Algoritma Blowfish adalah salah satu algoritma yang dapat digunakan untuk melakukan enkripsi data sehingga data asli hanya dapat dibaca oleh seseorang yang memiliki kunci enkripsi tersebut. Contoh yang dibahas kali ini adalah mengenai enkripsi dan dekripsi dari sebuah kalimat.
Algoritma ini menggunakan teknik cipher blok dengan key simetris. Blowfish memiliki ukuran blok 64 bit dan panjang key dari 32 sampai 448 bit. Blowfish menggunakan cipher Feistel dan menggunakan parameter SBOX yang sangat besar dan nilainya bergantung dari key. Strukturnya sangat mirip dengan struktur CAST-128, yang menggunakan SBOX dengan nilai tetap.
Langkah-langkah penggunaan algoritma ini adalah
1. Tentukan kalimat yang akan dienkrip
Console.WriteLine("Masukkan kalimat yang akan dienkrip: ")
Dim input As String = Console.ReadLine
2. Tentukan kata kunci enkripsi yang digunakan
Console.WriteLine("Masukkan kata kunci enkripsi: ")
Dim kataKunci As String = Console.ReadLine
3. Lakukan inisialisasi variabel yang digunakan oleh metode ini
Penjelasan lebih detail tentang fungsi ini dapat dilihat pada penjelasan skrip dibawah ini
Dim xc As New CryptCore() xc.InitCore() xc.Key = kataKunci
* Skrip tersebut akan melakukan inisialisasi pada Class CryptCore. Class ini adalah inti class untuk pemanggilan fungsi enkripsi dan dekripsi yang mengacu pada algoritma blowfish. Deklarasi Class CryptCore adalah sebagai berikut:
Public Class CryptCore
Private _key As String = Nothing
Public Property Key() As String
Get
Return _key
End Get
Set(value As String)
_key = Me.formatKey(value)
End Set
End Property
Private Function formatKey(key As String) As String
If key Is Nothing OrElse key.Length = 0 Then
Return Nothing
End If
Return key.Trim()
End Function
Private DefaultKey As String = ""
Public Sub New()
DefaultKey = "enkripsi"
End Sub
Private _coreSymmetric As CoreAlgoritmaSymmetric
Public Function InitCore() As Boolean
_coreSymmetric = New CoreAlgoritmaSymmetric()
Return True
End Function
. . .
End Class
* Pada saat melakukan proses InitCore, maka proses tersebut akan melakukan inisialisasi pada Class CoreAlgoritmaSymmetric. Pemanggilan fungsi enkripsi / dekripsi pada Class sebelumnya akan mengarah pada Class ini untuk selanjutnya dilakukan perhitungan enkripsi / dekripsi yang sebenarnya. Deklarasi Class CoreAlgoritmaSymmetric adalah sebagai berikut:
Public Class CoreAlgoritmaSymmetric Private metodeEncode As System.Security.Cryptography.SymmetricAlgorithm Public Sub New() metodeEncode = New BlowfishAlgoritma() metodeEncode.Mode = System.Security.Cryptography.CipherMode.CBC metodeEncode.KeySize = 40 metodeEncode.GenerateKey() metodeEncode.GenerateIV() End Sub . . . End Class
* Pada saat menginisialisasi variabel metodeEncode, maka proses tersebut akan melakukan inisialisasi pada Class BlowfishAlgoritma. Class ini berisi tentang beberapa properti dan fungsi yang menggantikan properti dan fungsi yang diturunkan dari Class SymmetricAlgorithm dan ICryptoTransform. Deklarasi Class BlowfishAlgoritma adalah sebagai berikut:
Public Class BlowfishAlgoritma
Inherits System.Security.Cryptography.SymmetricAlgorithm
Implements System.Security.Cryptography.ICryptoTransform
Private m_bf As Blowfish
Private m_bfcbc As BlowfishBaseCBC
Private m_blIsEncryptor As Boolean
Private m_rng As System.Security.Cryptography.RNGCryptoServiceProvider
Public Sub New()
MyBase.New()
m_bf = Nothing
m_bfcbc = Nothing
IVValue = Nothing
KeyValue = Nothing
KeySizeValue = Blowfish.MaksPanjangKey * 8
LegalBlockSizesValue = New System.Security.Cryptography.KeySizes(0) {}
LegalBlockSizesValue(0) = New System.Security.Cryptography.KeySizes(BlockSize, BlockSize, 8)
LegalKeySizesValue = New System.Security.Cryptography.KeySizes(0) {}
LegalKeySizesValue(0) = New System.Security.Cryptography.KeySizes(0, Blowfish.MaksPanjangKey * 8, 8)
ModeValue = System.Security.Cryptography.CipherMode.ECB
m_rng = Nothing
End Sub
. . .
