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simplify bncurve getPoint

This commit is contained in:
jangko 2020-12-02 16:17:52 +07:00
parent fab894f5ad
commit 397119468a
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GPG Key ID: 31702AE10541E6B9
1 changed files with 13 additions and 19 deletions
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32
nimbus/vm/precompiles.nim
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@ -62,6 +62,17 @@ proc getSignature(computation: Computation): (array[32, byte], Signature) =
else:
raise newException(ValidationError, "Invalid V in getSignature")
proc simpleDecode*(dst: var FQ2, src: openarray[byte]): bool {.noinit.} =
# bypassing FQ2.fromBytes
# because we want to check `value > modulus`
result = false
if dst.c1.fromBytes(src.toOpenArray(0, 31)) and
dst.c0.fromBytes(src.toOpenArray(32, 63)):
result = true
template simpleDecode*(dst: var FQ, src: openarray[byte]): bool =
fromBytes(dst, src)
proc getPoint[T: G1|G2](t: typedesc[T], data: openarray[byte]): Point[T] =
when T is G1:
const nextOffset = 32
@ -69,28 +80,11 @@ proc getPoint[T: G1|G2](t: typedesc[T], data: openarray[byte]): Point[T] =
else:
const nextOffset = 64
var px, py: FQ2
if not px.fromBytes2(data.toOpenArray(0, nextOffset - 1)):
if not px.simpleDecode(data.toOpenArray(0, nextOffset - 1)):
raise newException(ValidationError, "Could not get point value")
if not py.fromBytes2(data.toOpenArray(nextOffset, nextOffset * 2 - 1)):
if not py.simpleDecode(data.toOpenArray(nextOffset, nextOffset * 2 - 1)):
raise newException(ValidationError, "Could not get point value")
# "ecpairing_perturb_g2_by_field_modulus_again.json",
# "ecpairing_perturb_zeropoint_by_field_modulus.json",
# "ecpairing_perturb_g2_by_field_modulus.json",
# modulus comparion in FQ2.fromBytes produce different result
const
modulus = Uint256.fromHex("30644e72e131a029b85045b68181585d97816a916871ca8d3c208c16d87cfd47")
let a = Uint256.fromBytesBE(data.toOpenArray(0, 31), false)
let b = Uint256.fromBytesBE(data.toOpenArray(32, 63), false)
when T is G2:
let c = Uint256.fromBytesBE(data.toOpenArray(64, 95), false)
let d = Uint256.fromBytesBE(data.toOpenArray(96, 127), false)
if a >= modulus or b >= modulus or c >= modulus or d >= modulus:
raise newException(ValidationError, "value greater than field modulus")
else:
if a >= modulus or b >= modulus:
raise newException(ValidationError, "value greater than field modulus")
if px.isZero() and py.isZero():
result = T.zero()
else: