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math/big: typo in documentation for Int.Exp #38304

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hallazzang opened this issue Apr 8, 2020 · 6 comments
Closed

math/big: typo in documentation for Int.Exp #38304

hallazzang opened this issue Apr 8, 2020 · 6 comments
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Documentation FrozenDueToAge help wanted NeedsFix The path to resolution is known, but the work has not been done.
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@hallazzang
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go/src/math/big/int.go

Lines 467 to 473 in 97711bf

// Exp sets z = x**y mod |m| (i.e. the sign of m is ignored), and returns z.
// If m == nil or m == 0, z = x**y unless y <= 0 then z = 1. If m > 0, y < 0,
// and x and n are not relatively prime, z is unchanged and nil is returned.
//
// Modular exponentiation of inputs of a particular size is not a
// cryptographically constant-time operation.
func (z *Int) Exp(x, y, m *Int) *Int {

On line 469, it says ... x and n are not relatively prime, ... but there's no n in anywhere.
It should be m instead.
@randall77
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While someone is here, it says both m>0 and the sign of m is ignored. That first part should probably be m != 0.

@andybons andybons added help wanted NeedsFix The path to resolution is known, but the work has not been done. labels Apr 8, 2020
@andybons andybons added this to the Unplanned milestone Apr 8, 2020
@hallazzang
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@randall77 maybe just removing that (i.e. the sign of m is ignored) is fine enough?

@randall77
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I guess it all depends on what it actually does for m<0.

@abemotion abemotion mentioned this issue Apr 12, 2020
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@gopherbot
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Change https://golang.org/cl/227998 mentions this issue: math/big: fix typo in documentation for Int.Exp

@hallazzang
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I think leaving (i.e. the sign of m is ignored) and change m > 0 to m != 0 makes much sense.

hallazzang added a commit to hallazzang/go that referenced this issue Apr 12, 2020
@hallazzang
math/big: fix typo in documentation for Int.Exp
2399510 
Fixes golang#38304
@hallazzang hallazzang mentioned this issue Apr 12, 2020
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@gopherbot
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Change https://golang.org/cl/228000 mentions this issue: math/big: fix typo in documentation for Int.Exp

@golang golang locked and limited conversation to collaborators Apr 15, 2021
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@andybons @hallazzang @randall77 @gopherbot