Here is a program that applies Vigenère's encryption method [L1 ] to files.
At first It transposes inputs to base 64 encoding [L2 ], then it applies Vigenere's method.
# vigenere.tcl --
#
# provide method to encrypt and decrypt a file following vigenere algorithm.
#
# encrypt read from a input stream and write encrypted data to an output stream.
# decrypt read from a encrypted input stream and write decrypted (clear) data to an output stream.
# streams should be "fconfigure"'d with "-translation binary" option.
#
# Copyright (c) 2009 Laurent Gateau.
#
# version 1.0
#
package require base64
namespace eval vigenere {
namespace export Encrypt Decrypt EncryptFile DecryptFile
variable alphabet64 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
variable bufferlen 72
variable version "1.0"
}
# vigenere::engine --
#
# Arguments:
# key and data variables must be part of alphabet64 (i.e. : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" and optionnaly "=")
# key and data variables might result from ::base64::encode calls
# encode must be either 1 (encode) or 0 (decode)
#
# Results:
# result is a cyphered string containing symbols from alphabet64
#
proc vigenere::engine { key data {encode -encode}} {
variable alphabet64
set result ""
set ii 0
set keylen [string length $key]
while {$ii < [string length $data]} {
set car [string index $data $ii]
if {$encode && ($car == "=")} {
incr ii
continue
}
set keyii [expr $ii % $keylen]
set keycar [string index $key $keyii]
set index1 [string first $car $alphabet64]
set index2 [string first $keycar $alphabet64]
if {$encode} {
set jj [expr ($index1 + $index2) % 64]
} else {
set jj [expr ($index1 - $index2) % 64]
}
append result "[string index $alphabet64 $jj]"
incr ii
}
return $result
}
# vigenere::encode --
#
# Arguments:
# key and data variables must be part of alphabet64 (i.e. : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" and optionnaly "=")
# key and data variables might result from ::base64::encode calls
#
# Results:
# result is a cyphered string containing symbols from alphabet64
#
proc vigenere::encode { key data } {
return [vigenere::engine "$key" "$data" 1]
}
# vigenere::decode --
#
# Arguments:
# key and data variables must contains only symbol from alphabet64 (i.e. : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" and optionnaly "=")
# key variable might result from a call of ::base64::encode
#
# Results:
# result is a clear string containing symbols from alphabet64
# result might be a parameter given to a call of ::base64::decode
#
proc vigenere::decode { key data } {
return [vigenere::engine "$key" "$data" 0]
}
# vigenere::encrypt --
#
# Arguments:
# key is a pass phrase ; the longer the better secrets are kept.
# fin is the input stream
# fout is the output stream
# Results:
# fin has reached its end
# fout has been written with encrypted data
#
proc vigenere::encrypt { key fin fout } {
variable bufferlen
while { ! [eof $fin] } {
set input [read $fin $bufferlen]
set data [::base64::encode -maxlen [expr $bufferlen * 4 / 3] $input]
puts $fout [::vigenere::encode [::base64::encode "$key"] "$data"]
}
}
# vigenere::decrypt --
#
# Arguments:
# key is a pass phrase ; the longer the better secrets are kept.
# fin is the input stream
# fout is the output stream
#
# Results:
# fin has reached its end
# fout has been written with decrypted (clear) data.
#
proc vigenere::decrypt { key fin fout } {
while { ! [eof $fin] } {
set input [gets $fin]
set data [::vigenere::decode [::base64::encode "$key"] "$input"]
puts -nonewline $fout [::base64::decode "$data"]
}
}
# vigenere::command --
#
# Arguments:
# command line arguments : arc and argv
# mode is either -encrypt or -decrypt
# key is the cypher key
# input file name
# output file name
#
# Results:
# write output file or display usage.
#
proc vigenere::command {} {
global argc argv
if { $argc > 0 } {
set mode [lindex $argv 0]
set key [lindex $argv 1]
switch -exact -- $mode {
-encrypt {
set fin [open [lindex $argv 2] "r"]
fconfigure $fin -translation binary
set fout [open [lindex $argv 3] "w"]
fconfigure $fout -translation binary
encrypt "$key" $fin $fout
}
-decrypt {
set fin [open [lindex $argv 2] "r"]
fconfigure $fin -translation binary
set fout [open [lindex $argv 3] "w"]
fconfigure $fout -translation binary
decrypt "$key" $fin $fout
}
default {
puts "usage: (-encrypt|-decrypt) key input_file output_file"
}
}
}
}
package provide vigenere $::vigenere::version
vigenere::command
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