulo p256 (FIPS 186-3 D.2.3) */ static int ecp_mod_p256( mpi *N ) { INIT( 256 ); ADD( 8 ); ADD( 9 ); SUB( 11 ); SUB( 12 ); SUB( 13 ); SUB( 14 ); NEXT; // A0 ADD( 9 ); ADD( 10 ); SUB( 12 ); SUB( 13 ); SUB( 14 ); SUB( 15 ); NEXT; // A1 ADD( 10 ); ADD( 11 ); SUB( 13 ); SUB( 14 ); SUB( 15 ); NEXT; // A2 ADD( 11 ); ADD( 11 ); ADD( 12 ); ADD( 12 ); ADD( 13 ); SUB( 15 ); SUB( 8 ); SUB( 9 ); NEXT; // A3 ADD( 12 ); ADD( 12 ); ADD( 13 ); ADD( 13 ); ADD( 14 ); SUB( 9 ); SUB( 10 ); NEXT; // A4 ADD( 13 ); ADD( 13 ); ADD( 14 ); ADD( 14 ); ADD( 15 ); SUB( 10 ); SUB( 11 ); NEXT; // A5 ADD( 14 ); ADD( 14 ); ADD( 15 ); ADD( 15 ); ADD( 14 ); ADD( 13 ); SUB( 8 ); SUB( 9 ); NEXT; // A6 ADD( 15 ); ADD( 15 ); ADD( 15 ); ADD( 8 ); SUB( 10 ); SUB( 11 ); SUB( 12 ); SUB( 13 ); LAST; // A7 cleanup: return( ret ); } #endif /* POLARSSL_ECP_DP_SECP256R1_ENABLED */ #if defined(POLARSSL_ECP_DP_SECP384R1_ENABLED) /* * Fast quasi-reduction modulo p384 (FIPS 186-3 D.2.4) */ static int ecp_mod_p384( mpi *N ) { INIT( 384 ); ADD( 12 ); ADD( 21 ); ADD( 20 ); SUB( 23 ); NEXT; // A0 ADD( 13 ); ADD( 22 ); ADD( 23 ); SUB( 12 ); SUB( 20 ); NEXT; // A2 ADD( 14 ); ADD( 23 ); SUB( 13 ); SUB( 21 ); NEXT; // A2 ADD( 15 ); ADD( 12 ); ADD( 20 ); ADD( 21 ); SUB( 14 ); SUB( 22 ); SUB( 23 ); NEXT; // A3 ADD( 21 ); ADD( 21 ); ADD( 16 ); ADD( 13 ); ADD( 12 ); ADD( 20 ); ADD( 22 ); SUB( 15 ); SUB( 23 ); SUB( 23 ); NEXT; // A4 ADD( 22 ); ADD( 22 ); ADD( 17 ); ADD( 14 ); ADD( 13 ); ADD( 21 ); ADD( 23 ); SUB( 16 ); NEXT; // A5 ADD( 23 ); ADD( 23 ); ADD( 18 ); ADD( 15 ); ADD( 14 ); ADD( 22 ); SUB( 17 ); NEXT; // A6 ADD( 19 ); ADD( 16 ); ADD( 15 ); ADD( 23 ); SUB( 18 ); NEXT; // A7 ADD( 20 ); ADD( 17 ); ADD( 16 ); SUB( 19 ); NEXT; // A8 ADD( 21 ); ADD( 18 ); ADD( 17 ); SUB( 20 ); NEXT; // A9 ADD( 22 ); ADD( 19 ); ADD( 18 ); SUB( 21 ); NEXT; // A10 ADD( 23 ); ADD( 20 ); ADD( 19 ); SUB( 22 ); LAST; // A11 cleanup: return( ret ); } #endif /* POLARSSL_ECP_DP_SECP384R1_ENABLED */ #undef A #undef LOAD32 #undef STORE32 #undef MAX32 #undef INIT #undef NEXT #undef LAST #endif /* POLARSSL_ECP_DP_SECP224R1_ENABLED || POLARSSL_ECP_DP_SECP256R1_ENABLED || POLARSSL_ECP_DP_SECP384R1_ENABLED */ #if defined(POLARSSL_ECP_DP_SECP521R1_ENABLED) /* * Here we have an actual Mersenne prime, so things are more straightforward. * However, chunks are aligned on a 'weird' boundary (521 bits). */ /* Size of p521 in terms of t_uint */ #define P521_WIDTH ( 521 / 8 / sizeof( t_uint ) + 1 ) /* Bits to keep in the most significant t_uint */ #if defined(POLARSSL_HAVE_INT8) #define P521_MASK 0x01 #else #define P521_MASK 0x01FF #endif /* * Fast quasi-reduction modulo p521 (FIPS 186-3 D.2.5) * Write N as A1 + 2^521 A0, return A0 + A1 */ static int ecp_mod_p521( mpi *N ) { int ret; size_t i; mpi M; t_uint Mp[P521_WIDTH + 1]; /* Worst case for the size of M is when t_uint is 16 bits: * we need to hold bits 513 to 1056, which is 34 limbs, that is * P521_WIDTH + 1. Otherwise P521_WIDTH is enough. */ if( N->n < P521_WIDTH ) return( 0 ); /* M = A1 */ M.s = 1; M.n = N->n - ( P521_WIDTH - 1 ); if( M.n > P521_WIDTH + 1 ) M.n = P521_WIDTH + 1; M.p = Mp; memcpy( Mp, N->p + P521_WIDTH - 1, M.n * sizeof( t_uint ) ); MPI_CHK( mpi_shift_r( &M, 521 % ( 8 * sizeof( t_uint ) ) ) ); /* N = A0 */ N->p[P521_WIDTH - 1] &= P521_MASK; for( i = P521_WIDTH; i < N->n; i++ ) N->p[i] = 0; /* N = A0 + A1 */ MPI_CHK( mpi_add_abs( N, N, &M ) ); cleanup: return( ret ); } #undef P521_WIDTH #undef P521_MASK #endif /* POLARSSL_ECP_DP_SECP521R1_ENABLED */ #endif /* POLARSSL_ECP_NIST_OPTIM */ #if defined(POLARSSL_SELF_TEST) /* * Checkup routine */ int ecp_self_test( int verbose ) { int ret; size_t i; ecp_group grp; ecp_point R, P; mpi m; unsigned long add_c_prev, dbl_c_prev; /* exponents especially adapted for secp192r1 */ const char *exponents[] = { "000000000000000000000000000000000000000000000000", /* zero */ "000000000000000000000000000000000000000000000001", /* one */ "FFFFFFFFFFFFFFFFFFFFFFFF99DEF836146BC9B1B4D22831", /* N */ "5EA6F389A38B8BC81E767753B15AA5569E1782E30ABE7D25", /* random */ "400000000000000000000000000000000000000000000000", "7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF", "555555555555555555555555555555555555555555555555", }; ecp_group_init( &grp ); ecp_point_init( &R ); ecp_point_init( &P ); mpi_init( &m ); /* Use secp192r1 if available, or any available curve */ #if defined(POLARSSL_ECP_DP_SECP192R1_ENABLED) MPI_CHK( ecp_use_known_dp( &grp, POLARSSL_ECP_DP_SECP192R1 ) ); #else MPI_CHK( ecp_use_known_dp( &grp, ecp_curve_list()->grp_id ) ); #endif if( verbose != 0 ) printf( " ECP test #1 (constant op_count, base point G): " ); /* Do a dummy multiplication first to trigger precomputation */ MPI_CHK( mpi_lset( &m, 2 ) ); MPI_CHK( ecp_mul( &grp, &P, &m, &grp.G, NULL, NULL ) ); add_count = 0; dbl_count = 0; MPI_CHK( mpi_read_string( &m, 16, exponents[0] ) ); MPI_CHK( ecp_mul( &grp, &R, &m, &grp.G, NULL, NULL ) ); for( i = 1; i < sizeof( exponents ) / sizeof( exponents[0] ); i++ ) { add_c_prev = add_count; dbl_c_prev = dbl_count; add_count = 0; dbl_count = 0; MPI_CHK( mpi_read_string( &m, 16, exponents[i] ) ); MPI_CHK( ecp_mul( &grp, &R, &m, &grp.G, NULL, NULL ) ); if( add_count != add_c_prev || dbl_count != dbl_c_prev ) { if( verbose != 0 ) printf( "failed (%zu)\n", i ); ret = 1; goto cleanup; } } if( verbose != 0 ) printf( "passed\n" ); if( verbose != 0 ) printf( " ECP test #2 (constant op_count, other point): " ); /* We computed P = 2G last time, use it */ add_count = 0; dbl_count = 0; MPI_CHK( mpi_read_string( &m, 16, exponents[0] ) ); MPI_CHK( ecp_mul( &grp, &R, &m, &P, NULL, NULL ) ); for( i = 1; i < sizeof( exponents ) / sizeof( exponents[0] ); i++ ) { add_c_prev = add_count; dbl_c_prev = dbl_count; add_count = 0; dbl_count = 0; MPI_CHK( mpi_read_string( &m, 16, exponents[i] ) ); MPI_CHK( ecp_mul( &grp, &R, &m, &P, NULL, NULL ) ); if( add_count != add_c_prev || dbl_count != dbl_c_prev ) { if( verbose != 0 ) printf( "failed (%zu)\n", i ); ret = 1; goto cleanup; } } if( verbose != 0 ) printf( "passed\n" ); cleanup: if( ret < 0 && verbose != 0 ) printf( "Unexpected error, return code = %08X\n", ret ); ecp_group_free( &grp ); ecp_point_free( &R ); ecp_point_free( &P ); mpi_free( &m ); if( verbose != 0 ) printf( "\n" ); return( ret ); } #endif #endif