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In crypto protocols that contains calculus on elliptic curves I can often see $\dfrac{m}{q}$$Q$ where $m$ stands for order of EC points group and $q$ is the order of corresponding subgroup of $m$. $Q \in q$.

What is the possible sense of this multiplication speaking mathematically?

It's possible that protocol example will be needed. Here it is:enter image description here

e-sushi
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im_infamous
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    It is often a requirement to make sure points are from the same subgroup of a prime order. This could be done by multiplying a point by the cofactor. – Vadym Fedyukovych Jan 07 '16 at 15:32
  • @VadymFedyukovych Ok, in this case, for what purpose this multiplier(cofactor) at steps of computing $K_a$ and $K_b$ is used? – im_infamous Jan 07 '16 at 20:22
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    Point $u_1$ (a group element) is received by B from A, so it is untrusted, in terms of being from the right subgroup. B is forcing this condition with a cofactor, I guess. – Vadym Fedyukovych Jan 08 '16 at 23:18
  • Related http://crypto.stackexchange.com/questions/18222/difference-between-ecdh-with-cofactor-key-and-ecdh-without-cofactor-key – dave_thompson_085 Apr 28 '16 at 08:43

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