Right - the way you verify that is by asking for 100 sealed Alice envelopes, and opening 99 of them at random. If the machine was trying to trick you, you have

Right - the way you verify that is by asking for 100 sealed Alice envelopes, and opening 99 of them at random. If the machine was trying to trick you, you have a strong chance of catching it. You still walk out with a sealed envelope, and the would-be vote-buyer can't be sure it isn't a Bob envelope. This Numberphile video explains the process a bit more: https://www.youtube.com/watch?v=BYRTvoZ3Rho https://www.youtube.com/watch?v=BYRTvoZ3Rho