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https://github.com/logos-storage/constantine.git
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c97036d1df
* feat: MapToScalarField added for Banderwagon points * fix: syntax + NRVO * fix: comments added for function & spec files linked * feat: batchAffine + batchInversion * feat: batchMapToScalarField + tests * fix: comments and formatting * fix: static to openArray changed --------- Co-authored-by: Mamy Ratsimbazafy <mamy_github@numforge.co>
94 lines
3.2 KiB
Nim
94 lines
3.2 KiB
Nim
# 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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## ############################################################
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##
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## Verkle Trie primitives for Ethereum
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##
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## ############################################################
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import
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./math/config/[type_ff, curves],
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./math/arithmetic,
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./math/elliptic/[
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ec_twistededwards_projective,
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ec_twistededwards_batch_ops
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],
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./math/io/[io_bigints, io_fields],
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./curves_primitives
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func mapToBaseField*(dst: var Fp[Banderwagon],p: ECP_TwEdwards_Prj[Fp[Banderwagon]]) =
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## The mapping chosen for the Banderwagon Curve is x/y
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##
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## This function takes a Banderwagon element & then
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## computes the x/y value and returns as an Fp element
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##
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## Spec : https://hackmd.io/@6iQDuIePQjyYBqDChYw_jg/BJBNcv9fq#Map-To-Field
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var invY: Fp[Banderwagon]
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invY.inv(p.y) # invY = 1/Y
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dst.prod(p.x, invY) # dst = (X) * (1/Y)
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func mapToScalarField*(res: var Fr[Banderwagon], p: ECP_TwEdwards_Prj[Fp[Banderwagon]]): bool {.discardable.} =
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## This function takes the x/y value from the above function as Fp element
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## and convert that to bytes in Big Endian,
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## and then load that to a Fr element
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##
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## Spec : https://hackmd.io/wliPP_RMT4emsucVuCqfHA?view#MapToFieldElement
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var baseField: Fp[Banderwagon]
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var baseFieldBytes: array[32, byte]
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baseField.mapToBaseField(p) # compute the defined mapping
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let check1 = baseFieldBytes.marshalBE(baseField) # Fp -> bytes
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let check2 = res.unmarshalBE(baseFieldBytes) # bytes -> Fr
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return check1 and check2
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## ############################################################
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##
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## Batch Operations
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##
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## ############################################################
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func batchMapToScalarField*(
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res: var openArray[Fr[Banderwagon]],
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points: openArray[ECP_TwEdwards_Prj[Fp[Banderwagon]]]): bool {.discardable.} =
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## This function performs the `mapToScalarField` operation
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## on a batch of points
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##
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## The batch inversion used in this using
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## the montogomenry trick, makes is faster than
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## just iterating of over the array of points and
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## converting the curve points to field elements
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##
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## Spec : https://hackmd.io/wliPP_RMT4emsucVuCqfHA?view#MapToFieldElement
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var check: bool = true
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check = check and (res.len == points.len)
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let N = res.len
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var ys = allocStackArray(Fp[Banderwagon], N)
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var ys_inv = allocStackArray(Fp[Banderwagon], N)
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for i in 0 ..< N:
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ys[i] = points[i].y
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ys_inv.batchInvert(ys, N)
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for i in 0 ..< N:
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var mappedElement: Fp[Banderwagon]
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var bytes: array[32, byte]
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mappedElement.prod(points[i].x, ys_inv[i])
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check = bytes.marshalBE(mappedElement)
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check = check and res[i].unmarshalBE(bytes)
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return check |