>> plainText = char((64:123))

plainText =

@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{

>> rot13(plainText)

ans =

@NOPQRSTUVWXYZABCDEFGHIJKLM[\]^_`nopqrstuvwxyzabcdefghijklm{