Let's have an encryption CHALLENGE!

[oracle]

Try this on for size. Remember you won't have access to the key, but you can access the file with the encrypted string in it.

Code:

'                       **  Encryption routine **

'                             By the oracle

' This is a function I made up a while ago when working with zack on a
' GUI login for QBasic. We never got around to finishing it...

' This program has a key, it is outputted to a file at the moment, but
' this could be changed in the future.

DECLARE SUB encrypt (encrypt$)

RANDOMIZE TIMER
CLS
PRINT "The oracle's encryption routine"
PRINT "This program will take a string that you input and encrypt it."
PRINT "The result is outputted to a file"
PRINT "F-keys etc will be trimmed from the string. Only valid characters, please!"
PRINT
INPUT "What is the string you want to encrypt? ", enc$

t# = TIMER
encrypt enc$
t# = TIMER - t#

PRINT "The string has been outputted to strng.txt."
PRINT "The encryption took "; t#; "seconds."
INPUT "Do you want to view the string? ", yn$
IF LCASE$(LEFT$(yn$, 1)) = "y" THEN
  OPEN "strng.txt" FOR INPUT AS #1
  INPUT #1, a$
  PRINT a$
  WHILE INKEY$ = "": WEND
  CLOSE #1
END IF
END

SUB encrypt (enc$)

' DIM stuff

DIM rndlen AS INTEGER, ikey AS INTEGER, i AS INTEGER, handle AS INTEGER, keyhandle AS INTEGER

' Make a random key

rndlen = INT(RND * 500)
FOR i = 1 TO rndlen
  key$ = key$ + CHR$(INT(RND * 95) + 32)
NEXT i

' Encrypt the inputted string based on the key.

key$ = "!"
FOR i = 1 TO LEN(enc$)
  handle = ASC(MID$(enc$, i, 1))  ' I'm unfamiliar with PEEK
  ikey = ikey + 1
  IF ikey > LEN(key$) THEN ikey = 1
  keyhandle = ASC(MID$(key$, ikey, 1))
  temp& = INT(handle * keyhandle + 9999)
  temp$ = LTRIM$(STR$(temp&))
  FOR inc = LEN(temp$) TO 7
    temp$ = "0" + temp$
  NEXT inc
  encryptedstring$ = encryptedstring$ + temp$
NEXT i


OPEN "strng.txt" FOR OUTPUT AS #1
PRINT #1, encryptedstring$
CLOSE
OPEN "key.txt" FOR OUTPUT AS #1
PRINT #1, key$
CLOSE

END SUB

Beat that!