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math/big: modInverse doesn't require a prime modulus #8875

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randall77 opened this issue Oct 6, 2014 · 3 comments
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math/big: modInverse doesn't require a prime modulus #8875

randall77 opened this issue Oct 6, 2014 · 3 comments
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@randall77
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The spec of math/big.modInverse requires the modulus to be prime.  But the inverse is
well defined as long as the number being inverted and the modulus are relatively prime. 
Perhaps more importantly, the current code seems to work for all of those cases.

Should we relax the spec to include these cases?
Any reason why the current code wouldn't always work with this relaxation?
@agl
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agl commented Oct 6, 2014

Comment 1:

There's no problem with relaxing that, but the prime modulus case was the only one that
I cared about and tested and thus the only one that I wanted to commit to.

@gopherbot
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Comment 2:

CL https://golang.org/cl/155010043 mentions this issue.

@randall77
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Comment 3:

This issue was closed by revision 96d1e4a.

Status changed to Fixed.

@golang golang locked and limited conversation to collaborators Jun 25, 2016
wheatman pushed a commit to wheatman/go-akaros that referenced this issue Jun 25, 2018
@randall77 @wheatman
math/big: Allow non-prime modulus for ModInverse
5499851 
The inverse is defined whenever the element and the
modulus are relatively prime.  The code already handles
this situation, but the spec does not.

Test that it does indeed work.

Fixes golang#8875

LGTM=agl
R=agl
CC=golang-codereviews
https://golang.org/cl/155010043
wheatman pushed a commit to wheatman/go-akaros that referenced this issue Jun 26, 2018
@randall77 @wheatman
math/big: Allow non-prime modulus for ModInverse
4fc1453 
The inverse is defined whenever the element and the
modulus are relatively prime.  The code already handles
this situation, but the spec does not.

Test that it does indeed work.

Fixes golang#8875

LGTM=agl
R=agl
CC=golang-codereviews
https://golang.org/cl/155010043
wheatman pushed a commit to wheatman/go-akaros that referenced this issue Jul 9, 2018
@randall77 @wheatman
math/big: Allow non-prime modulus for ModInverse
8503cc6 
The inverse is defined whenever the element and the
modulus are relatively prime.  The code already handles
this situation, but the spec does not.

Test that it does indeed work.

Fixes golang#8875

LGTM=agl
R=agl
CC=golang-codereviews
https://golang.org/cl/155010043
wheatman pushed a commit to wheatman/go-akaros that referenced this issue Jul 30, 2018
@randall77 @wheatman
math/big: Allow non-prime modulus for ModInverse
1ff3bc4 
The inverse is defined whenever the element and the
modulus are relatively prime.  The code already handles
this situation, but the spec does not.

Test that it does indeed work.

Fixes golang#8875

LGTM=agl
R=agl
CC=golang-codereviews
https://golang.org/cl/155010043
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@agl @randall77 @gopherbot