Saran

Bab 5 Kesimpulan dan Saran

5.2 Saran

Untuk pengembangan lebih lanjut dari perangkat lunak ini maka penulis memberikan saran-saran sebagai berikut :

1. Proses penyisipan pesan pada aplikasi ini membutuhkan waktu yang cukup lama. Penulis menyarankan untuk mengembangkan algoritma yang lebih efisien dalam proses penyisipan pesan, karena algoritma yang digunakan pada aplikasi ini masih sederhana.

2. Untuk kedepannya diharapkan agar pesan yang disisipkan dapat dalam bentuk media digital lainnya, tidak hanya pada teks saja.

3. Perlu adanya perbaikan pada antarmuka aplikasi agar lebih bersahabat dengan pengguna. Khususnya perlu ditambahkan progress bar untuk memberitahukan waktu respon yang dibutuhkan pengguna.

DAFTAR PUSTAKA

Ariyus, Dony. 2007. Keamanan Multimedia. Yogyakarta : Penerbit Andi.

Ariyus, Dony. 2008. Pengantar Ilmu Kriptografi, Teori, Analisis dan Implementasi. Yogyakarta : Penerbit Andi.

Bender, W., Gruhl, D., Morimoto, N. et al. 1996. Techniques For Data Hiding, IBM

Systems Journal, Vol. 35, Nos 3&4, 1996. http://www.almaden.ibm.com

/cs/people/dgruhl/313.pdf. Diakses tanggal 16 Mei 2009.

Cvejic, Nedeljko. 2004. Algorithms for Audio Watermarking and Steganography. Oulu : Oulu University Press.

Daemen, J. dan Rijmen, V. 1999. AES Proposal: Rijndael. http://csrc.nist.gov/ archive/aes/ rijndael/Rijndael-ammended.pdf. Diakses tanggal 15 Mei 2009

Forouzan, Behrouz A. 2008. Cryptography and Network Security. Singapura : Mc Graw Hill.

Hartono, Jogiyanto. 2005. Analisis dan Desain Sistem Informasi : Pendekatan

Terstruktur Teori dan Praktik Aplikasi Bisnis. Yogyakarta : Penerbit Andi

Kurniawan, Yusuf. 2004. Kriptografi, Keamanan Internet dan Jaringan Komunikasi. Bandung : Informatika.

Krenn, J.R. 2004. Steganography and Steganalysis. http://www.krenn.nl/univ/ cry/steg/ article.pdf. Diakses tanggal 16 Mei 2009.

Madcoms. 2002. Pemrograman Borland Delphi 7. Madiun : Penerbit Andi.

Rassol, Raissi. 2002. The Theory Behind MP3. http://www.mp3-tech.org/ programmer/docs/ mp3_theory.pdf. Diakses tanggal 16 Mei 2009.

Vembrina, Yus Gias. Spread Spectrum Steganography. http://www.informatika.org/ ~rinaldi/Kriptografi/2006-2007/Makalah2/Makalah-007.pdf. Diakses tanggal

Wahana Komputer. 2003. Pemrograman Borland Delphi 7.0. Yogyakarta : Penerbit Andi.

http://achmadz.blogspot.com Diakses tanggal 17 Oktober 2009 http://id.wikipedia.org/wiki/CRC Diakses tanggal 30 Desember 2009

LAMPIRAN A: LISTING PROGRAM

unit uMP3; interface uses

SysUtils, Windows, Messages, Classes; //mp3 header frame type TRawMP3Header = record AudioVersion, LayerIdx, Protection, BitrateIdx, SamplingRateIdx, Padding, PrivateBit, ChannelMode, ModeExt, Copyright, Original, Emphasis: Integer; end;

//array untuk frame header MP3 type

TMP3HeaderArray = array[0..3] of byte; //Tabel bitrate (bps)

const

bmpeg1: array[1..14, 1..3] of Word = ( (32, 32, 32), (40, 48, 64), (48, 56, 96), (56, 64, 128), (64, 80, 160), (80, 96, 192), (96, 112, 224), (112, 128, 256), (128, 160, 288), (160, 192, 320), (192, 224, 352), (224, 256, 384), (256, 320, 416), (320, 384, 448));

