Dateien verschlüsseln - aber wie?

[daniel-volk]

Ein Mann, ein Wort...

Hier ist der veränderte Code:

Delphi-Quellcode:

const
  EXTENSION = '.cryptmaster';
  APPNAME = 'CryptMaster';
  APPVER = 'Beta 1';
  DefCipherClass : TCipherClass = TCipher_Rijndael;
  DefHashClass : THashClass = THash_SHA1;
  DefStringFormat = fmtMIME64;
  DefCipherMode = cmCTS;
  CipherTextBegin = '[BEGIN-CryptMaster-Message]';
  CipherTextEnd = '[CryptMaster-Message-END]';

implementation

{$R *.dfm}

// Function zum Generieren der Zufallswerte
function TFrmCipher.RandomString(Len: Integer): String;
begin
  SetLength(Result, Len);
  Rnd.Buffer(Result[1], Len);
end;

// function zum Verschlüsseln von Text
function TFrmCipher.EncodeString(Klartext, Passwort : string) : string;
var
  Hashstring : string;
begin
  with DefCipherClass.Create('',nil) do
    begin
      try
       Mode := DefCipherMode;
       HashClass := DefHashClass;
       InitKey(Passwort,nil);
       Klartext := RandomString(BufSize)+Klartext;
       with DefHashClass.Create(nil) do
         begin
           try
             Hashstring := CalcString(Klartext,nil,DefStringFormat);
           finally
             Free;
           end;
         end;
       Klartext := Hashstring+Klartext;
       Result := CodeString(Klartext,paEncode,DefStringFormat);
     finally
       Free;
     end;
   end;
  // Marker für den Ciphertext setzen
  Result := CipherTextBegin+Result+CipherTextEnd;
end;

// String dekodieren | Result[1] (0,1) gibt an, ob es einen Fehler gab
function TFrmCipher.DecodeString(Ciphertext,Passwort : string):string;
var
  Hashlength : word;
  OldHash, NewHash : string;
  RemBufSize : Int64;
begin
  // Marker für den Ciphertext entfernen
  Delete(Ciphertext,1,pos(CipherTextBegin,Ciphertext)+length(CipherTextBegin)-1);
  Delete(Ciphertext,pos(CipherTextEnd,Ciphertext),length(Ciphertext)-pos(CipherTextEnd,Ciphertext)+1);
  with DefHashClass.Create(nil) do
    begin
       try
         Hashlength := length(CalcString(Ciphertext,nil,DefStringFormat));
       finally
         Free;
       end;
     end;
  with DefCipherClass.Create('',nil) do
    begin
      try
       Mode := DefCipherMode;
       HashClass := DefHashClass;
       InitKey(Passwort,nil);
       Result := CodeString(Ciphertext,paDecode,DefStringFormat);
       RemBufSize := BufSize;
      finally
       Free;
      end;
     end;
  OldHash := Copy(Result,1,Hashlength);
  Delete(Result,1,Hashlength);
  with DefHashClass.Create(nil) do
    begin
       try
         NewHash := CalcString(Result,nil,DefStringFormat);
       finally
         Free;
       end;
     end;
  Delete(Result,1,RemBufSize);
  If OldHash = NewHash then Result := '1'+Result else Result := '0'+Result;
end;

MfG,
Daniel.