220 lines
6.5 KiB
C
220 lines
6.5 KiB
C
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/***************************************************************************
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*
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Copyright 2013 CertiVox UK Ltd. *
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*
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This file is part of CertiVox MIRACL Crypto SDK. *
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*
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The CertiVox MIRACL Crypto SDK provides developers with an *
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extensive and efficient set of cryptographic functions. *
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For further information about its features and functionalities please *
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refer to http://www.certivox.com *
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*
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* The CertiVox MIRACL Crypto SDK is free software: you can *
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redistribute it and/or modify it under the terms of the *
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GNU Affero General Public License as published by the *
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Free Software Foundation, either version 3 of the License, *
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or (at your option) any later version. *
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*
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* The CertiVox MIRACL Crypto SDK is distributed in the hope *
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that it will be useful, but WITHOUT ANY WARRANTY; without even the *
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implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. *
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See the GNU Affero General Public License for more details. *
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*
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* You should have received a copy of the GNU Affero General Public *
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License along with CertiVox MIRACL Crypto SDK. *
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If not, see <http://www.gnu.org/licenses/>. *
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*
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You can be released from the requirements of the license by purchasing *
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a commercial license. Buying such a license is mandatory as soon as you *
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develop commercial activities involving the CertiVox MIRACL Crypto SDK *
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without disclosing the source code of your own applications, or shipping *
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the CertiVox MIRACL Crypto SDK with a closed source product. *
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*
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***************************************************************************/
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/*
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* Module to implement Comb method for fast
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* computation of g^x mod n, for fixed g and n, using precomputation.
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* This idea can be used to substantially speed up certain phases
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* of the Digital Signature Standard (DSS) for example.
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*
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* See "Handbook of Applied Cryptography", CRC Press, 2001
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*/
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#include <stdlib.h>
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#include "miracl.h"
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#ifndef MR_STATIC
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BOOL brick_init(_MIPD_ brick *b,big g,big n,int window,int nb)
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{ /* Uses Montgomery arithmetic internally *
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* g is the fixed base for exponentiation *
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* n is the fixed modulus *
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* nb is the maximum number of bits in the exponent */
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int i,j,k,t,bp,len,bptr,is;
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big *table;
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#ifdef MR_OS_THREADS
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miracl *mr_mip=get_mip();
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#endif
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if (nb<2 || window<1 || window>nb || mr_mip->ERNUM) return FALSE;
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t=MR_ROUNDUP(nb,window);
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if (t<2) return FALSE;
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MR_IN(109)
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#ifndef MR_ALWAYS_BINARY
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if (mr_mip->base != mr_mip->base2)
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{
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mr_berror(_MIPP_ MR_ERR_NOT_SUPPORTED);
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MR_OUT
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return FALSE;
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}
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#endif
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b->window=window;
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b->max=nb;
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table=(big *)mr_alloc(_MIPP_ (1<<window),sizeof(big));
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if (table==NULL)
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{
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mr_berror(_MIPP_ MR_ERR_OUT_OF_MEMORY);
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MR_OUT
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return FALSE;
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}
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b->n=mirvar(_MIPP_ 0);
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copy(n,b->n);
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prepare_monty(_MIPP_ n);
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nres(_MIPP_ g,mr_mip->w1);
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convert(_MIPP_ 1,mr_mip->w2);
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nres(_MIPP_ mr_mip->w2,mr_mip->w2);
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table[0]=mirvar(_MIPP_ 0);
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copy(mr_mip->w2,table[0]);
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table[1]=mirvar(_MIPP_ 0);
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copy(mr_mip->w1,table[1]);
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for (j=0;j<t;j++)
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nres_modmult(_MIPP_ mr_mip->w1,mr_mip->w1,mr_mip->w1);
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k=1;
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for (i=2;i<(1<<window);i++)
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{
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table[i]=mirvar(_MIPP_ 0);
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if (i==(1<<k))
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{
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k++;
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copy(mr_mip->w1,table[i]);
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for (j=0;j<t;j++)
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nres_modmult(_MIPP_ mr_mip->w1,mr_mip->w1,mr_mip->w1);
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continue;
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}
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bp=1;
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copy(mr_mip->w2,table[i]);
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for (j=0;j<k;j++)
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{
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if (i&bp)
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{
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is=1<<j;
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nres_modmult(_MIPP_ table[is],table[i],table[i]);
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}
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bp<<=1;
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}
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}
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/* create the table */
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len=n->len;
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bptr=0;
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b->table=(mr_small *)mr_alloc(_MIPP_ len*(1<<window),sizeof(mr_small));
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for (i=0;i<(1<<window);i++)
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{
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for (j=0;j<len;j++)
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{
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b->table[bptr++]=table[i]->w[j];
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}
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mirkill(table[i]);
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}
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mr_free(table);
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MR_OUT
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return TRUE;
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}
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void brick_end(brick *b)
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{
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mirkill(b->n);
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mr_free(b->table);
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}
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#else
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/* use precomputated table in ROM - see ebrick2.c for example of how to create such a table, and ecdh.c
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for an example of use */
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void brick_init(brick *b,const mr_small *table,big n,int window,int nb)
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{
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b->table=table;
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b->n=n;
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b->window=window;
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b->max=nb;
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}
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#endif
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void pow_brick(_MIPD_ brick *b,big e,big w)
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{
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int i,j,t,len,promptr,maxsize;
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#ifdef MR_OS_THREADS
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miracl *mr_mip=get_mip();
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#endif
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if (size(e)<0) mr_berror(_MIPP_ MR_ERR_NEG_POWER);
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t=MR_ROUNDUP(b->max,b->window);
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MR_IN(110)
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#ifndef MR_ALWAYS_BINARY
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if (mr_mip->base != mr_mip->base2)
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{
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mr_berror(_MIPP_ MR_ERR_NOT_SUPPORTED);
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MR_OUT
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return;
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}
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#endif
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if (logb2(_MIPP_ e) > b->max)
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{
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mr_berror(_MIPP_ MR_ERR_EXP_TOO_BIG);
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MR_OUT
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return;
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}
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prepare_monty(_MIPP_ b->n);
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j=recode(_MIPP_ e,t,b->window,t-1);
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len=b->n->len;
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maxsize=(1<<b->window)*len;
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promptr=j*len;
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init_big_from_rom(mr_mip->w1,len,b->table,maxsize,&promptr);
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for (i=t-2;i>=0;i--)
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{
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j=recode(_MIPP_ e,t,b->window,i);
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nres_modmult(_MIPP_ mr_mip->w1,mr_mip->w1,mr_mip->w1);
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if (j>0)
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{
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promptr=j*len;
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init_big_from_rom(mr_mip->w2,len,b->table,maxsize,&promptr);
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nres_modmult(_MIPP_ mr_mip->w1,mr_mip->w2,mr_mip->w1);
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}
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}
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redc(_MIPP_ mr_mip->w1,w);
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MR_OUT
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}
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