//Tabel Sampling Rate (Hz) const

samplingRate: array[0..3] of integer = ( 44100, 48000, 32000, 0);

//Tabel sampling per frame const

samplingPerFrame: array[1..3] of Integer = ( 1152, 1152, 384);

function FindFirstHeader(filename: string): Integer;

function FindNextFrame(filename: string; prevHeaderPos: Integer; prevHeader: TMP3HeaderArray): Integer;

function getMP3Header(filename: string; pos: Integer): TMP3HeaderArray;

function frameSize(headerArray: TMP3HeaderArray): Integer; function isAvailableToSteg(filename: string; framePos: Integer; length: Integer): Boolean;

function isStegged(filename: string; framePos: Integer): Boolean; function FrameCount(filename: string): Integer;

function MaxStegSize(filename: string; length: Integer): Integer; function FileSize(FileName : String) : Int64;

function HideFile(mp3File:string; hiddenFile: string; resultFile: string; length: Integer): Integer;

function RevealFile(mp3File:string): string;

procedure Split(const Delimiter: Char; Input: string; const Strings: TStrings);

function LeftPad(S: string; Ch: Char; Len: Integer): string; implementation

//function untuk mendapatkan lokasi frame pertama function FindFirstHeader(filename: string): Integer; var

filemp3: File;

headerArray: array[0..3] of byte; count, pos: Integer;

begin Result:=-1; if FileExists(filename) then begin AssignFile(filemp3, filename); FileMode:=fmOpenRead; Reset(filemp3,1);

//looping sampai dapat header file pos:=0;

while not eof(filemp3) do begin

seek(filemp3, pos);

BlockRead(filemp3, headerArray, 4, count);

if ((headerArray[0]=$FF) and ((headerArray[1]=$FB) or (headerArray[1]=$FA))) then begin Result:=pos; break; end else begin pos:=pos+1; end; end; CloseFile(filemp3); end else begin exit; end; end;

//function untuk mendapatkan frame selanjutnya

function FindNextFrame(filename: string; prevHeaderPos: Integer; prevHeader: TMP3HeaderArray): Integer; var filemp3: File; count: Integer; posNow: Integer; headArray: TMP3HeaderArray; begin if FileExists(filename) then begin AssignFile(filemp3, filename);

FileMode:=fmOpenRead; Reset(filemp3, 1);

posNow:=prevHeaderPos+FrameSize(prevHeader); while not eof(filemp3) do

begin

seek(filemp3, posNow);

BlockRead(filemp3, headArray, 4, count);

if ((headArray[0]=$FF) and ((headArray[1] and $E0)=$E0) and ((headArray[2] and $F0)<>$F0)) then

begin Result:=posNow; break; end else begin posNow:=posNow+1; end; end; CloseFile(filemp3); end else begin exit; end; end;

//function untuk parsing mp3 header

procedure ParseHeaderArray(headerArray: TMP3HeaderArray; var RawHeader: TRawMP3Header); begin RawHeader.AudioVersion:=(headerArray[1] shr 3) and $3; RawHeader.LayerIdx:=(headerArray[1] shr 1) and $3; RawHeader.Protection:=(headerArray[1] and $1); RawHeader.BitrateIdx:=(headerArray[2] shr 4) and $F; RawHeader.SamplingRateIdx:=(headerArray[2] shr 2) and $3; RawHeader.Padding:=(headerArray[2] shr 1) and $1; RawHeader.PrivateBit:=(headerArray[2] and 1); RawHeader.ChannelMode:=(headerArray[3] shr 6) and $3; RawHeader.ModeExt:=(headerArray[2] shr 4) and $3; RawHeader.Copyright:=(headerArray[2] shr 3) and $1; RawHeader.Original:=(headerArray[2] shr 2) and $1; RawHeader.Emphasis:=(headerArray[2] and 1); end;

