@bascule there are abelian groups (commutative) and non-abelian groups. Integers are an abelian group. So it depends on your other thing.
What I don't really understand about group theory: is multiplying a group element by an integer commutative?
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@brixen NaCl has a "standard group element" you multiply by to produce group elements -
@bascule it depends how you define the operation. Cf scalar matrix multiplication -
@brixen@nuclearsandwich not entirely sure, but here's the source code: https://github.com/jedisct1/libsodium/blob/master/src/libsodium/crypto_scalarmult/curve25519/ref/smult.c#L247 … -
@bascule if that code has docs somewhere I might be able to give you an answer. -
@nuclearsandwich hope you find RbNaCl to be well-documented. We've really been trying hard: https://github.com/cryptosphere/rbnacl/blob/master/lib/rbnacl/scalar.rb … -
@bascule I sadly don't have time to sit down and be good about it, but my intuition is that it probably doesn't commute. -
@nuclearsandwich not really an issue, just trying to double check my math on this: https://gist.github.com/tarcieri/4747652 … - 2 more replies
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@bascule Multiplication is an operation defined on a group. Multiplication of elements between two different groups is not well-defined. -
@danrabinowitz yeah, think I get that now. NaCl works by always multiplying first by a "standard group element" (i.e. constant group)
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@bascule It's not a group operation and so is not commutative. IIRC it's defined for the integer being on the left only. 3 * a := a + a + a. -
@yfeldblum yeah, so I think I've got this much right at least? https://github.com/cryptosphere/rbnacl/blob/master/lib/rbnacl/scalar.rb#L22 … (trying to wrap NaCl) -
@bascule Just in terms of the argument order, that's how it's typically represented IIRC.
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@bascule it depends on the group operation; for Z+, noThanks. Twitter will use this to make your timeline better. UndoUndo
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@bascule by multiplying do you mean performing the group operation i times on the element? a + a + a...Thanks. Twitter will use this to make your timeline better. UndoUndo
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