Hi guys,
I have being trying to implement RSA in a network. the encryption is fine except for the decryption (I will fix that soon as I want to see what the encrypted message looks like unencrypted). The problem is that the Public key exchange returns a 0 and the encryption has a 'integer divide by 0' error when dubuged by visual studio. Can someone suggest an improvement on the key exchange at lines 123 and 235 or notify me if you see any flaws in the algorithm itself.
;create a type to save message data
Type message
Field cont$
Field from
Field Too
Field tpe
End Type
msg$ = ""
host = False
;infomation about players
Type players
Field name$
Field id
Field keyn
Field keyk
Field r
Field g
Field b
End Type
;make the main window
window = CreateWindow ("IM Program",250,100,800,600,0,15)
SetMinWindowSize window,800,600
timer = CreateTimer (60)
Gosub createname
;error checking for creating the net game and player
.creategame
gamemain = StartNetGame ()
playerid = CreateNetPlayer (plname$)
If gamemain < 1 Then Goto creategame
If gamemain = 1 Then
Gosub joinencrypt
te.message = New message
te\cont = "Succesfully joined session"
EndIf
If gamemain = 2
te.message = New message
te\cont = "Succesfully hosted session on " + DottedIP (HostIP (CountHostIPs ("")))
Gosub hostencrypt
EndIf
If playerid = 0
Gosub createname
Else
te.message = New message
te\cont = "User '" + plname$ + "' was created"
End If
;main chat interface
canvas = CreateCanvas (20,20,560,440,window)
panel = CreatePanel (600,20,180,490,window,1)
sendbt = CreateButton ("Send",480,480,50,30,window)
imput = CreateTextArea (160,470,300,50,window)
SetBuffer CanvasBuffer (canvas)
SetPanelColor panel,255,255,255
SetGadgetLayout canvas,1,2,1,2
SetGadgetLayout panel,2,1,1,2
;main loop
Repeat
WaitEvent (1)
If EventID () = $803 Then Gosub leave
;send messages if send button is pressed
If EventSource () = sendbt Then Gosub sendfunc
;check for messages
If RecvNetMsg() = True Gosub checkboard
;Print the messages on the screen
r = 1
For te.message = Each message
Text 10,10 * r,te\cont
r = r + 1
Next
;draw everything and wait 40 millisecs
FlipCanvas canvas
Delay 40
Forever
;set player name
Goto skipcreatename
.createname
;gui elements
lab1 = CreateLabel ("Enter Name",170,200,70,20,window)
pname = CreateTextField (250,200,150,20,window)
but1 = CreateButton ("Go",410,200,40,20,window,4)
;wait for a button press
Repeat
WaitEvent (1)
If EventID () = $803 Then End
If EventSource () = but1 And TextFieldText (pname) <> "" Then Exit
Delay 40
Forever
;get the name
plname$ = TextFieldText$ (pname)
;clear the screen
FreeGadget lab1
FreeGadget pname
FreeGadget but1
.skipcreatename
Return
;recive message functions
Goto skiprec
.checkboard
;capture the message as it could change
msg$ = NetMsgData$ ()
from = NetMsgFrom ()
too = NetMsgTo ()
tpe = NetMsgType ()
;type 1 = unencrypted
If tpe = 1
te.message = New message
te\cont$ = msg$
te\from = from
te\too = too
te\tpe = tpe
EndIf
;type 2 = key exchange
If tpe = 2 And Left$ (msg$,10) = "CRYPTOKEY "
For counter = 1 To (10 - Len (msg$))
If Mid (msg$,counter + 10,1) = " " Then space = counter + 10
Next
qt.players = New players
qt\id = from
qt\keyn = Mid (msg$,10,space)
qt\keyk = Mid (msg$,space,space - Len (msg$))
qt\name$ = NetPlayerName$ (from)
If qt\keyk <> 0 And qt\keyn <> 0
te.message = New message