//function untuk mendapatkan mp3 header dari current pos function getMP3Header(filename: string; pos: Integer): TMP3HeaderArray; var filemp3: File; headerArray: TMP3HeaderArray; count: integer; begin if FileExists(filename) then begin AssignFile(filemp3, filename); FileMode:=fmOpenRead; Reset(filemp3,1); seek(filemp3, pos);

end else begin exit; end; end;

//function untuk mengetahui ukuran frame

function frameSize(headerArray: TMP3HeaderArray): Integer; var myRawMP3Header: TRawMP3Header; begin ParseHeaderArray(headerArray, myRawMP3Header); Result:=trunc(samplingPerFrame[myRawMP3Header.LayerIdx]/ 8 * bmpeg1[myRawMP3Header.BitrateIdx][myRawMP3Header.LayerIdx] * 1000 / samplingRate[myRawMP3Header.SamplingRateIdx] + myRawMP3Header.Padding); end;

//function untuk mengecek apakah sebuah frame mengandung pesan rahsia function isStegged(filename: string; framePos: Integer): Boolean; var

filemp3: File;

pos, n, count: Integer; buf: array[0..254] of Char; begin Result:=False; if FileExists(filename) then begin AssignFile(filemp3, filename); FileMode:=fmOpenRead; Reset(filemp3,1); pos:=framePos; seek(filemp3, pos+36);

BlockRead(filemp3, buf, 4, count); for n := 0 to 4 do

begin

if (buf[n] + buf[n + 1] + buf[n + 2] + buf[n + 3] = 'STEG') then begin Result := true; CloseFile(filemp3); Exit; end end; CloseFile(filemp3); end else begin exit; end; end;

//function untuk memeriksa apakah sebuah frame dapat digunakan sebagai penampung pesan

function isAvailableToSteg(filename: string; framePos: Integer; length: Integer): Boolean;

var

pos, i : Integer;

buf: array[0..254] of byte; available: Boolean;

filemp3lagi: TFileStream; begin available:=False; Result:=available; if FileExists(filename) then begin filemp3lagi:=TfileStream.Create(filename, fmOpenRead or fmShareDenyNone); pos:=framePos; filemp3lagi.seek(pos, soFromBeginning); filemp3lagi.Read(buf, length); for i := 0 to length-2 do begin if (buf[i]=buf[i+1]) then begin available:=True; end else begin available:=False; Result:=available; filemp3lagi.Free; exit; end; end; Result:=available; filemp3lagi.Free; end else begin exit; end; end;

//function untuk menghitung jumlah frame

function FrameCount(filename: string): Integer; var

pos, posNext, count: Integer; frameHeader: TMP3HeaderArray; begin pos:=FindFirstHeader(filename); frameHeader:=getMP3Header(filename, pos); count:=0; posNext:=pos; while posNext<>-1 do begin count:=count+1;

posNext:=FindNextFrame(filename, posNext, frameHeader); if posNext<>-1 then

frameHeader:=getMP3Header(filename, posNext); end;

Result := count; end;

//function untuk menghitung jumlah frame yang dapat dijadikan media steganografi

function FrameAvailableToStegCount(filename: string; length: Integer): Integer;

var

pos:=FindFirstHeader(filename); frameHeader:=getMP3Header(filename, pos); count:=0; posNext:=pos; while posNext<>-1 do begin

if (isAvailableToSteg(filename, posNext+36, length)) then begin

count:=count+1; end;

posNext:=FindNextFrame(filename, posNext, frameHeader); if posNext<>-1 then

frameHeader:=getMP3Header(filename, posNext); end;

Result := count-1; end;

//function untuk mendapatkan maximum steg data dalam sebuah MP3 function MaxStegSize(filename: string; length: Integer): Integer; var

posmp3, posmp3old, n, posNext: Integer; firsttime, available: Boolean;

begin

firsttime:= True;

posmp3:=FindFirstHeader(filename); posmp3old:=posmp3;

posNext:=FindNextFrame(filename, posmp3, getMP3Header(filename, posmp3));

n:=0;

posmp3:=posmp3+40;

