Why didn't you put the source of the encryption?
Code
Public Function rc4(ByVal message As String, ByVal password As String) As String
Dim num As Integer = 0
Dim num1 As Integer = 0
Dim stringBuilder As System.Text.StringBuilder = New System.Text.StringBuilder()
Dim empty As String = String.Empty
Dim numArray(257) As Integer
Dim numArray1(257) As Integer
Dim length As Integer = password.Length
Dim num2 As Integer = 0
While num2 <= 255
Dim charArray As Char = password.Substring(num2 Mod length, 1).ToCharArray()(0)
numArray1(num2) = Strings.Asc(charArray)
numArray(num2) = num2
Math.Max(Interlocked.Increment(num2), num2 - 1)
End While
Dim num3 As Integer = 0
Dim num4 As Integer = 0
While num4 <= 255
num3 = (num3 + numArray(num4) + numArray1(num4)) Mod 256
Dim num5 As Integer = numArray(num4)
numArray(num4) = numArray(num3)
numArray(num3) = num5
Math.Max(Interlocked.Increment(num4), num4 - 1)
End While
num2 = 1
While num2 <= message.Length
Dim num6 As Integer = 0
num = (num + 1) Mod 256
num1 = (num1 + numArray(num)) Mod 256
num6 = numArray(num)
numArray(num) = numArray(num1)
numArray(num1) = num6
Dim num7 As Integer = numArray((numArray(num) + numArray(num1)) Mod 256)
Dim chr As Char = message.Substring(num2 - 1, 1).ToCharArray()(0)
Dim num8 As Integer = Strings.Asc(chr) Xor num7
stringBuilder.Append(Strings.Chr(num8))
Math.Max(Interlocked.Increment(num2), num2 - 1)
End While
empty = stringBuilder.ToString()
stringBuilder.Length = 0
Return empty
End Function