Just noticed we’ve got two alike tags:
Multiple encryption means encrypting a message two or more times using either the same, or a different algorithm.
Double encryption is the process of encrypting a message multiple times, either using the same or a different algorithm.
Both practically describe the same.
As you’ll notice, double-encryption is merely used by this question. Meaning: we could also simply replace that double-encryption tag and let the tag fade out, but chances are that someone else will come along and use that tag again… so I guess making it a synonym of the multi-encryption tag could be the smarter move. What do you think?