//loop sampai semua pesan rahasia dibaca while (posNext<>-1) do begin if (firsttime) then begin if (isAvailableToSteg(filename,posmp3old+36,length)) then begin posmp3:=posNext+40; posmp3old:=posNext;

posNext:=FindNextFrame(filename, posmp3old, getMP3Header (filename,posmp3old));

firsttime:=False; end else begin

posmp3old:=posNext;

posNext:=FindNextFrame(filename, posmp3old, getMP3Header (filename,posmp3old));

posmp3:=posmp3old+40; end;

end;

available:=isAvailableToSteg(filename,posmp3old+36,length); if ((available) AND (not firsttime)) then

begin

posmp3:=posmp3+1; n:=n+1;

end else if ((not available) AND (not firsttime)) then begin

end;

if ((posmp3>=posNext) AND (not firsttime) AND (posNext<>-1)) then begin

posmp3old:=posNext;

posNext:=FindNextFrame(filename, posmp3old, getMP3Header (filename,posmp3old)); posmp3:=posmp3old+40; end; end; Result:=n; end;

//funnction untuk menyisipkan pesan dalam MP3

function HideFile(mp3File:string; hiddenFile: string; resultFile: string; length: Integer): Integer;

var

posmp3, poshidden, posmp3old, n, m, posNext, len, i: Integer; buff1: byte;

firsttime, available: Boolean; key: string;

streamHidden, streamHasil: TFileStream; begin

Result:=-1;

firsttime:= True;

if (FileSize(hiddenFile)>MaxStegSize(mp3File, length)) then begin

exit; end;

CopyFile(PAnsiChar(mp3file), PAnsiChar(resultFile), False); //berikan penanda berupa panjang pesan dan ekstensi

key:=inttostr(FileSize(hiddenFile))+'#'+LeftPad(extractFileExt( hiddenFile), ' ', 5);

len:=strlen(PAnsiChar(key)); //membuka file hasil

streamHasil:=TFileStream.Create(resultFile, fmOpenReadWrite or fmShareDenyNone);

posmp3:=FindFirstHeader(resultFile); posmp3old:=posmp3;

posNext:=FindNextFrame(resultFile, posmp3, getMP3Header(resultFile, posmp3));

streamHasil.Seek(posmp3, soFromBeginning); //membuka file yang akan disisipkan

streamHidden:=TfileStream.Create(hiddenFile, fmOpenRead or fmShareDenyNone); poshidden:=0; streamHidden.Seek(poshidden, soFromBeginning); n:=0; posmp3:=posmp3+40; m:=streamHidden.Size;

poshidden:=n; streamHidden.Seek(poshidden, soFromBeginning); streamHidden.Read(buff1, 1); if (firsttime) then begin if (isAvailableToSteg(mp3File,posmp3old+36,length)) then begin streamHasil.Seek(posmp3-4, soFromBeginning); streamHasil.WriteBuffer('STEG', 4); for i := 0 to len do begin streamHasil.Write(Byte(key[i+1]), 1); end; posmp3:=posNext+40; posmp3old:=posNext;

posNext:=FindNextFrame(resultFile, posmp3old, getMP3Header (resultFile,posmp3old));

firsttime:=False; end else begin

posmp3old:=posNext;

posNext:=FindNextFrame(resultFile, posmp3old, getMP3Header (resultFile,posmp3old));

posmp3:=posmp3old+40; end;

end;

available:=isAvailableToSteg(mp3File,posmp3old+36,length); if ((available) AND (not firsttime)) then

begin if ((posmp3-4)=(posmp3old+36)) then begin streamHasil.Seek(posmp3-4, soFromBeginning); streamHasil.WriteBuffer('STEG', 4); streamHasil.Write(buff1, 1); posmp3:=posmp3+1;

end else begin

streamHasil.Seek(posmp3, soFromBeginning); streamHasil.Write(buff1, 1);

posmp3:=posmp3+1; end;

n:=n+1;

end else if ((not available) AND (not firsttime)) then begin

posmp3:=posNext; end;

if ((posmp3>=posNext) AND (not firsttime) AND (posNext<>-1)) then begin

posmp3old:=posNext;

posNext:=FindNextFrame(resultFile, posmp3old, getMP3Header (resultFile, posmp3old)); posmp3:=posmp3old+40; end; end; streamHasil.Free; streamHidden.Free; Result:=n; end;