End Class
4. Lakukan enkripsi kalimat awal menggunakan algoritma ini
Penjelasan lebih detail tentang fungsi ini dapat dilihat pada penjelasan skrip dibawah ini
Dim hasilEnkripsi As String = xc.Encrypt(input)
* Skrip tersebut akan menjalankan proses enkripsi yang terdapat dalam Class CoreAlgoritmaSymmetric.
Public Function ProsesEncrypt(Source As String, Key As String) As String
If Source Is Nothing OrElse Key Is Nothing OrElse Source.Length = 0 OrElse Key.Length = 0 Then
Return Nothing
End If
If metodeEncode Is Nothing Then
Return Nothing
End If
Dim lPanjangStream As Long
Dim jumlahBufferTerbaca As Integer
Dim byteBuffer As Byte() = New Byte(2) {}
Dim srcData As Byte() = System.Text.ASCIIEncoding.ASCII.GetBytes(Source)
Dim encData As Byte()
Dim streamInput As New System.IO.MemoryStream()
streamInput.Write(srcData, 0, srcData.Length)
streamInput.Position = 0
Dim streamOutput As New System.IO.MemoryStream()
Dim streamEncrypt As System.Security.Cryptography.CryptoStream
metodeEncode.Key = GetValidKey(Key)
metodeEncode.IV = GetValidIV(Key, metodeEncode.IV.Length)
streamEncrypt = New System.Security.Cryptography.CryptoStream(streamOutput, metodeEncode.CreateEncryptor(), System.Security.Cryptography.CryptoStreamMode.Write)
lPanjangStream = streamInput.Length
Dim totalBufferTerbaca As Integer = 0
While totalBufferTerbaca < lPanjangStream
jumlahBufferTerbaca = streamInput.Read(byteBuffer, 0, byteBuffer.Length)
streamEncrypt.Write(byteBuffer, 0, jumlahBufferTerbaca)
totalBufferTerbaca += jumlahBufferTerbaca
End While
streamEncrypt.Close()
encData = streamOutput.ToArray()
'Konversi menjadi base64 agar hasil dapat digunakan dalam xml
Return Convert.ToBase64String(encData)
End Function
* Sedangkan proses enkripsi utama algoritma Blowfish adalah sebagai berikut
Protected Sub BaseEncrypt(ByRef unHiRef As UInteger, ByRef unLoRef As UInteger) Dim unHi As UInteger = unHiRef Dim unLo As UInteger = unLoRef Dim sbox1 As UInteger() = m_sbox1 Dim sbox2 As UInteger() = m_sbox2 Dim sbox3 As UInteger() = m_sbox3 Dim sbox4 As UInteger() = m_sbox4 Dim pbox As UInteger() = m_pbox unHi = unHi Xor pbox(0) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(1) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(2) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(3) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(4) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(5) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(6) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(7) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(8) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(9) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(10) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(11) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(12) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(13) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(14) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(15) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(16) unLoRef = unHi unHiRef = unLo Xor pbox(17) End Sub
5. Lakukan dekripsi dari kalimat yang telah terenkripsi
Penjelasan lebih detail tentang fungsi ini dapat dilihat pada penjelasan skrip dibawah ini
Dim hasilDekripsi As String = xc.Decrypt(hasilEnkripsi)
* Skrip tersebut akan menjalankan proses dekripsi yang terdapat dalam Class CoreAlgoritmaSymmetric.
