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Crypto Letters and Numbers

Posted on 2012-03-30
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Last Modified: 2012-03-30
hello
I would like to know how to change the encryption algorithm below for it to return only letters and numbers?

function EncryptDecrypt(InpStr, PassPhrase: string; Salt: Integer): string;
var
  iIndex: Integer;
  pIndex: Integer;
begin
  pIndex := 1;

  for iIndex := 1 to Length(InpStr) do
  begin
      InpStr[iIndex] := Chr(Salt XOR Ord(PassPhrase[pIndex]) XOR Ord(InpStr[iIndex]));
      Inc(Salt);
      Inc(pIndex);

      if (pIndex > Length(PassPhrase)) then
         pIndex := 1;
  end;

  Result := InpStr;
end;

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thanks
Wagner
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Question by:wagnerlimalopes
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4 Comments
 
LVL 19

Expert Comment

by:Thommy
ID: 37787229
If you change encryption, you will have to change decryption, too!!!
0
 

Author Comment

by:wagnerlimalopes
ID: 37787363
even having to separate the encryption and decryption codes, what is the solution?

wagner
0
 
LVL 27

Assisted Solution

by:Sinisa Vuk
Sinisa Vuk earned 250 total points
ID: 37787405
Do simple base64 encode after you do encrypt and base64 decode before you do decrypt.

http://www.swissdelphicenter.ch/torry/showcode.php?id=1524

http://www.delphipraxis.net/991-base64-mime-en-decoding.html
0
 
LVL 22

Accepted Solution

by:
Ferruccio Accalai earned 250 total points
ID: 37787440
Thommy, sometimes I don't understand your comments.
The function posted by him recursively crypts or decrypts a string giving a pass string and a salt.
@wagnerlimalopes: what is the solution?
I guess there's not solution for what you're asking, using this kind of function, as any parameter you pass could be so variable that it could result in at least one non standard alphanumeric character
To get what you need you should use another kind of encryption/decryption script, or insert some other code to force the range of any character into the alphanumeric range
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