Not sure if you are serious or not.. a-f,0-9 means it's hexadecimal characters, therefore say you wanted to guess a pk which is only 5 characters long it would already be 16x16x16x16x16 combinations, which sums up to 1048576.
If you think that's a lot.. then do you know how many combinations are there for a 64 hexadecimal characters long private key?
1.1579208921×10⁷⁷ if my math is correct, or 115792089210000000000000000000000000000000000000000000000000000000000000000000. That's probably more than the amount of grains of sand in this planet.
Imagine how long would it take to bruteforce that.
Also you are not talking about etherdelta specifically, those private keys can be used with any ethereum wallet. But trust me, if you ask that kind of question might be not a good idea for you to use etherdelta (no offense!).
Maybe hes already trying to make his own combinations as of now and hoping that he can able to access a wallet with have some decent balance on it.Basing on your calculations it is really accurate since if you do try to make combinations you would really took forever before you can find other wallet even changing a single character would already make a new wallet.Combinations would really be lots.Tell you frankly i have tried out that way wayback before which i do made some combinations but i did realize that its impossible.
Ahhaahahah.. maybe OP is still trying to manually enter combinations.
But as I said, even if one had to procedurally bruteforce their way in through a computer program, they would have a very hard time. Say you manage to do a trillion of trillions of trillions of trillions of trillions of trillions combinations.. you'd still have 115791989210000000000000000000000000000000000000000000000000000000000000000000 combinations to do.. 64 hexadecimal characters doesn't look threatening to the non-math-educated average Joe but is really no joke.
Having said this, if one day computers will have enough processing power to bruteforce that, then the entire blockchain concept as we know it today will need to be modified accordingly.
Perhaps with a 1024 hexadecimal characters private key? ;-)