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Super simple encryption needed

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  • #1

    Super simple encryption needed

    Hi!

    I'm in need of a very easy to implement encryption routine which
    does not have to be advanced at all. I'm sure that there are
    advanced routines out there which can do a much nicer job but I
    really only need about this; Put encrypted in a string and call a
    subroutine which converts/interprets it and place the decrypted
    data in the same or in another string which I can print. The
    reason is that I want to prevent that a user edits my file with
    a hex editor or similar and replace characters.

    Anybody who has such a simple thing around?

    Many thanks in advance!

    ------------------
    Tags: pbcrypto
  • #2
    You can call this routine to encrypt data .. then call the same
    routine to decrypt it. Change the key however you like.

    Code:
      Dim EKey?(1:8)
  EKey?(1) = Asc("E")
  EKey?(2) = Asc("N")
  EKey?(3) = Asc("C")
  EKey?(4) = Asc("R")
  EKey?(5) = Asc("Y")
  EKey?(6) = Asc("P")
  EKey?(7) = Asc("T")
  EKey?(8) = Asc("X")

  eptr% = 0
  x = Len(Stuffin$)
  z$ = stuffin$  'output string
  inseg??? = STRSEG(stuffin$)
  inptr??? = StrPtr(stuffin$)
  outseg??? = STRSEG(z$)
  outptr??? = StrPtr(z$)
  For I = 1 To x
    Incr eptr%
    If eptr% > 8 Then
      eptr% = 1
    End If
    DEF SEG = inseg???
    tin? = Peek(inptr???)
    DEF SEG
    cout? = tin? Xor eKey?(eptr%)
    DEF SEG = outseg???
    Poke outptr???,cout?
    DEF SEG
    Incr inptr???
    Incr outptr???
  Next
  EncryptData$ = z$
 End Function
    No doubt someone can help make it faster ...

    Mike

    ------------------

    Comment

    • #3
      Mike! Great, thanks! But I can't compile it, and I assume it is
      missing the function statement... can you possibly fill in the
      missing data? Also, how would I call it?

      Again, thanks!

      Originally posted by Mike Burns:
      You can call this routine to encrypt data .. then call the same
      routine to decrypt it. Change the key however you like.

      Code:
        Dim EKey?(1:8)
  EKey?(1) = Asc("E")
  EKey?(2) = Asc("N")
  EKey?(3) = Asc("C")
  EKey?(4) = Asc("R")
  EKey?(5) = Asc("Y")
  EKey?(6) = Asc("P")
  EKey?(7) = Asc("T")
  EKey?(8) = Asc("X")

  eptr% = 0
  x = Len(Stuffin$)
  z$ = stuffin$  'output string
  inseg??? = STRSEG(stuffin$)
  inptr??? = StrPtr(stuffin$)
  outseg??? = STRSEG(z$)
  outptr??? = StrPtr(z$)
  For I = 1 To x
    Incr eptr%
    If eptr% > 8 Then
      eptr% = 1
    End If
    DEF SEG = inseg???
    tin? = Peek(inptr???)
    DEF SEG
    cout? = tin? Xor eKey?(eptr%)
    DEF SEG = outseg???
    Poke outptr???,cout?
    DEF SEG
    Incr inptr???
    Incr outptr???
  Next
  EncryptData$ = z$
 End Function
      No doubt someone can help make it faster ...

      Mike


      ------------------

      Comment

      • #4
        Sorry ... I missed a line on cut and paste

        Function EncryptData$(Stuffin$)

        that is the line I missed

        Mike


        ------------------

        Comment

        • #5
          I managed to compile it by making it a subroutine and skipping
          END FUNCTION statement. It really works good (good encryption),
          but can I limit the type of coded characters it uses in some
          simple way (a range)? As the code is now, if I encrypt the text
          'PowerBASIC' the first character 'P' will be converted to the
          paragraph character which makes it impossible(?) to insert into
          the PowerBASIC editor since it it contains illegal characters.

          If the encrypted data would always be A-Z & 0-9 then it should
          work 100% I guess... or?

          *Thanks* again and sorry for bothering you again!

