What property of multiplication allows this technique? [video]
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In case you are genuinely asking, here's a link[0] to a post I wrote a while ago proving that it works, and generalising to powers of numbers (critical for cryptography) and powers of matrices.
I've submitted it as a separate post[1].
[0] http://www.solipsys.co.uk/new/RussianPeasantMultiplication.h...
There are various properties required of the things you're working on, and of the calculation you want to perform, but those properties aren't limited to multiplication. Having said that, not everything has the necessary properties, so as I say, I'm not sure what you're asking.