Cryptage / decryptage rc4 pour vb .net

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Hello,

J'ai porté en VB .Net la classe de cryptage RC4 de lolo32. J'y ai ajouté quelques fonctionnalités en plus :

-cryptage d'un fichier dans un variable
- cryptage d'un fichier dans un autre fichier

- décryptage d'un fichier dans une variable
- décryptage d'un fichier dans un autre fichier

- génération aléatoire d'une clef de cryptage

Source / Exemple : 


Option Explicit On 

Imports System.IO
Imports System.Text

Public Class RC4
    '/*******************************************/
    '/* Mise à jour v_1.0.1

    'Classe de cryptage réécrite pour VB .NET à partir du code de 
    'lolo32 (http://www.vbfrance.com/article.aspx?Val=5278)
    ' Pour toute question dcampillo@gmail.com

#Region "Const"
    Private _version As String = "1.0.1"
#End Region

#Region "Private var"
    Private S(255) As Integer
    Private cls_Key As String
#End Region

#Region "Property"
    Public Property Key() As String
        Get
            Return cls_Key
        End Get
        Set(ByVal Key As String)
            cls_Key = Key
        End Set
    End Property

    Public ReadOnly Property Version() As String
        Get
            Return _version
        End Get
    End Property
#End Region

    Public Sub New()

    End Sub

    Public Sub New(ByVal Key As String)
        Me.Key = Key
    End Sub

    Public Function Crypt(ByVal Param As String) As String
        Dim ParamLen As Integer = Param.Length
        Dim C As Integer
        Dim T As Integer
        Dim i As Integer
        Dim j As Integer

        Dim oStringBuilder As New StringBuilder

        CreateKeyArray()

        For C = 0 To ParamLen - 1
            i = (i + 1) And 255
            j = (j + S(i)) And 255
            T = S(i)
            S(i) = S(j)
            S(j) = T

            T = (S(i) + S(j)) And 255

            oStringBuilder.Append(Chr(Asc(Param.Substring(C, 1)) Xor S(T)))
        Next C

        Return oStringBuilder.ToString
    End Function

    Public Overloads Function CryptFile(ByVal FilePath As String) As String
        Dim oFileInfo As New FileInfo(FilePath)

        If oFileInfo.Exists Then
            Dim oFileStream As New FileStream(FilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)
            Dim oFileReader As New StreamReader(oFileStream, System.Text.Encoding.Default)

            If oFileStream.CanRead Then
                Dim FileContent As String = oFileReader.ReadToEnd
                Dim FileLen As Int32 = FileContent.Length
                Dim C As Integer
                Dim T As Integer
                Dim i As Integer
                Dim j As Integer

                Dim oStringBuilder As New StringBuilder

                CreateKeyArray()

                For C = 0 To FileLen - 1
                    i = (i + 1) And 255
                    j = (j + S(i)) And 255
                    T = S(i)
                    S(i) = S(j)
                    S(j) = T

                    T = (S(i) + S(j)) And 255

                    oStringBuilder.Append(Chr(Asc(FileContent.Substring(C, 1)) Xor S(T)))
                Next C

                Return oStringBuilder.ToString
            Else
                Throw New Exception("Impossible de lire le fichier " & FilePath)

            End If
        Else
            Throw New Exception("Impossible de trouver le fichier " & FilePath)
        End If
    End Function

    Public Overloads Function CryptFile(ByVal FilePath As String, ByVal OutPutFile As String) As Long
        Dim oFileInfo As New FileInfo(FilePath)

        If oFileInfo.Exists Then
            Dim oFileStream As New FileStream(FilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)
            Dim oFileReader As New StreamReader(oFileStream, System.Text.Encoding.Default)

            If oFileStream.CanRead Then
                Dim FileContent As String = oFileReader.ReadToEnd
                oFileStream.Close()
                oFileReader.Close()

