Real RC4 Stream Encryption

[xcoder]

'Text Encryption Real RC4 stream cipher

'Use a Pass Word as the Key

' Just paste text into the texteditor and press encrypt button

nomainwin

BackgroundColor$ = "darkcyan"

ForegroundColor$ = "black"

global key$, key2$

WindowWidth = 600 : WindowHeight = 400

UpperLeftX=int((DisplayWidth-WindowWidth)/2)

UpperLeftY=int((DisplayHeight-WindowHeight)/2)

texteditor #main.text, 200, 20, 360, 320

button #main.enc, "Encrypt", [encrypt], ul, 55, 155, 110, 25

button #main.dec, "Decrypt", [decrypt], ul, 55, 195, 110, 25

button #main.clearKey , "Clear Key", [clearKey], ul, 30, 75, 70, 20

button #main.dec , "Clear Text", [clearText], ul, 110, 75, 70, 20

button #main.refresh , "Delete Encrypted File", [refresh], ul, 40, 240, 135, 25

button #main.copytext , "Copy Text", [copytext], ul, 75, 105, 60, 25

textbox #main.key, 30, 45, 150, 20

statictext #main.editor, "Type or Paste Text Here", 335, 5, 190, 15

statictext #main.encKey, "Encryption Key ", 20, 30, 170, 15

Open "Real RC4 Stream Encryptor " for window as #main

#main "trapclose [quit]"



key$ = "MyFavoritePassWord" ''' default key if none entered

#main.key key$

#main.text "!autoresize"

if fileExists(DefaultDir$, "textEditor") then

open "textEditor" for input as #1

#main.text , text$ 'read from textEditor

close #1

#main.text "!origin 0 0" 'reset cursor

end if



wait

[encrypt]

#main.key "!contents? key$"

if key$ = "" then [advise]

#main.text "!contents? text$" ' read from textEditor

text$ = trim$(text$)

call keyPass '''^^^^^^^^^^^^^ modified

call KSA

alpha$ = txPRGA$(text$) '***** encrypt



#main.text "!cls"

#main.text alpha$ 'write to textEditor

open "textEditor" for output as #1

#1 alpha$

close #1

#main.text "!origin 0 0" 'reset cursor



wait

[decrypt]

#main.key "!contents? key$"

if key$ = "" then [advise]

#main.text "!contents? text$" 'read from textEditor

text$ = trim$(text$)

call keyPass '''^^^^^^ modified

call KSA

bravo$ = hex2Text$(text$) '***** decrypt



#main.text "!cls"

#main.text bravo$ 'write to textEditor

open "textEditor"for output as #1

#1 bravo$

close #1

#main.text "!origin 0 0" 'reset cursor



wait

[clearKey]

#main.key ""

wait

[clearText]

#main.text "!cls"

wait

[refresh]

if fileExists(DefaultDir$, "textEditor") then kill DefaultDir$;"\textEditor"

#main.text "!cls"

wait

[copytext]

#main.text "!selectall"

#main.text "!copy"

wait

[quit]

close #main

End

[advise]

notice "Key is required"

close #main

End



print "------------------------------------------------------------------------------------------------------------"



'function for checking file existence

function fileExists(path$, filename$)

dim info$(0, 0)

files path$, filename$, info$()

fileExists = val(info$(0, 0)) 'non zero is true

end function



sub keyPass '''^^^^ modified to accept keyboard characters

print "ascii value"

key2$ = key$ '''^^^^ global string variables

for i = 1 to len(key2$)

byte = asc(mid$(key2$,i,1))

print byte

next i

print key2$ '''mainwin testing

print

end sub



sub KSA '''''key expansion ^^^^^^^^^^^

dim S(256)

dim K(256)

i = 0: j = 0

for i = 0 to 255

S(i)= i

next i

for i = 0 to 255

K(i)= asc(mid$(key2$,i mod len(key2$)+1))

next i

for i = 0 to 255

j = (j+ S(i)+ K(i))mod 256

temp = S(i)

S(i)= S(j)

S(j)= temp

next i

end sub



print "############## Encryption Functions ##################"



function txPRGA$(inString$) '''''psuedo random byte generator

i = 0: j = 0

for x = 1 to len(inString$)

i = (i + 1) mod 256 '********

byte = asc(mid$(inString$,x,1))

j = (j + S(i))mod 256

temp = S(i)

S(i) = S(j)

S(j) = temp

t = (S(i) + S(j))mod 256 '''real RC4

k = S(t) ''' real RC4

ck = byte xor k ''' real RC4

char$ = char$ + chr$(ck) ''' real RC4

next x

txPRGA$ = text2Hex$(char$)

end function



function text2Hex$(cipher$)

for i = 1 to len(cipher$) 'encrypted text

byte = asc(mid$(cipher$,i,1)) 'encrypted ascii

hex$ = decHex$(byte)

hex$ = right$("0" + hex$,2)

max$ = max$ + hex$ 'encrypted hex

next i

text2Hex$ = max$

end function



print "############# Decryption functions ###############"



function hex2Text$(hex$)

for i = 1 to len(hex$)step 2 'encrypted hex

chunk$ = mid$(hex$,i,2)

byte = hexDec(chunk$) 'encrypted ascii

text$ = text$ + chr$(byte) 'encrypted text

next i

hex2Text$= rxPRGA$(text$)

end function



function rxPRGA$(inString$) '''^^^^psuedo random byte generator

i = 0: j = 0

for x = 1 to len(inString$)

i = (i + 1) mod 256 '**********

byte = asc(mid$(inString$,x,1))

j = (j + S(i))mod 256

temp = S(i)

S(i) = S(j)

S(j) = temp

t = (S(i) + S(j))mod 256 ''' real RC4

k = S(t) ''' real RC4

ck = byte xor k ''' real RC4

char$ = char$ + chr$(ck) ''' real RC4

next x

rxPRGA$ = char$

end function