If you, like me, are hesitant to put hard-coded user IDs, passwords, or whatever into your scripts, this bit of obfuscation may be of interest. The bad news is that the information is still in the script and decipherable by an astute intruder. The good news is that the typical computer user will find the ciphertext stored in your scripts to be utterly mysterious and incomprehensible.

Let me state clearly that this method is one of "security by obscurity." It is NOT going to provide genuine security, so use it at your own risk. I suppose one could slightly improve the pseudosecurity of this technique by writing the ciphertext to a text file, thus separating the information from the deciphering handlers.

As to the methodology employed, the code is my own spin on the ROT18 cipher with some extra twists thrown in. One twist is that spaces, periods, commas, and question marks are enciphered, along with letters and numbers (making it ROT20, I guess). Other characters, such as parentheses, will appear in the ciphertext as is. Another twist is the breaking up of the text into five chunks (or three, if the text is short) and shuffling the order of those chunks. If the text is really short, the order of the characters is simply reversed. Like ROT 18, this logic is self-inverting. That is, the same logic both enciphers plaintext and deciphers ciphertext.

Maybe you won't use it for passwords. You and a friend could generate coded messages to email to back and forth. Anyway, for whatever good it is, here is the code. Enjoy!

        set theText to "Quick Brown Fox, 73, Jumps(?) Over Lazy Dog 129."
        set cipherText to applyCodec(theText)
        set plaintextAgain to applyCodec(cipherText)
        return {cipherText, plaintextAgain}

        on applyCodec(theText) -- mutant ROT20 retains case of plaintext
                set lowerCharSet to "abcdefghijklmnopqrstuvwxyz.,? 0123456789"
                set lowerCipherSet to "uvwxyz.,? 0123456789abcdefghijklmnopqrst"
                set upperCharSet to "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                set upperCipherSet to "NOPQRSTUVWXYZABCDEFGHIJKLM"
                set cipherText to {}
                repeat with i from 1 to (length of theText)
                        set thisChar to character i of theText
                        considering case
                                if thisChar is in lowerCharSet then
                                        set x to offset of thisChar in lowerCharSet
                                        set end of cipherText to character x of lowerCipherSet
                                else if thisChar is in upperCharSet then
                                        set x to offset of thisChar in upperCharSet
                                        set end of cipherText to character x of upperCipherSet
                                else
                                        set end of cipherText to thisChar
                                end if
                        end considering
                end repeat
                return shuffle(cipherText as text)
        end applyCodec

        on shuffle(theText)
                set len to count of theText
                if len < 3 then
                        set shuffledChars to reverse of characters of theText
                else
                        set usingFifths to len > 29
                        if usingFifths then
                                set x to 5
                                set {a, b, c, d, e} to splitIntoFifths(len)
                        else -- using thirds
                                set x to 3
                                set {a, b, c} to splitIntoThirds(len)
                        end if
                        set shuffledChars to {}
                        set end of shuffledChars to reverse of characters (a + 1) thru (a + b) of theText
                        set end of shuffledChars to reverse of characters 1 thru a of theText
                        set end of shuffledChars to reverse of characters ¬
                                (a + b + 1) thru (a + b + c) of theText
                        if usingFifths then
                                set end of shuffledChars to reverse of characters ¬
                                        (a + b + c + d + 1) thru (a + b + c + d + e) of theText
                                set end of shuffledChars to reverse of characters ¬
                                        (a + b + c + 1) thru (a + b + c + d) of theText
                        end if
                end if
                return shuffledChars as text
        end shuffle

        on splitIntoFifths(n)
                set a to round (n / 5) rounding up
                set b to round ((n - a) / 4)
                set c to round (n - a - b) / 3
                set d to round (n - a - b - c) / 2
                set e to round (n - a - b - c - d)
                return {a, b, c, d, e}
        end splitIntoFifths

        on splitIntoThirds(n)
                set a to round (n / 3) rounding up
                set b to round ((n - a) / 2)
                set c to round (n - a - b)
                return {a, b, c}
        end splitIntoThirds