It looks as too generic question, depends on what kind encyrpted message and what is character
Let’s say, just as a guess, if you encrypted message is a string and every “character” represented by Koitlin Char, than to split it you can just do
val chars: List<Char> = “encrypted message”..toList()
If character is some more complex structure (like multiple bytes/Chars) you need too write own parser for it