Version 1 of Blowfish Tk Client

Updated 2005-07-12 17:23:54

snichols Below is some Tcl/Tk code for demonstrating how Tcl's blowfish encryption algorythm works. This TK app uses a plain text key field and plain text data field to create a encrypted blowfish data field. This app also allows you to save and load the data fields from file.

Tcl Blowfish Caveats I have found through testing:

- If the plain text data field is not divisible by 8 then extra characters are added to the decoded data field when it is decrypted.

- Decoding a plain text data field will actually encrypt it.

- Security is based on the plain text field key size. The bigger the key size the better the encryption.

- When saving/opening files the file translation needs to be binary.

        package require Tk
        package require BWidget
        package require blowfish

        # Create the window
        proc BlowfishTool {} {

                global data key mode

                set mode cbc

                trace variable file w LoadFile

                . configure -borderwidth 1

                set ::key APRS2172000
                set ::data ""

                wm protocol . WM_DELETE_WINDOW {exit}
                wm title . "Blowfish Encryption/Decipher Tool"
                wm resizable . 1 0

                label  .k -text "Key:" -anchor w
                entry  .key -show * -textvar ::key -highlightcolor yellow -highlightthickness 3

                label  .d -text "Data:" -anchor w
                entry  .data -textvar ::data -highlightcolor yellow -highlightthickness 3

                label  .m -text "Mode:" -anchor w
                ComboBox .mode -values {cbc ecb} \
                -modifycmd [list ComboUpdate .mode] \
                -autocomplete true \
                -editable false

                .mode setvalue @0        

                button .browser -text Load -command {LoadFile [tk_getOpenFile -filetypes {{"Data File"    {.key} }}]} -background blue -foreground white

                button .e -text "Encrypt Data" -command {Encrypt} -foreground blue

                button .de -text "Decipher Data" -command {Decrypt} -foreground red
                button .cancel -text Exit -command {exit} -background red

                grid   .k .key - - -sticky news
                grid   .d .data - - -sticky news
                grid   .m .mode  - - -sticky news
                grid   .e .de - - -sticky news
                grid   .browser  - - -sticky news
                grid   .cancel - - -sticky news

                grid rowconfigure . 0 -weight 1
                grid columnconfigure . 1 -weight 1

                raise .
                grab set .

                focus .data

                vwait ::data

                button .save -text "Save" -command {SaveFile} -background green

                grid   .save -  -  -sticky news


        # Event Driven. Called when the mode combobox is clicked.
        proc ComboUpdate {p} {
                global mode
                puts "ComboBox change: [$p cget -text]"
                set mode [$p cget -text]

        # Encode the data
        proc Encrypt { } {

                global data mode

                set data [blowfish::blowfish -mode $mode -dir encrypt -key SECRET $data]


        # Decode the Encrypted data
        proc Decrypt { } {

                global data mode

                set data [blowfish::blowfish -mode $mode -dir decrypt -key SECRET $data]

        # Save the data field.
        proc SaveFile { } {

                global data

                set types {
                        {"Data Files"       {.key} }

                set file [tk_getSaveFile -filetypes $types -defaultextension .key]

                # Only save the file if the user click save not cancel
                if {! [string match "" $file ]} {
                        set fileid [open $file w]
                        fconfigure $fileid -translation binary
                        puts $fileid $data
                        close $fileid  

        # Load the data field
        proc LoadFile {file} {

                global data mode

                if {[string match "" $file]} {return}

                set fileid [open $file r]
                fconfigure $fileid -translation binary
                set data [read $fileid]
                close $fileid


        # show background errors
        proc bgerror {value} {puts $value}

        # Call the main window

The Tcl Blowfish package can be found in TclLib or newer. Comments are welcome regarding the above Tcl/Tk code. Scott