Can someone explain how long the proof of work needs today and how long it may take in the future? I always think about if paying in a supermarket with IOTA will ever be possible. And right now I need a long time to log into the light wallet, than to do the proof of work and after that get confirmed by the tangle network. So I guess people behind me will be upset if I pay with IOTA.
Short answer it depends.
A little longer answer, the needed time for the proof of work depends on:
- the device that calculates the hash.
- the load of this device (with other stuff).
- the minWeightMagnitude (here you can read more about it).
Furthermore the IOTA Foundation is planing/working on a external CPU called Jinn. Jinn is a ternary CPU so more optimist for IOTA and should have a better energy efficient and do the hash calculation faster.
Keep in mind that JINN is currently under NDA and doesn't release any information about its development. Some more Information can be found here.
The average duration of the pow is determined by the minWeightMagnitude (i.e the difficulty of the puzzle to solve) and the computing power of the device.
On Bitcoin, the difficulty of the pow is adjusted is such a way that there is a new block every 10 minutes (on average). (basically it is driven by the total computing power of the network)
On the Tangle, the difficulty of the pow (minWeightMagnitude) should be adjusted in such a way that "problematic spam" became so costly that it is abandoned (or at least don't arm the tangle significantly). Basically it is driven by "adoption rate" :
To simplify, the tangle have (at least) 2 ways to protect against "problematic spam" : the minWeightMagnitude (i.e. the computing power required to attach to the tangle) and the mass adoption (a tangle with many valid transactions is more difficult to arm)
If we imagine that IOTA became a money that can be used in the supermarket, it means "huge adoption", it means "huge amount of valid transaction", it means that spammers need to produce more and more invalid transactions to significantly arm the network. It means that the minWeightMagnitude can be reduced.
Regarding usage in the supermarket, remember that the first target of IOTA is micropayment in the machine to machine economy.