Data update

Task/Bifid-cipher/FreeBASIC/bifid-cipher.basic

@@ -0,0 +1,81 @@
+Dim Shared As String encrypted, decrypted
+
+Sub BifidEncode(Byref polybius As String, Byref mensaje As String)
+    Dim As String filas, columas
+    Dim As Integer c, i, j, k, longi
+
+    encrypted = Ucase(mensaje)
+    For i = 1 To Len(encrypted)
+        If Mid(encrypted, i, 1) = Chr(10) Then Mid(encrypted, i, 1) = Chr(9)
+    Next i
+
+
+    i = 0 : j = 0
+    While i < Len(encrypted)
+        c = Asc(Mid(encrypted, i + 1, 1))
+        i += 1
+        k = Instr(polybius, Chr(c)) - 1
+        If k >= 0 Then
+            filas &= Chr(k \ 5 + Asc("0"))
+            columas &= Chr(k Mod 5 + Asc("0"))
+            j += 1
+        End If
+    Wend
+
+    longi = j
+    filas &= columas
+
+    encrypted = ""
+    For i = 0 To longi - 1
+        k = (Asc(Mid(filas, i * 2 + 1, 1)) - Asc("0")) * 5 + (Asc(Mid(filas, i * 2 + 2, 1)) - Asc("0"))
+        encrypted &= Mid(polybius, k + 1, 1)
+    Next i
+End Sub
+
+Sub BifidDecode(Byref polybius As String, Byref mensaje As String)
+    Dim As String filas, columas
+    Dim As Integer c, k, i, j, longi
+
+    i = 0 : j = 0
+    While i < Len(mensaje)
+        c = Asc(Mid(mensaje, i + 1, 1))
+        i += 1
+        k = Instr(polybius, Chr(c)) - 1
+        filas &= Chr(k \ 5 + Asc("0"))
+        filas &= Chr(k Mod 5 + Asc("0"))
+        j += 2
+    Wend
+
+    longi = i
+    columas = Right(filas, longi)
+    filas = Left(filas, longi)
+
+    decrypted = ""
+    For i = 0 To longi - 1
+        k = (Asc(Mid(filas, i + 1, 1)) - Asc("0")) * 5 + (Asc(Mid(columas, i + 1, 1)) - Asc("0"))
+        decrypted &= Mid(polybius, k + 1, 1)
+    Next i
+End Sub
+
+Dim As String polys(3), msgs(3)
+
+polys(0) = "ABCDEFGHIKLMNOPQRSTUVWXYZ"
+polys(1) = "BGWKZQPNDSIOAXEFCLUMTHYVR"
+polys(2) = "BGWKZQPNDSIOAXEFCLUMTHYVR"
+polys(3) = "PLAYFIREXMBCDGHKNOQSTUVWZ"
+
+msgs(0) = "ATTACKATDAWN"
+msgs(1) = "FLEEATONCE"
+msgs(2) = "ATTACKATDAWN"
+msgs(3) = "The invasion will start on the first of January"
+
+For i As Integer = 0 To Ubound(msgs)
+    BifidEncode(polys(i), msgs(i))
+    BifidDecode(polys(i), encrypted)
+    Print "Mensaje   : "; msgs(i)
+    Print "Encrypted : "; encrypted
+    Print "Decrypted : "; decrypted
+    If i < Ubound(msgs) Then Print
+Next i
+
+Sleep