                Dim ParamLen As Int32 = FileContent.Length
                Dim C As Integer
                Dim T As Integer
                Dim i As Integer
                Dim j As Integer

                Dim oStringBuilder As New StringBuilder

                CreateKeyArray()

                For C = 0 To ParamLen - 1
                    i = (i + 1) And 255
                    j = (j + S(i)) And 255
                    T = S(i)
                    S(i) = S(j)
                    S(j) = T

                    T = (S(i) + S(j)) And 255

                    oStringBuilder.Append(Chr(Asc(FileContent.Substring(C, 1)) Xor S(T)))
                Next C

                Dim oWriteStream As New FileStream(OutPutFile, FileMode.Create, FileAccess.Write, FileShare.ReadWrite)
                Dim oFileWriter As New StreamWriter(oWriteStream, System.Text.Encoding.Default)

                Try
                    oFileWriter.Write(oStringBuilder.ToString)
                Catch err As Exception
                    Throw New Exception("Impossible d'écrire le fichier de sortie " & OutPutFile)
                End Try

                oFileWriter.Close()

                Return 0

            Else
                Throw New Exception("Impossible de lire le fichier " & FilePath)
            End If
        Else
            Throw New Exception("Impossible de trouver le fichier " & FilePath)
        End If
    End Function

    Public Function Decrypt(ByVal Param As String) As String

        Dim ParamLen As Integer = Len(Param)
        Dim C As Integer
        Dim T As Integer
        Dim i As Integer
        Dim j As Integer

        Dim oStringBuilder As New StringBuilder

        CreateKeyArray()

        For C = 0 To ParamLen - 1
            i = (i + 1) And 255
            j = (j + S(i)) And 255
            T = S(i)
            S(i) = S(j)
            S(j) = T

            T = (S(i) + S(j)) And 255

            oStringBuilder.Append(Chr(Asc(Param.Substring(C, 1)) Xor S(T)))
        Next C
        Return oStringBuilder.ToString
    End Function

    Public Overloads Function DecryptFile(ByVal FilePath As String) As String

        Dim oFileInfo As New FileInfo(FilePath)

        If oFileInfo.Exists Then
            Dim oFileStream As New FileStream(FilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)
            Dim oFileReader As New StreamReader(oFileStream, System.Text.Encoding.Default)

            If oFileStream.CanRead Then
                Dim FileContent As String = oFileReader.ReadToEnd
                Dim FileLen As Int32 = FileContent.Length
                Dim C As Integer
                Dim T As Integer
                Dim i As Integer
                Dim j As Integer

                Dim oStringBuilder As New StringBuilder

                CreateKeyArray()

                For C = 0 To FileLen - 1
                    i = (i + 1) And 255
                    j = (j + S(i)) And 255
                    T = S(i)
                    S(i) = S(j)
                    S(j) = T

                    T = (S(i) + S(j)) And 255

                    oStringBuilder.Append(Chr(Asc(FileContent.Substring(C, 1)) Xor S(T)))
                Next C
                Return oStringBuilder.ToString
            Else
                Throw New Exception("Impossible de lire le fichier " & FilePath)
            End If
        Else
            Throw New Exception("Impossible de trouver le fichier " & FilePath)
        End If
    End Function

    Public Overloads Function DecryptFile(ByVal FilePath As String, ByVal OutPutFile As String) As Long

        Dim oFileInfo As New FileInfo(FilePath)

        If oFileInfo.Exists Then
            Dim oFileStream As New FileStream(FilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)
            Dim oFileReader As New StreamReader(oFileStream, System.Text.Encoding.Default)

            If oFileStream.CanRead Then
                Dim FileContent As String = oFileReader.ReadToEnd
                Dim FileLen As Int32 = FileContent.Length
                Dim C As Integer
                Dim T As Integer
                Dim i As Integer
                Dim j As Integer

                Dim oStringBuilder As New StringBuilder

                CreateKeyArray()

