multiple DES cipher same plain

[atom]

Note that it depends if you know the PT already. In this case you can encrypt the PT and then compare against a list of CT, which minimal speed drop. However if you need to decrypt the CT and then compare with PT (in most of the cases if you know only parts of the PT), then the speed drops by the number of salts. For the first technique, having only 15 possible keys is an easy job and you will get full speed. Just make sure they all have the same PT (salt).