ARC4(?) Stream Cipher with Random Initial Vector

[xcoder]

Print "##############################################"

global key$

code$ = "AAFFE0E1E2" 'key in hex$ format

for i = 1 to len(code$)step 2

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

byte = hexDec(chunk$)

char$ = chr$(byte)

key$ = key$ + chr$(byte)

next i

print " ARC4 Stream Cipher with Random Inital Vector"

print "Select an Option: "

print "Select (1) for Encrypt"

print "Select (2) for Decrypt"

print "Select (3) to quit"

input "Enter your choice: ";num



select case num

case 1

call Encrypt 1

case 2

call Decrypt 2

case 3

print "Goodbye!"

Stop

case else

print "Invalid input"

print "Program Terminated"

call quit

end select



print:print

print "End of Code"

End



sub Encrypt x

iv$ = iv10$()

input "File to Read: ";file$

dim info$(10,10)

if fileExists(file$) then

print file$; " exists!"

else

print file$; " doesn't exist!"

call quit

end if

open file$ for input as #1

if x = 1 then file2$ = "ENC "+file$

open file2$ for output as #2

txt$ = input$(#1,lof(#1))

print #2, Encode$(txt$,iv$);

close #1

close #2

for i = 1 to 6

print space$(i);"Encrypting"

next

print "------------completed----------------"

end sub



sub Decrypt x

input "File to Read: ";file$

dim info$(10,10)

if fileExists(file$) then

print file$; " exists!"

else

print file$; " doesn't exist!"

call quit

end if

open file$ for input as #1

if x = 2 then file2$ = "DEC "+ file$

open file2$ for output as #2

txt$ = input$(#1,lof(#1))

print #2, Decode$(txt$)

close #1

close #2

for i = 1 to 6

print space$(i);"Decrypting"

next

print " --------------completed-------------------------"

end sub





function Encode$(msg$,iv$)

print iv$ '******************

fkey$ = key$ + iv$

print fkey$ '******************

call KSA$ fkey$

out$ = PRGA$(msg$,iv$)

Encode$ = out$

end function

'============================================================

function Decode$(out$)

ivRx$ = left$(out$,10)

print ivRx$ '******************

rfkey$ = key$ + ivRx$

print rfkey$ '******************

call KSA2$ rfkey$

in$ = PRGA2$(out$)

Decode$ = in$

end function

'=============================================================



sub KSA$ fkey$

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$(fkey$,i mod len(fkey$)+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



function PRGA$(msg$,iv$)

i = 0

j = 0

for x = 1 to len(msg$) 'cannot use varible i or j

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

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

temp = S(i)

S(i) = S(j)

S(j) = temp

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

cipher = byte xor k

ascii$ = ascii$ + chr$(cipher)

next x

PRGA$ = iv$ + ascii$

end function



function iv10$()

for i = 0 to 9

x = int(rnd(1)* 256)

y$ = y$ + chr$(x)

next

iv10$ = y$

end function



'================== receive program ========================================



sub KSA2$ rfkey$

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$(rfkey$,i mod len(rfkey$)+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



function PRGA2$(msg$)

text$ = mid$(msg$,11)

i = 0

j = 0

for x = 1 to len(text$) 'cannot use varible i or j

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

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

temp = S(i)

S(i) = S(j)

S(j) = temp

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

cipher = byte xor k

ascii$ = ascii$ + chr$(cipher)

next x

PRGA2$ = ascii$

end function



sub quit

print "Goodbye!"

stop

end sub





'-----------------------------------------------------------------

function fileExists(fullPath$)

files pathOnly$(fullPath$), filenameOnly$(fullPath$), info$()

fileExists = val(info$(0, 0)) > 0

end function



function pathOnly$(fullPath$)

pathOnly$ = fullPath$

while right$(pathOnly$, 1) <> "\" and pathOnly$ <> ""

pathOnly$ = left$(pathOnly$, len(pathOnly$)-1)

wend

end function



function filenameOnly$(fullPath$)

pathLength = len(pathOnly$(fullPath$))

filenameOnly$ = right$(fullPath$, len(fullPath$)-pathLength)

end function

'-------------------------------------------------------------------

[B+]

Hey xcoder ,

Welcome to forum! Your could write books of encryption and random number generators.

