I am using 3-DES to encrypt some data in Java. I decided to run some tests and plot some graphics to decide how to optimally pack data for its encryption (see how encryption/decryption time behave depending on the length of the plain text), so I measured the time to encrypt one thousand Strings of incremental size (first one of length 1, second one of length 2, etc.) and then did the same the other way around (decrypt the first results).
I find that the decryption time increases with the size of the resulting plain text, although the time/character decreases as a rule. However, for encryption all the tests take approximately the same amount of time (it takes as long to encrypt a 2-character String than a 1000-character String, ~0.003 ms).
Is this something inherent to 3-DES, to how Java implements it or maybe I measured the time wrongly?