[markus_v]

But couldn't you just take a photo of the ballot? Considering that not submitting the ballot after taking it is not allowed here.

[muthdra]

I think you have to reliably prove that it's your ballot and that it wasn't tampered with after the photo. Halter Voters would sometimes include a specific marking on the ballot that confirmed it was a succesfully bought vote so people could be personally rewarded accordingly.