If an adversary holds thousands of encrypted files that were encrypted with the same cipher, can he determine which cipher method had been used on the files? Assume that the adversary has no prior knowledge about the encryption environment.
Details: Let's say I have a encryption program that allows me to select 1 out of 5 well established and well implemented encryption algorithms. I use that program to encrypt thousands of file, using always the same block cipher, while following proper cryptographic procedures (e.g. use different passwords every n files encrypted). The files are stored off-site, and an adversary gets a hold of the files. I wonder if by selecting a less common algorithm, e.g. Serpent, I would increase the workload of the adversary by factor of 5, or encryption algorithms do leak some information, some recurring properties, that will help the adversary to identify the encryption method I had used?