RosettaCodeData/Task/ADFGVX-cipher/FutureBasic/adfgvx-cipher.basic

/*
ADFGVX cipher
https://rosettacode.org/wiki/ADFGVX_cipher

Requires file, unixdict.txt to be on the desktop
https://github.com/quinnj/Rosetta-Julia/blob/master/unixdict.txt

*/

begin globals

  str255 ADFGVX
  ADFGVX  = "ADFGVX"
  str255 ALPHABET
  ALPHABET  = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

end globals

local fn InitialisePolybiusSquare As str255
  short i, j

  str255 letters(36)
  For i = 0 To 35
    letters(i) = Mid$(ALPHABET, i + 1, 1)
  Next

  For i = 0 To 35
    j = Int(rnd (36))
    Swap letters(i), letters(j)
  Next

  short row, column
  str255 result
  result = ""
  For row = 0 To 5
    For column = 0 To 5
      result = result + letters(6 * row + column)
    Next
  Next

End fn = result

local fn CreateKey(size As short) As str255
  If size < 7 Or size > 12
    Print "Key should contain between 7 and 12 letters, both inclusive."
    Exit fn
  End If

  short i, j
  str255 TheWord, candidates(1000)
  short ff = 1 // file number

  short CandidatesCounter = 1

  CFUrlRef ParentDirectory = fn FileManagerURLForDirectory( NSDesktopDirectory, NSUserDomainMask )
  CFUrlRef UnixDictURL = fn URLByAppendingPathComponent( ParentDirectory, @"unixdict.txt" )


  Open "I",ff, UnixDictURL
  While Eof(ff) = 0
    Line Input #ff, TheWord

    str255 uniqueWord
    uniqueWord = ""
    For i = 1 To Len$(TheWord)
      If Instr$(1,uniqueWord, Mid$(TheWord, i, 1)) = 0
        uniqueWord = uniqueWord +  Mid$(TheWord, i, 1)
      End If
    Next

    If Len$(TheWord) = size && Len$(TheWord) = Len$(uniqueWord)
      TheWord = Ucase$(TheWord)

      bool isAlphanum = _true
      For i = 1 To Len$(TheWord)
        If (Mid$(TheWord, i, 1) < "A" && Mid$(TheWord, i, 1) <= "Z") && (Mid$(TheWord, i, 1) < "0" && Mid$(TheWord, i, 1) <= "9")
          isAlphanum = _false
          Exit For
        End If
      Next


      If isAlphanum
        //Redim Preserve candidates(Ubound(candidates) + 1)
        CandidatesCounter ++
        candidates(CandidatesCounter) = TheWord
      End If
    End If
  Wend
  Close #ff



  For i = 0 To CandidatesCounter
    j = Int(Rnd (CandidatesCounter + 1))
    Swap candidates(i), candidates(j)
  Next

End fn = candidates(0)

local fn Encrypt(plainText As str255, polybius As str255, key As str255) As str255
  short i, j, row, column
  str255 code, ch, encrypted

  code = ""
  For i = 1 To Len$(plainText)
    ch = Mid$(plainText, i, 1)
    For row = 0 To 5
      For column = 0 To 5
        If Mid$(polybius, row * 6 + column + 1, 1) = ch
          code = code +  Mid$(ADFGVX, row + 1, 1)
          code = code +  Mid$(ADFGVX, column + 1, 1)
        End If
      Next
    Next
  Next

  encrypted = ""
  For i = 1 To Len$(key)
    ch = Mid$(key, i, 1)
    For j = Instr$(1,key, ch) - 1 To Len$(code) - 1 Step Len$(key)
      encrypted = encrypted +  Mid$(code, j + 1, 1)
    Next
    encrypted = encrypted +  " "
  Next


End fn = encrypted

local fn Decrypt(encryptedText As str255, polybius As str255, key As str255) As str255
  short i, j, row, column, spaceCount, codeSize
  str255 result, stream, TheWord, code, plainText
  str255 blocks(200)
  short BlocksCounter = 1
  result = ""
  i = 1
  While i <= Len$(encryptedText)
    If Mid$(encryptedText, i, 1) = " "
      i += 1
    Else
      result += Mid$(encryptedText, i, 1)
      i += 1
    End If
  Wend
  spaceCount = Len$(encryptedText) - Len$(result)
  codeSize = Len$(encryptedText) - spaceCount


  stream = encryptedText
  While Len$(stream) > 0
    TheWord = Left$(stream, Instr$(1,stream, " ") - 1)
    //Redim Preserve blocks(Ubound(blocks) + 1)
    BlocksCounter ++
    blocks(BlocksCounter) = TheWord
    stream = Mid$(stream, Instr$(1,stream, " ") + 1)
  Wend

  code = ""
  For i = 0 To codeSize - 1
    BlocksCounter ++
    For j = 0 To BlocksCounter
      If Len$(code) < codeSize Then code = code + Mid$(blocks(j), i + 1, 1)
    Next
  Next

  plainText = ""
  For i = 1 To codeSize - 1 Step 2
    row = Instr$(1,ADFGVX, Mid$(code, i, 1)) - 1
    column = Instr$(1,ADFGVX, Mid$(code, i + 1, 1)) - 1
    plainText = plainText +  Mid$(polybius, row * 6 + column + 1, 1)
  Next


End fn = plainText

str255 polybius
polybius = fn InitialisePolybiusSquare
Print "The 6 x 6 Polybius square:"
Print " | A D F G V X"
Print "--------------"
short row
For row = 0 To 5
  Print Mid$(ADFGVX, row + 1, 1); "|";
  short column
  For column  = 0 To 5
    Print " "; Mid$(polybius, row * 6 + column + 1, 1);
  Next
  Print
Next

str255 key
key = fn CreateKey(9)
print
Print "The key is "; key
str255 plainText
plainText = "ATTACKAT1200AM"// 20241105
print
Print "Plain text: "; plainText
str255 encryptedText
encryptedText = fn Encrypt(plainText, polybius, key)
print
Print "Encrypted: "; encryptedText
str255 decryptedText
decryptedText = fn Decrypt(encryptedText, polybius, key)
print
Print "Decrypted: "; decryptedText

handleevents