53 lines
1.9 KiB
Nim
53 lines
1.9 KiB
Nim
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# Constantine
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# Copyright (c) 2018-2019 Status Research & Development GmbH
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# Copyright (c) 2020-Present Mamy André-Ratsimbazafy
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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import
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# Internals
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../../constantine/config/[common, curves],
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../../constantine/arithmetic,
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../../constantine/elliptic/[ec_weierstrass_affine, ec_weierstrass_projective]
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# Support files for testing Elliptic Curve arithmetic
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# ------------------------------------------------------------------------------
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iterator unpack(scalarByte: byte): bool =
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yield bool((scalarByte and 0b10000000) shr 7)
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yield bool((scalarByte and 0b01000000) shr 6)
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yield bool((scalarByte and 0b00100000) shr 5)
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yield bool((scalarByte and 0b00010000) shr 4)
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yield bool((scalarByte and 0b00001000) shr 3)
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yield bool((scalarByte and 0b00000100) shr 2)
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yield bool((scalarByte and 0b00000010) shr 1)
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yield bool( scalarByte and 0b00000001)
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func unsafe_ECmul_double_add*(
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P: var ECP_SWei_Proj,
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scalar: openArray[byte],
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) =
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## **Unsafe** Elliptic Curve Scalar Multiplication
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##
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## P <- [k] P
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##
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## This uses the double-and-add algorithm to verify the constant-time production implementation
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## This is UNSAFE to use in production and only intended for testing purposes.
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##
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## This is highly VULNERABLE to timing attacks and power analysis attacks
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##
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## `scalar` is in canonical representation in BigEndian (octet string)
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var t0{.noInit.}, t1{.noInit.}: typeof(P)
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t0.setInf()
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t1.setInf()
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for scalarByte in scalar:
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for bit in unpack(scalarByte):
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t1.double(t0)
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if bit:
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t0.sum(t1, P)
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else:
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t0 = t1
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P = t0
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