Public Function ProsesDecrypt(Source As String, Key As String) As String
If Source Is Nothing OrElse Key Is Nothing OrElse Source.Length = 0 OrElse Key.Length = 0 Then
Return Nothing
End If
If metodeEncode Is Nothing Then
Return Nothing
End If
Dim lPanjangStream As Long
Dim jumlahBufferTerbaca As Integer
Dim byteBuffer As Byte() = New Byte(2) {}
Dim encData As Byte() = Convert.FromBase64String(Source)
Dim decData As Byte()
Dim streamInput As New System.IO.MemoryStream(encData)
Dim streamOutput As New System.IO.MemoryStream()
Dim streamDecrypt As System.Security.Cryptography.CryptoStream
metodeEncode.Key = GetValidKey(Key)
metodeEncode.IV = GetValidIV(Key, metodeEncode.IV.Length)
streamDecrypt = New System.Security.Cryptography.CryptoStream(streamInput, metodeEncode.CreateDecryptor(), System.Security.Cryptography.CryptoStreamMode.Read)
lPanjangStream = streamInput.Length
Dim totalBufferTerbaca As Integer = 0
While totalBufferTerbaca < lPanjangStream
jumlahBufferTerbaca = streamDecrypt.Read(byteBuffer, 0, byteBuffer.Length)
If 0 = jumlahBufferTerbaca Then
Exit While
End If
streamOutput.Write(byteBuffer, 0, jumlahBufferTerbaca)
totalBufferTerbaca += jumlahBufferTerbaca
End While
streamDecrypt.Close()
decData = streamOutput.ToArray()
For i As Integer = 0 To decData.Length - 1
If decData(i) < 8 Then decData(i) = 0
Next
Dim encodeASCII As New System.Text.ASCIIEncoding()
Return encodeASCII.GetString(decData)
End Function
* Sedangkan proses dekripsi utama algoritma Blowfish adalah sebagai berikut
Public Overridable Sub Decrypt(ByRef unHiRef As UInteger, ByRef unLoRef As UInteger) Dim unHi As UInteger = unHiRef Dim unLo As UInteger = unLoRef Dim sbox1 As UInteger() = m_sbox1 Dim sbox2 As UInteger() = m_sbox2 Dim sbox3 As UInteger() = m_sbox3 Dim sbox4 As UInteger() = m_sbox4 Dim pbox As UInteger() = m_pbox unHi = unHi Xor pbox(CInt(17)) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(16) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(15) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(14) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(13) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(12) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(11) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(10) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(9) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(8) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(7) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(6) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(5) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(4) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(3) unLo = unLo Xor (((sbox1(CInt(unHi >> 24)) + sbox2(CInt((unHi >> 16) And &HFF))) Xor sbox3(CInt((unHi >> 8) And &HFF))) + sbox4(CInt(unHi And &HFF))) Xor pbox(2) unHi = unHi Xor (((sbox1(CInt(unLo >> 24)) + sbox2(CInt((unLo >> 16) And &HFF))) Xor sbox3(CInt((unLo >> 8) And &HFF))) + sbox4(CInt(unLo And &HFF))) Xor pbox(1) unLoRef = unHi unHiRef = unLo Xor pbox(0) End Sub
* Secara keseluruhan, skrip ini membutuhkan 2 Class tambahan yaitu Class Blowfish dan Class BlowfishBaseCBC. Class Blowfish berisi tentang ukuran blok, panjang key, semua nilai PBOX dan SBOX, dan beberapa fungsi enkripsi dan dekripsi dengan metode Blowfish. Class BlowfishBaseCBC adalah inti class Blowfish yang menggunakan teknik cipher CBC (Cipher Block Chaining), dan berisi tentang beberapa properti dan fungsi yang menggantikan properti dan fungsi yang diturunkan dari Class Blowfish dan SymmetricAlgorithm. Deklarasi kedua Class tersebut adalah sebagai berikut:
Public Class Blowfish
'Panjang maksimal ukuran key dalam byte
Public Const MaksPanjangKey As Integer = 56
'Panjang ukuran blok dalam byte
'Perlu diingat bahwa ukuran data harus menyesuaikan ukuran blok
Public Const ukuranBlok As Integer = 8
Const jumlahInputPBOX As Integer = 18
Const jumlahInputSBOX As Integer = 256
Private m_pbox As UInteger()
Private m_sbox1 As UInteger()
Private m_sbox2 As UInteger()
Private m_sbox3 As UInteger()
Private m_sbox4 As UInteger()
. . .
