Crypt String with Xor

[Droopy]

Code updated for 5.20+

Just a simple encoding with Xor

Code: Select all

Procedure.s XorCrypt(Key.s,String.s)
  
  For n=1 To Len(String)
    ChrString=Asc(Mid(String,n,1))
    ChrKey=Asc(Mid(Key,Ptr+1,1))
    If ChrString=ChrKey
      ChrCrypt=ChrString
    Else
      ChrCrypt=ChrString ! ChrKey
    EndIf
    
    Retour.s+Chr(ChrCrypt)
    Ptr+1
    If Ptr >Len(Key) : Ptr=0 : EndIf
  Next
  ProcedureReturn Retour
EndProcedure

Test with this :

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Key.s="This is the Key"
xx.s= XorCrypt(Key,"This is the String to Crypt")
Debug xx
Debug XorCrypt(Key,xx)

[Shannara]

Result is:

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This is the i:IOI0R
This is the String to Crypt

This code only encrypts a peice of the string and not the whole thing.[/code]

[Dare2]

Result is:

Code: Select all

This is the i:IOI0R
This is the String to Crypt

This code only encrypts a peice of the string and not the whole thing.[/code]

At a guess, that is because the unencrypted characters match (key=value) and so the test avoids this otherwise there would be a null (0) terminator embedded into the middle of the string.

[Droopy]

Yes a XOR between 2 same code = 0 = end string !!

You must select a good password

[Dare2]

Self encrypt/decrypt (is own key) with Xor.

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Procedure.s selfE(src.s,en.l)
  k1=Len(src)
  If k1>0
    *p=@src
    k2=PeekB(*p) & $FF
    r=k1 ! k2
    If r<>0 : PokeB(*p,r) : EndIf
    For i=2 To Len(src)
      *p+1
      If en : k1=PeekB(*p-1) & $FF : Else : k1=k2 : EndIf
      k2=PeekB(*p)
      r=k1 ! k2
      If r<>0 : PokeB(*p,r) : EndIf
    Next
  EndIf
  ProcedureReturn src
EndProcedure

w.s="Wooo! Hooo! This is self encrypting"
x.s=selfE(w,#True)
y.s=selfE(x,#False)
Debug w
Debug x
Debug y

[pthien]

The self-encrypting code doesn't seem to work, my debug output is:

Wooo! Hooo! This is self encrypting
瑴ᬛ瑴ᬛ㨺ᨚ剒㴽剒㴽ᰜ㰼桨桨ā牲剒;s self encrypting
瑗᭯瑯᭯㨡ᨠ剈㵯副㵯ᰡ㰠桔桨ũ牳删is self encrypting

I'm using 6.04LTS Windows x86, if that is important.

Any ideas?

If I'm reading the code correctly, this seems to encrypt each character using the previous character, and stores the starting character required with the encrypted string?

[Taz]

here you go, without poke, and with Unicode support

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EnableExplicit

Procedure.s selfE(src.s, en.b = #True)
	Protected i.i, k1.i, k2.i, r.i, *p.Character = @src, srcLen.i = Len(src)

	If srcLen
		k2 = *p\c
		r = srcLen ! k2
		If r
			*p\c = r
		EndIf
		For i=2 To srcLen
			*p + SizeOf(Character)
			If en
				k1 = PeekC(*p - SizeOf(Character))
			Else
				k1 = k2
			EndIf
			k2 = *p\c
			r = k1 ! k2
			If r
				*p\c = r
			EndIf
		Next
	EndIf
	ProcedureReturn src
EndProcedure

Define Text.s = "Wooo! Hooo! This is self encrypting"
Define x.s = selfE(Text)
Define y.s = selfE(x, #False)

Debug "Text["+Text+"]"
Debug "   x["+x+"]"
Debug "   y["+y+"]"

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Text[Wooo! Hooo! This is self encrypting]
   x[tt:R=R=<hhrR;Hh~tT1_<N7G3Z4S]
   y[Wooo! Hooo! This is self encrypting]

[pthien]

Oh thank you Taz!

I completely forgot about unicode again.