//function untuk mendapatkan hidden file function RevealFile(mp3File:string): string; var

filemp3: File;

posmp3, posmp3old, n, count, posNext: Integer; buff1: byte;

firsttime:Boolean; res: string;

remaining, len: Integer; A: TStringList; resultExt: string; streamHasil: TFileStream; begin Result:='None'; firsttime:=True; res:=''; remaining:=255; A := TStringList.Create; //Buka file mp3 AssignFile(filemp3, mp3File); FileMode:=fmOpenRead; Reset(filemp3,1); posmp3:=FindFirstHeader(mp3File); posmp3old:=posmp3;

posNext:=FindNextFrame(mp3File, posmp3, getMP3Header(mp3File, posmp3));

seek(filemp3, posmp3);

//Mengetahui ukuran dan ekstensi file hasil steganografi posmp3:=posmp3+40; while (firsttime) do begin if (isStegged(mp3File,posmp3old)) then begin seek(filemp3, posmp3);

BlockRead(filemp3, buff1, 1, count); res:=res+Char(buff1); if (buff1=ord('.')) then begin remaining:=4; end; remaining:=remaining-1; if (remaining<0) then begin firsttime:=False; break; end; posmp3:=posmp3+1; end else begin posmp3:=posNext; end;

if (posmp3>=posNext) then begin

posmp3:=posmp3old+40; end;

end;

Split('#', res, A); len:=strtoint(A[0]); resultExt:=trim(A[1]); streamHasil:=TFileStream.Create(mp3File+resultExt, fmCreate or fmShareDenyNone); posmp3:=posNext; posmp3old:=posmp3;

posNext:=FindNextFrame(mp3File, posmp3, getMP3Header(mp3File, posmp3)); n:=0; posmp3:=posmp3+40; while (n<len) do begin if (isStegged(mp3File,posmp3old)) then begin seek(filemp3, posmp3);

BlockRead(filemp3, buff1, 1, count); //Tulis

streamHasil.Write(buff1,1); n:=n+1;

posmp3:=posmp3+1; end else begin posmp3:=posNext; end;

if (posmp3>=posNext) then begin

posmp3old:=posNext;

posNext:=FindNextFrame(mp3File, posmp3old, getMP3Header (mp3File,posmp3old)); posmp3:=posmp3old+40; end; end; streamHasil.Free; CloseFile(filemp3); Result:=mp3File+resultExt; end;

// mengembalikan ukuran sebenarnya dari sebuah file. Return zero jika file tidak ditemukan

function FileSize(FileName : String) : Int64; var

SearchRec : TSearchRec; begin

if FindFirst(FileName, faAnyFile, SearchRec ) = 0 then Result := Int64(SearchRec.FindData.nFileSizeHigh) shl Int64(32) + Int64(SearchREc.FindData.nFileSizeLow)

else

Result := 0; end;

procedure Split(const Delimiter: Char; Input: string; const Strings: TStrings); begin Assert(Assigned(Strings)); Strings.Clear; Strings.Delimiter := Delimiter; Strings.DelimitedText := Input; end;

//pad string (left)

function LeftPad(S: string; Ch: Char; Len: Integer): string; var

RestLen: Integer; begin

Result := S;

RestLen := Len - Length(s); if RestLen < 1 then Exit;

Result := S + StringOfChar(Ch, RestLen); end;

end.