          ------------------

          Comment

          • #6
            Aliases are not allowed in these forums, BL BL. Please re-register using
            your real name.

            ------------------
            Tom Hanlin
            PowerBASIC Staff

            Comment

            • #7
              bl,

              i use that routine when in a write to a disk and read from
              a disk routine ..

              i have never used it to change a string and display it. in order to do that,
              you would need to check what the xor function would produce for
              each character. i wouldn't think that would be feasible. for a better
              way to encrypt in memory or to control the encryption results
              look at the thread
              http://www.powerbasic.com/support/pb...ead.php?t=3267

              semen has posted a nice translate routine .. using that routine and
              two tables, you could change the printable characters to other
              printable characters and back again. then you would have control
              over what each character is encrypted as ..

              mike


              ------------------

              Comment

              • #8
                If all you want is to simply encrypt is printable text along
                with some control characters, you may want to try this:

                Set up a For-Next loop, take the ASCII characters of the text
                and add 128 to convert them to the extended character set. For
                the odd numbered characters, subtract 1 and for the even
                numbered characters, add 1 (or visa-vis). Take into account the
                possibility of a "wrap-around". To decrypt, simply reverse
                the procedure.

                This would be about as simple as you can get. It won't stand up
                to any kind of serious hacking but it should keep casual
                browsers out.


                ------------------
                There are no atheists in a fox hole or the morning of a math test.
                If my flag offends you, I'll help you pack.

                Comment

                • #9
                  You could use the HEX function.
                  EG like this for encrypting:

                  Code:
                  string1$ = "abc"
string2$ = ""
for i = 1 to len(string1$)
  string2$ = string2$ + mid$(string1$, i, 1
next i

                  Comment

                  • #10
                    Just another one of many ideas - try

                    Code:
                    ' --------------------------------------------------
'FUNCTION EnCoded$ (aString$)
'    Returns encoded aString$.  Before using, initialize the global
'    variable, Rand.Byte?, with a key value (eg. Rand.Byte? = &B01001011).
'
FUNCTION EnCoded$ (aString$)
  LOCAL i%, answer$
'
  answer$ = SPACE$(LEN(aString$))
  FOR i% = 1 TO LEN(aString$)
    MID$(answer$, i%, 1) = CHR$(ASCII(MID$(aString$, i%, 1)) + 1 + RandByte? \ 2)
  NEXT
  EnCoded$ = answer$
END FUNCTION
'
' --------------------------------------------------
'FUNCTION DeCoded$ (aString$)
'    Returns decoded aString$.  Before using, initialize the global
'    variable, Rand.Byte?, with the key used at the time of encoding
'    (eg. Rand.Byte? = &B01001011).
'
FUNCTION DeCoded$ (aString$)
  LOCAL i%, answer$
'
  answer$ = SPACE$(LEN(aString$))
  FOR i% = 1 TO LEN(aString$)
    MID$(answer$, i%, 1) = CHR$(ASCII(MID$(aString$, i%, 1)) - 1 - RandByte? \ 2)
  NEXT
  DeCoded$ = answer$
END FUNCTION
'
' -------------------------------------------------------------
'FUNCTION RandByte?
'    Returns next byte value in random sequence of values.  The routine
'    is seeded by setting the global, Rand.Byte?, to a value between 1
'    and 255.  The cycle length is 216.
'
FUNCTION RandByte?
  SHARED Rand.Byte?
'
  IF BIT(Rand.Byte?, 0) XOR BIT(Rand.Byte?, 3) THEN
    BIT SET Rand.Byte?, 0
  ELSE
    BIT RESET Rand.Byte?, 0
  END IF
  ROTATE RIGHT Rand.Byte?, 1
  RandByte? = Rand.Byte?
END FUNCTION
                    To test it, try

                    Code:
                    text$ = COMMAND$
'
Rand.Byte? = &B01001011
coded$ = EnCoded$ (text$)
'
PRINT coded$
'
Rand.Byte? = &B01001011
PRINT DeCoded$(coded$)
                    Keith

                    ------------------




                    [This message has been edited by Keith Waters (edited February 14, 2001).]

                    Comment

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