My friend wants to buy a phone from soneone on craigs list and they said they have it on 6.0.1, but saved the blobs and would give them to him when he goes to buy it. He would be able to downgrade even if the other guy got the blobs right?
You can verify that with Tinyumbrella or by using the latest redsnow.
He can give him a cd with someone elses blobs or no blobs are all when they meet for the exchange.
Only way to verfiy if he really cares about jailbreaking it untethered then he has to use Tinyumbrella or Redsnow.
The existence of SHSH can be verified before the sale.
Have the seller provide the ECID #, then use Redsn0w to verify if he has actually saved the SHSH.
And if they are in Cydia, they can always be retrieved from there, there is no need to physically exchange them.