Algoritma Blowfish 13

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:

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.