RSA kurucularindan Ronald Rivest tarafindan 1987 yilinda gelistirilmistir. Bu algoritmanin kaynak kodlari 1994 yilinda mechul yollar ve kisiler tarafindan internet ortaminda yayinlanmistir. RC4 belirlenen anahtar ile veriyi sifreleyen bir algoritmadir. Kendi kendine senkronize eden algoritmalar katagorisinde yer almaktadir.

• RC4 algoritmasi sifrelenecek veriyi akan bir bit dizisi olarak

algilar.RC4 belirlenen anahtar ile veriyi sifreleyen bir algoritmadir.

RC4′ü basia öellikleri snlardi:

•Genellikle hiz gerektiren uygulamalarda kullanilir.

•Sfreleme hizi yüksektir ve MB/sn seviyesindedir.

•Güvenligi rastgele bir anahtar kullanimina bagidir.

•Tekrarlama periyodu 10100′den daha fazladi.

•Kötü anahtari bulunmamaktadir.

•Anahtar uzunlugu degisendir.

VB.NET PolyRC4 Class dosyasi kodlari;

Imports System.Text

Public Class PolyRC4

Private Key As String = "923- i231id3id12di12 mod1o2do12d*DU221-u(@10ie02i0=di=@)!IE)I@Do12\doqwo["

Sub New(ByVal EncryptionKey As String)

Key = EncryptionKey

End Sub

Public Function Encrypt(ByVal message As String) As String

message = x(message, Key)

Dim random As New Random()

Dim list1 As New ArrayList(), list2 As New ArrayList()

Dim out As String = ""

Dim num1 As Integer = random.[Next](1, 10255)

For i As Integer = 0 To message.Length - 1

Dim num2 As Integer = random.[Next](num1)

list1.Add(Convert.ToInt32(message(i)) + num2)

list2.Add(num2)

Next

For j As Integer = 0 To message.Length - 1

out += ChrW(list1(j)) & ChrW(list2(j))

Next

Return out

End Function

Public Function Decrypt(ByVal message As String) As String

Dim numArray As Integer() = New Integer(message.Length - 1) {}

Dim temp As String = ""

For i As Integer = 0 To message.Length - 1

numArray(i) = Convert.ToInt32(message(i))

Next

For j As Integer = 0 To message.Length - 1 Step 2

Dim num3 As Integer = numArray(j)

Dim num4 As Integer = numArray(j + 1)

Dim num5 As Integer = num3 - num4

temp = temp + ChrW(num5)

Next

Return x(temp, Key)

End Function

Private Function x(ByVal nGeeKnK As String, ByVal eKieBrN As String) As String

Dim oHgeIrT As Integer = 0

Dim rErnEoE As Integer = 0

Dim rEeiRfF As New StringBuilder

Dim nJrnJgL As String = String.Empty

Dim bIjeGnR As Integer() = New Integer(256) {}

Dim nBjvRbE As Integer() = New Integer(256) {}

Dim gEgeGnE As Integer = eKieBrN.Length

Dim fBjeEgE As Integer = 0

While fBjeEgE <= 255

Dim fGrjEnG As Char = (eKieBrN.Substring((fBjeEgE Mod gEgeGnE), 1).ToCharArray()(0))

nBjvRbE(fBjeEgE) = Microsoft.VisualBasic.Strings.Asc(fGrjEnG)

bIjeGnR(fBjeEgE) = fBjeEgE

System.Math.Max(System.Threading.Interlocked.Increment(fBjeEgE), fBjeEgE - 1)

End While

Dim vHbrDnG As Integer = 0

Dim jPkkXjV As Integer = 0

While jPkkXjV <= 255

vHbrDnG = (vHbrDnG + bIjeGnR(jPkkXjV) + nBjvRbE(jPkkXjV)) Mod 256

Dim nCokVrH As Integer = bIjeGnR(jPkkXjV)

bIjeGnR(jPkkXjV) = bIjeGnR(vHbrDnG)

bIjeGnR(vHbrDnG) = nCokVrH

System.Math.Max(System.Threading.Interlocked.Increment(jPkkXjV), jPkkXjV - 1)

End While

fBjeEgE = 1

While fBjeEgE <= nGeeKnK.Length

Dim rErrTnE As Integer = 0

oHgeIrT = (oHgeIrT + 1) Mod 256

rErnEoE = (rErnEoE + bIjeGnR(oHgeIrT)) Mod 256

rErrTnE = bIjeGnR(oHgeIrT)

bIjeGnR(oHgeIrT) = bIjeGnR(rErnEoE)

bIjeGnR(rErnEoE) = rErrTnE

Dim rHgeHgH As Integer = bIjeGnR((bIjeGnR(oHgeIrT) + bIjeGnR(rErnEoE)) Mod 256)

Dim fGrjEnG As Char = nGeeKnK.Substring(fBjeEgE - 1, 1).ToCharArray()(0)

rErrTnE = Asc(fGrjEnG)

Dim vRbTKeR As Integer = rErrTnE Xor rHgeHgH

rEeiRfF.Append(Chr(vRbTKeR))

System.Math.Max(System.Threading.Interlocked.Increment(fBjeEgE), fBjeEgE - 1)

End While

nJrnJgL = rEeiRfF.ToString

rEeiRfF.Length = 0

Return nJrnJgL

End Function

End Class

Nasil kullanilir ?

Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click

Dim x As New PolyRC4("1568798iohnfg167dfdf")

txtResult.Text = x.Encrypt(txtinput.Text)

End Sub