Hey I wonder why moderators haven't gotten around to showing you where the code tags (to put you code in a window to take less room and to scroll) are and using the BBC tab in the forum editor (to avoid double spacing code). I think they are all playing chess ;-))

Attachments:

[B+]

So your program might look like this:


Print "##############################################"
global key$
code$ = "AAFFE0E1E2" 'key in hex$ format
for i = 1 to len(code$)step 2
   chunk$ = mid$(code$,i,2)
   byte = hexDec(chunk$)
   char$ = chr$(byte)
   key$ = key$ + chr$(byte)
next i
print " ARC4 Stream Cipher with Random Inital Vector"
print "Select an Option: "
print "Select (1) for Encrypt"
print "Select (2) for Decrypt"
print "Select (3) to quit"
input "Enter your choice: ";num
select case num
   case 1
       call Encrypt 1
   case 2
       call Decrypt 2
   case 3
       print "Goodbye!"
       Stop
   case else
       print "Invalid input"
       print "Program Terminated"
       call quit
end select
print:print
print "End of Code"
End

sub Encrypt x
   iv$ = iv10$()
   input "File to Read: ";file$
   dim info$(10,10)
   if fileExists(file$) then
       print file$; " exists!"
   else
       print file$; " doesn't exist!"
       call quit
   end if
   open file$ for input as #1
   if x = 1 then file2$ = "ENC "+file$
   open file2$ for output as #2
   txt$ = input$(#1,lof(#1))
   print #2, Encode$(txt$,iv$);
   close #1
   close #2
   for i = 1 to 6
       print space$(i);"Encrypting"
   next
   print "------------completed----------------"
end sub

sub Decrypt x
   input "File to Read: ";file$
   dim info$(10,10)
   if fileExists(file$) then
       print file$; " exists!"
   else
       print file$; " doesn't exist!"
       call quit
   end if
   open file$ for input as #1
   if x = 2 then file2$ = "DEC "+ file$
   open file2$ for output as #2
   txt$ = input$(#1,lof(#1))
   print #2, Decode$(txt$)
   close #1
   close #2
   for i = 1 to 6
       print space$(i);"Decrypting"
   next
   print " --------------completed-------------------------"
end sub

function Encode$(msg$,iv$)
   print iv$ '******************
   fkey$ = key$ + iv$
   print fkey$ '******************
   call KSA$ fkey$
   out$ = PRGA$(msg$,iv$)
   Encode$ = out$
end function

'============================================================
function Decode$(out$)
   ivRx$ = left$(out$,10)
   print ivRx$ '******************
   rfkey$ = key$ + ivRx$
   print rfkey$ '******************
   call KSA2$ rfkey$
   in$ = PRGA2$(out$)
   Decode$ = in$
end function

'=============================================================
sub KSA$ fkey$
   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$(fkey$,i mod len(fkey$)+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

function PRGA$(msg$,iv$)
   i = 0
   j = 0
   for x = 1 to len(msg$) 'cannot use varible i or j
       byte = asc(mid$(msg$,x,1))
       j = (j + S(i))mod 256
       temp = S(i)
       S(i) = S(j)
       S(j) = temp
       k = (S(i) + S(j))mod 256
       cipher = byte xor k
       ascii$ = ascii$ + chr$(cipher)
   next x
   PRGA$ = iv$ + ascii$
end function

function iv10$()
   for i = 0 to 9
       x = int(rnd(1)* 256)
       y$ = y$ + chr$(x)
   next
   iv10$ = y$
end function

'================== receive program ========================================
sub KSA2$ rfkey$
   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$(rfkey$,i mod len(rfkey$)+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

function PRGA2$(msg$)
   text$ = mid$(msg$,11)
   i = 0
   j = 0
   for x = 1 to len(text$) 'cannot use varible i or j
       byte = asc(mid$(text$,x,1))
       j = (j + S(i))mod 256
       temp = S(i)
       S(i) = S(j)
       S(j) = temp
       k = (S(i) + S(j))mod 256
       cipher = byte xor k
       ascii$ = ascii$ + chr$(cipher)
   next x
   PRGA2$ = ascii$
end function

sub quit
   print "Goodbye!"
   stop
end sub

'-----------------------------------------------------------------
function fileExists(fullPath$)
   files pathOnly$(fullPath$), filenameOnly$(fullPath$), info$()
   fileExists = val(info$(0, 0)) > 0
end function

function pathOnly$(fullPath$)
   pathOnly$ = fullPath$
   while right$(pathOnly$, 1) <> "\" and pathOnly$ <> ""
       pathOnly$ = left$(pathOnly$, len(pathOnly$)-1)
   wend
end function

function filenameOnly$(fullPath$)
   pathLength = len(pathOnly$(fullPath$))
   filenameOnly$ = right$(fullPath$, len(fullPath$)-pathLength)
end function



[B+]

I ran it and no way to tell if encrpyt works until decrypt it again.

Didn't work for me, I tried 2 x's gobblely-gook both. Maybe I need more instruction?

OK I may have been trying to decrypt wrong file. I tried 123456789 = count.txt and decrypt ENC count.txt and it worked!
Yep! Just tried the big txt file again and works too decrypt: "ENC "+ filename


Have you figured out fileDialog yet, that would make selecting files easier.

[B+]

Here is code snippet I used to check out fileDialog, maybe you can use it for file selecting in your code?

filedialog "Select file for Project Folder", "*.txt;*.bas", source$   'Filedialog test.txt b+ 2021-01-30
print source$
if source$ = "" then end  'if you cancel you quit
for i = len(source$) to 1 step -1
   if mid$(source$, i, 1) = "\" or mid$(source$, i, 1) = "/" then foundLastSlash = i :exit for
next
if foundLastSlash then filename$ = mid$(source$, foundLastSlash + 1) else filename$ = source$
for i = len(filename$) to 1 step -1
   if mid$(filename$, i, 1) = "." then foundDot = i : exit for
next
projectName$ = mid$(filename$, lastSlash + 1, foundDot - lastSlash -1)
print filename$, projectName$


This breaks down pathed file name to just filename and then without extension called projectName$

[xcoder]

print "#######################################"
global key$

randomize 0.123456789 '10^9 permutations
ctr = 0
for i = 1 to 500
y = int(rnd(1) * 256)
key$ = key$ + chr$(y)
next i

print "Select an Option: "
print "Select (1) for Encrypt"
print "Select (2) for Decrypt"
print "Select (3) to quit"
input "Enter your choice: ";num

select case num
case 1
call Encrypt 1
case 2
call Decrypt 2
case 3
print "Goodbye!"
Stop
case else
print "Invalid input"
print "Program Terminated"
call quit
end select

print
print "---------- completed ------------"
End


sub Encrypt x
filedialog "Open text file", "*.txt", file$
if file$ <> "" then
open file$ for input as #1
for i = 1 to 6
print space$(i);"Encrypting"
next i
text$ = input$(#1,lof(#1))
f$ = scramble$(text$)
close #1
file2$ = file$+"ENC"
open file2$ for output as #2
print #2,f$
close #2
else
notice "No file chosen!"
end if
end sub

sub Decrypt x
filedialog "Open text file", "*.txt", file$
if file$ <> "" then
open file$ for input as #1
for i = 1 to 6
print space$(i);"Decrypting"
next i
text$ = input$(#1,lof(#1))
f$ = unScramble$(text$)
close #1
file2$ = file$+"DEC"
open file2$ for output as #2
print #2,f$
close #2
else
notice "No file chosen!"
end if
end sub

function scramble$(text$)
for i = 1 to len(text$)
byte = asc(mid$(text$,i,1))
keyer = asc(mid$(key$,i mod len(key$)+1))
cipher$ = cipher$ + chr$(byte xor keyer)
next i
scramble$ = cipher$
end function

function unScramble$(text$)
for i = 1 to len(text$)
byte = asc(mid$(text$,i,1))
keyer = asc(mid$(key$,i mod len(key$)+1))
cipher$ = cipher$ + chr$(byte xor keyer)
next i
unScramble$ = cipher$
end function

sub quit
timer 1000,[done]
wait
[done]
timer 0
End
end sub