te\cont = "Key acquired from " + NetPlayerName$ (from)
EndIf
SeedRnd MilliSecs ()
Delay Rnd (600)
SendNetMsg (3,"CRYPTOKEY " + n + " " + k,playerid,from)
te.message = New message
te\cont = "Key acquired from " + NetPlayerName$ (from)
EndIf
;type 4 = encrypted message
;If tpe = 4 And Left (msg$,6) = "stream"
; counter = Right (msg$,1)
; Dim incoming (counter,1)
; c = 0
; loex = 0
; Repeat
;
; If RecvNetMsg () = True
; incoming (c,0) = NetMsgData$ ()
; c = c + 1
; EndIf
; If c => counter Then loex = 1
;
; Until loex <> 0
; For c = 0 To counter
; pl = incoming(c,0) ^ j
; incoming (c,1) = pl Mod n
; Next
; For c = 0 To counter
; msg$ = msg$ + Chr (incoming(c,1))
; Next
; te.message = New message
; te\cont = msg$
;EndIf
;type 102 = change of host
If tpe = 102
te.message = New message
te\cont = "You are now the host of this session"
EndIf
;type 200 = something bad happened
If tpe = 200 Then Gosub quit
.skiprec
Return
;send message functions
Goto skipsend
.sendfunc
msg$ = TextAreaText$ (imput)
leg = Len (msg$)
If msg$ = "" Then Goto skipsend
;display the message
te.message = New message
te\cont$ = plname$ + ": " + msg$
;break the message up
Dim msgarr (leg,1)
For counter = 1 To leg
msgarr (counter,0) = Mid (msg$,counter,1)
Next
;send the message to each user encrypted with their keys
For qt.players = Each players
For counter = 1 To leg
emsg = msgarr (counter,0) ^ qt\keyk
msgarr (counter,1) = emsg Mod qt\keyn
Next
For counter = 1 To leg
msg$ = msg$ + msgarr (counter,1)
Next
SendNetMsg (1,msg$,playerid,qt\id)
Next
SetTextAreaText imput,""
.skipsend
Return
Goto skiphostenc
.hostencrypt
SeedRnd MilliSecs ()
checktime = 50
;key generation
p = Rnd (10,20)
q = Rnd (10,20)
n = p * q ;public key
z = (p - 1) * (q - 1)
.createkh
k = Rnd (1,10);public key
;If test <> Floor (test) Then Goto createkh
j = (z + 1) / k;private key
te.message = New message
te\cont = "Generated public keys n:" + n + " and k:" + k
te.message = New message
te\cont = "And private key j:" + j
hostcont = True
.skiphostenc
Return
Goto skipjoinencrypt
.joinencrypt
SeedRnd MilliSecs ()
checktime = 50
;key generation
p = Rnd (10,20)
q = Rnd (10,20)
n = p * q ;public key
z = (p - 1) * (q - 1)
.createkj
k = Rnd (1,10);public key
;If test <> Floor (test) Then Goto createkj
j = (z + 1) / k;private key
SendNetMsg (1,plname$ + " has joined",playerid,0)
Delay 40
;send the public keys away
SendNetMsg (2,"CRYPTOKEY " + n + " " + k,playerid,0)
te.message = New message
te\cont = "Generated public keys n:" + n + " and k:" + k
te.message = New message
te\cont = "And private key j:" + j
timer = 1000
tim = 0
;public key capture
Repeat
If RecvNetMsg () = True And NetMsgType () = 3
For counter = 1 To (10 - Len (msg$))
If Mid (msg$,counter + 10,1) = " " Then space = counter + 10
Next
qt.players = New players
qt\id = NetMsgFrom ()
qt\keyn = Mid (msg$,10,space)
qt\keyk = Mid (msg$,space,space - Len (msg$))
qt\name$ = NetPlayerName$ (NetMsgFrom ())
EndIf
If timer < 0 Then tim = 1
timer = timer - 1
Delay 1
Until tim <> 0
hostcont = False
.skipjoinencrypt
Return
;leave the session
Goto skipleave
.leave
SendNetMsg (1,plname$ + " has left",playerid,0)
DeleteNetPlayer playerid
End
.skipleave
Return
;force quit
Goto skipquit
.quit
Notify "Unknown Network Error",1
End
.skipquit
Return
End
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