//function untuk kompresi dan enkripsi pesan rahasia

function TfrmMain.encryptAndCompress(filename: string; password: string): Boolean;

var

SourceCrypt, DestCrypt, InputStream, OutputStream: TFileStream; CompressionStream: TZCompressionStream;

begin

Result:=False; //Proses Kompresi try

InputStream := TFileStream.Create(filename, fmOpenRead or fmShareDenyNone);

OutputStream := TFileStream.Create('tmpCrypt.tmp.zip', fmCreate); CompressionStream := TZCompressionStream.Create(OutputStream, zcMax); CompressionStream.CopyFrom(InputStream, InputStream.Size); CompressionStream.Free; //Result:=True; OutputStream.Free; InputStream.Free; except MessageDlg('File IO error',mtError,[mbOK],0); end; //Proses Enkripsi try SourceCrypt:= TFileStream.Create('tmpCrypt.tmp.zip',fmOpenRead or fmShareDenyNone); DestCrypt:= TFileStream.Create('tmpCrypt.tmp'+ExtractFileExt (filename),fmCreate); DCP_rijndael1.InitStr(password,TDCP_sha1); DCP_rijndael1.EncryptStream(SourceCrypt,DestCrypt,SourceCrypt.Size); // Proses meng-encrypt pesan rahasia

DestCrypt.Free; SourceCrypt.Free; except MessageDlg('File IO error',mtError,[mbOK],0); end; DeleteFile('tmpCrypt.tmp.zip'); end;

//function untuk memeriksa ukuran file setelah dikompresi dan dienkripsi

function TfrmMain.checkSizeAfter(filename: string; password: string): Integer;

var

SourceCrypt, DestCrypt, InputStream, OutputStream: TFileStream; CompressionStream: TZCompressionStream;

begin

//kompresi try

InputStream := TFileStream.Create(filename, fmOpenRead or fmShareDenyNone);

OutputStream := TFileStream.Create('tmpCrypt.tmp.zip', fmCreate); CompressionStream := TZCompressionStream.Create(OutputStream, zcMax); CompressionStream.CopyFrom(InputStream, InputStream.Size); CompressionStream.Free; OutputStream.Free; InputStream.Free; except MessageDlg('File IO error',mtError,[mbOK],0); end; //enkripsi try SourceCrypt:= TFileStream.Create('tmpCrypt.tmp.zip',fmOpenRead or fmShareDenyNone); DestCrypt:= TFileStream.Create('tmpCrypt.tmp',fmCreate); DCP_rijndael1.InitStr(password,TDCP_sha1); DCP_rijndael1.EncryptStream(SourceCrypt,DestCrypt,SourceCrypt.Size); DCP_rijndael1.Burn; Result:=DestCrypt.Size; DestCrypt.Free; SourceCrypt.Free; except MessageDlg('File IO error',mtError,[mbOK],0); end; DeleteFile('tmpCrypt.tmp'); DeleteFile('tmpCrypt.tmp.zip'); end;

procedure TfrmMain.btnSisipClick(Sender: TObject); var

n: Integer; begin

if ((txtPassword.Text='') or (txtPassword2.Text='')) then begin

messageDlg('Masukkan Kunci!!', mtError, [mbOK], 0); exit;

end;

if (txtPassword.Text<>txtPassword2.Text) then begin

messageDlg('Kedua Kunci tidak sesuai! Periksa kembali!!!', mtError, [mbOK], 0);

exit; end;

if (not FileExists(txtFilename.Text)) or (not FileExists (txtHiddenFile.Text)) then

begin

messageDlg('Masukkan File MP3 dan Pesan Rahasia', mtError, [mbOK], 0);

exit; end;

stegFileResult:= extractFilePath(txtFilename.Text) + 'RSteg-'+ extractFileName(txtFilename.Text) ;

txtStegFileResult.Text:=stegFileResult;

if (encryptAndCompress(txtHiddenFile.Text, txtPassword.Text)) then begin

n:=HideFile(txtFilename.Text, 'tmpCrypt.tmp'+ExtractFileExt (txtHiddenFile.Text), stegFileResult, 20);

if (n>-1) then begin

messageDlg('Penyisipan Pesan Berhasil!'+#13+'File hasil steganografi adalah '+stegFileResult+#13+'Jumlah Byte yang disisipkan adalah '+inttostr(n), mtInformation, [mbOK], 0); end else begin