                For C = 0 To FileLen - 1
                    i = (i + 1) And 255
                    j = (j + S(i)) And 255
                    T = S(i)
                    S(i) = S(j)
                    S(j) = T

                    T = (S(i) + S(j)) And 255

                    oStringBuilder.Append(Chr(Asc(FileContent.Substring(C, 1)) Xor S(T)))
                Next C

                Dim oWriteStream As New FileStream(OutPutFile, FileMode.Create, FileAccess.Write, FileShare.None)
                Dim oFileWriter As New StreamWriter(oWriteStream, System.Text.Encoding.Default)

                Try
                    oFileWriter.Write(oStringBuilder.ToString)
                Catch err As Exception
                    Throw New Exception("Impossible d'écrire le fichier de sortie " & OutPutFile)
                End Try
                oFileWriter.Close()
                Return 0
            Else
                Throw New Exception("Impossible de lire le fichier " & FilePath)
            End If
        Else
            Throw New Exception("Impossible de trouver le fichier " & FilePath)
        End If
    End Function

    Private Sub CreateKeyArray()
        Dim KeyLen As Integer
        Dim T As Integer
        Dim i As Integer = 0
        Dim j As Integer = 0
        Dim lItem As Integer

        If Key.Trim.Length > 0 Then

            KeyLen = cls_Key.Length

            For i = 0 To 255
                S(i) = i
            Next i

            For i = 0 To 255
                j = (j + S(i) + Asc(cls_Key.Substring(i Mod KeyLen, 1)) And 255)
                T = S(i)
                S(i) = S(j)
                S(j) = T
            Next i
            i = 0
            j = 0
        Else
            Throw New System.ArgumentException("La clef est vide")
        End If

    End Sub

    Public Overloads Function GenerateKey() As String
        Dim keyBuffer As New StringBuilder
        Dim KeyLen As Short = 255
        Dim i As Integer

        Randomize(Now.Millisecond)

        Do Until i >= KeyLen
            keyBuffer.Append(Chr(CInt(255 * Rnd())))
            i += 1
        Loop

        Me.Key = keyBuffer.ToString
        Return keyBuffer.ToString

    End Function

    Public Overloads Function GenerateKey(ByVal KeyLen As Integer) As String
        Dim keyBuffer As New StringBuilder
        Dim i As Integer

        Randomize(Now.Millisecond)

        Do Until i >= KeyLen
            keyBuffer.Append(Chr(CInt(255 * Rnd())))
            i += 1
        Loop

        Me.Key = keyBuffer.ToString
        Return keyBuffer.ToString

    End Function

    Public Overloads Function GenerateKey(ByVal KeyLen As Integer, ByVal Readable As Boolean) As String
        Dim keyBuffer As New StringBuilder
        Dim AvailableChar As String = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
        Dim lenAvailableChar As Integer = AvailableChar.Length - 1
        Dim i As Integer

        Randomize(Now.Millisecond)

        If Readable = True Then
            Do Until i >= KeyLen
                keyBuffer.Append(AvailableChar.Substring(CType(lenAvailableChar * Rnd(), Integer), 1))
                i += 1
            Loop
        Else
            Do Until i >= KeyLen
                keyBuffer.Append(Chr(CInt(255 * Rnd())))
                i += 1
            Loop
        End If
        Me.Key = keyBuffer.ToString
        Return keyBuffer.ToString

    End Function

    Public Overloads Function GenerateKey(ByVal KeyLen As Integer, ByVal AvailableChar As String) As String
        Dim keyBuffer As New StringBuilder
        Dim lenAvailableChar As Integer = AvailableChar.Length - 1
        Dim i As Integer

        Randomize(Now.Millisecond)

        Do Until i >= KeyLen
            keyBuffer.Append(AvailableChar.Substring(CType(lenAvailableChar * Rnd(), Integer), 1))
            i += 1
        Loop

        Me.Key = keyBuffer.ToString
        Return keyBuffer.ToString

    End Function

End Class

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