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The new method needs about 30 % less time for prime256k1 and is about twice as fast for other moduli. The base algorithm is the same. The code is also a bit smaller and doesn't need the 8 kb precomputed table. Important canges: 1. even/odd distinction so that we need to test only one of the numbers for being even. This also leads to less duplicated code. 2. Allow for shifting by 32 bits at a time in the even test. 3. Pack u,s and v,r into the same array, which saves a bit of stack memory. 4. Don't divide by two after subtraction; this simplifies code. 5. Abort as soon as u,v are equal, instead of subtracting them. 6. Use s instead of r after the loop; no negation needed. 7. New code that divides by 2^k fast without any precomputed values.
54 lines
1.7 KiB
C
54 lines
1.7 KiB
C
/**
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* Copyright (c) 2013-2014 Pavol Rusnak
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
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* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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#ifndef __OPTIONS_H__
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#define __OPTIONS_H__
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// use precomputed Curve Points (some scalar multiples of curve base point G)
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#ifndef USE_PRECOMPUTED_CP
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#define USE_PRECOMPUTED_CP 1
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#endif
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// use fast inverse method
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#ifndef USE_INVERSE_FAST
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#define USE_INVERSE_FAST 1
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#endif
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// support for printing bignum256 structures via printf
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#ifndef USE_BN_PRINT
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#define USE_BN_PRINT 0
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#endif
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// use deterministic signatures
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#ifndef USE_RFC6979
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#define USE_RFC6979 1
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#endif
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// implement BIP32 caching
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#ifndef USE_BIP32_CACHE
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#define USE_BIP32_CACHE 1
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#define BIP32_CACHE_SIZE 10
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#define BIP32_CACHE_MAXDEPTH 8
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#endif
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#endif
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