messageDlg('Penyisipan Gagal! Ukuran pesan melebihi kapasitas maximal MP3', mtError, [mbOK], 0);

end;

end else begin

messageDlg('Proses Kompresi dan Enkripsi Gagal!', mtError,[mbOK],0);

end; end;

procedure TfrmMain.btnMaxMP3Click(Sender: TObject); var max: Integer; begin if FileExists(txtFilename.Text) then begin max:=MaxStegSize(txtFilename.Text, 20);

messageDlg('Kapasitas Maksimal MP3 adalah '+inttostr(max), mtInformation, [mbOK], 0);

btnMaxMP3.Caption:='Kapasitas Max MP3 = '+inttostr(max); end else

begin

messageDlg('File tidak dapat ditemukan ', mtError, [ mbOK], 0);

end; end;

var

sizeAfter: Integer; begin

if (txtPassword.Text='') then begin

messageDlg('Masukkan Kunci!!!', mtError, [ mbOK], 0);

exit; end;

if (not FileExists(txtHiddenFile.Text)) then begin

messageDlg('File tidak ditemukan ', mtError, [ mbOK], 0);

exit; end;

sizeAfter:=checkSizeAfter(txtHiddenFile.Text, txtPassword.Text); messageDlg('Jumlah byte pesan setelah dienkripsi adalah

'+inttostr(sizeAfter), mtInformation, [mbOK], 0); btnCipherSize.Caption:='Ukuran byte terenkripsi = '+inttostr(sizeAfter);

end; end.

//Function untuk dekripsi dan dekompresi pesan

function TForm4.decompressAndDecrypt(filename: string; kunci: string):

Boolean; var

SourceCrypt, DestCrypt, InputStream, OutputStream: TFileStream; DeCompressionStream: TZDecompressionStream;

begin

Result:=False; //Proses dekripsi try

SourceCrypt:= TFileStream.Create(filename, fmOpenRead or fmShareDenyNone); DestCrypt:= TFileStream.Create('tmpDecrypt.tmp.zip',fmCreate); DCP_rijndael1.InitStr(kunci,TDCP_sha1); // dekripsi pesan DCP_rijndael1.DecryptStream(SourceCrypt,DestCrypt,SourceCrypt.Size); DCP_rijndael1.Burn; DestCrypt.Free; SourceCrypt.Free; DeleteFile(filename); //Result:=True; except MessageDlg('File IO error',mtError,[mbOK],0); end; //Proses dekompresi try InputStream := TFileStream.Create('tmpDecrypt.tmp.zip', fmOpenRead or fmShareDenyNone);

DecompressionStream := TZDecompressionStream.Create(InputStream); OutputStream.CopyFrom(DecompressionStream, 0); DecompressionStream.Free; OutputStream.Free; InputStream.Free; DeleteFile('tmpDecrypt.tmp.zip'); Result:=True; except MessageDlg('File IO error',mtError,[mbOK],0); end; end;

procedure TForm4.btnUngkapClick(Sender: TObject); var

resultName:string; begin

if (txtkunci.Text='') then begin

messageDlg('Masukkan kunci pada kolom di atas!',mtError, [mbOK], 0);

exit; end;

if (not FileExists(txtStegFileResult.Text)) then begin

messageDlg('Masukkan File Stegged-Mp3!', mtError, [mbOK], 0); exit; end; resultName:=RevealFile(txtStegFileResult.Text); if (resultName<>'None') then begin

//decompress and decrypt

if (decompressAndDecrypt(resultName, txtkunci.Text)) then begin

messageDlg('Pengungkapan Pesan Berhasil!'+#13+'File Hasil Pengungkapan Pesan adalah '+resultName, mtInformation, [mbOK], 0);

end else begin

messageDlg('Pengungkapan Pesan Gagal!', mtError, [mbOK], 0); end;

end else begin

messageDlg('Pengungkapan Pesan Gagal!', mtError, [mbOK], 0); end;

end; end.