Public Sub New(key As Byte())
Dim nI As Integer
m_pbox = New UInteger(jumlahInputPBOX - 1) {}
For nI = 0 To jumlahInputPBOX - 1
m_pbox(nI) = InitPBOX(nI)
Next
m_sbox1 = New UInteger(jumlahInputSBOX - 1) {}
m_sbox2 = New UInteger(jumlahInputSBOX - 1) {}
m_sbox3 = New UInteger(jumlahInputSBOX - 1) {}
m_sbox4 = New UInteger(jumlahInputSBOX - 1) {}
For nI = 0 To jumlahInputSBOX - 1
m_sbox1(nI) = InitSBOX1(nI)
m_sbox2(nI) = InitSBOX2(nI)
m_sbox3(nI) = InitSBOX3(nI)
m_sbox4(nI) = InitSBOX4(nI)
Next
'Lakukan operasi XOR key pada semua pbox
Dim panjangKey As Integer = key.Length
If panjangKey = 0 Then Return
Dim posisiKey As Integer = 0
Dim unBuild As UInteger = 0
For nI = 0 To jumlahInputPBOX - 1
For nJ As Integer = 0 To 3
unBuild = (unBuild << 8) Or key(posisiKey)
If System.Threading.Interlocked.Increment(posisiKey) = panjangKey Then
posisiKey = 0
End If
Next
m_pbox(nI) = m_pbox(nI) Xor unBuild
Next
'Lakukan enkripsi pada semua box dengan semua string 0
Dim unZeroHi As UInteger = 0
Dim unZeroLo As UInteger = 0
For nI = 0 To jumlahInputPBOX - 1 Step 2
BaseEncrypt(unZeroHi, unZeroLo)
m_pbox(nI) = unZeroHi
m_pbox(nI + 1) = unZeroLo
Next
For nI = 0 To jumlahInputSBOX - 1 Step 2
BaseEncrypt(unZeroHi, unZeroLo)
m_sbox1(nI) = unZeroHi
m_sbox1(nI + 1) = unZeroLo
Next
For nI = 0 To jumlahInputSBOX - 1 Step 2
BaseEncrypt(unZeroHi, unZeroLo)
m_sbox2(nI) = unZeroHi
m_sbox2(nI + 1) = unZeroLo
Next
For nI = 0 To jumlahInputSBOX - 1 Step 2
BaseEncrypt(unZeroHi, unZeroLo)
m_sbox3(nI) = unZeroHi
m_sbox3(nI + 1) = unZeroLo
Next
For nI = 0 To jumlahInputSBOX - 1 Step 2
BaseEncrypt(unZeroHi, unZeroLo)
m_sbox4(nI) = unZeroHi
m_sbox4(nI + 1) = unZeroLo
Next
End Sub
. . .
End Class
Public Class BlowfishBaseCBC
Inherits Blowfish
Private m_unIvHi As UInteger
Private m_unIvLo As UInteger
Public Sub New(key As Byte(), iv As Byte())
MyBase.New(key)
Me.Iv = iv
End Sub
. . .
Hasil akhir adalah: (klik untuk perbesar gambar)
Contoh modul / source code dalam bahasa VB (Visual Basic) dapat didownload disini:
[sdm_download id="2851" fancy="0"]
Jika membutuhkan jasa kami dalam pembuatan program, keterangan selanjutnya dapat dilihat di Fasilitas dan Harga
Jika ada yang kurang paham dengan langkah-langkah algoritma diatas, silahkan berikan komentar Anda.
Selamat mencoba.
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