mirror of https://gogs.blitter.com/RLabs/xs
33 lines
807 B
Go
33 lines
807 B
Go
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// poly.go - NewHope reductions.
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//
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// To the extent possible under law, Yawning Angel has waived all copyright
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// and related or neighboring rights to newhope, using the Creative
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// Commons "CC0" public domain dedication. See LICENSE or
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// <http://creativecommons.org/publicdomain/zero/1.0/> for full details.
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package newhope
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// Incomplete-reduction routines; for details on allowed input ranges
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// and produced output ranges, see the description in the paper:
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// https://cryptojedi.org/papers/#newhope
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const (
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qinv = 12287 // -inverse_mod(p,2^18)
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rlog = 18
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)
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func montgomeryReduce(a uint32) uint16 {
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u := a * qinv
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u &= ((1 << rlog) - 1)
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u *= paramQ
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a = (a + u) >> 18
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return uint16(a)
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}
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func barrettReduce(a uint16) uint16 {
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u := (uint32(a) * 5) >> 16
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u *= paramQ
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a -= uint16(u)
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return a
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}
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