; example :
key$="PutYourKeyHere"
EncryptFile("original.txt","encrypted.txt",key$)
DecryptFile("encrypted.txt","decrypted.txt",key$)
; functions :
Function EncryptFile(in$,out$,k$)
filein = ReadFile(in$)
fileout = writeFile(out$)
s$=""
while not eof(filein)
s$=s$+chr(ReadByte( filein ))
wend
backwards=false
for i%=1 to len (s$)
c$=Mid(s$,i%,1)
a%=asc(c$)
j%=i%
while j%>len(k$)
j%=j%-len(k$)
wend
if backwards then j%=len(k$)-j%+1
if j=1 then backwards=false
if j=len(k) then backwards=true
kc$=Mid(k$,j%,1)
ka%=asc(kc$)
enc%=ka%+a%
writeshort(fileout,enc)
next
closefile filein
closefile fileout
end function
function DecryptFile(in$,out$,k$)
filein = ReadFile(in$)
fileout = writeFile(out$)
i=0
backwards=false
while not eof(filein)
i=i+1
;s$=s$+chr(ReadByte( filein ))
enc%=readshort(filein)
j%=i%
while j%>len(k$)
j%=j%-len(k$)
wend
if backwards then j%=len(k$)-j%+1
if j=1 then backwards=false
if j=len(k) then backwards=true
kc$=Mid(k$,j%,1)
ka%=asc(kc$)
a%=enc%-ka%
writebyte fileout,a%
wend
closefile filein
closefile fileout
end function |