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Securing ADO.NET Connection Strings

, 25 Aug 2006
Some possible ways to encrypt and store connection strings in an ADO.NET application.
secureconnectionstring_demo.zip
Secure ADO.NET Connection String_demo
Secure ADO.NET Connection String.exe
secureconnectionstring_src.zip
Secure ADO.NET Connection String_src
My Project
Application.myapp
Settings.settings
Imports System
Imports System.Xml
Imports System.Security.Cryptography
Imports System.Security.Cryptography.Xml



Public Class Encrypt_Decrypt

    Public Shared Sub Encrypt(ByVal Doc As XmlDocument, ByVal ElementToEncryptParam As String, ByVal Alg As RSA, ByVal KeyName As String)
        ' Check the arguments.  
        If Doc Is Nothing Then
            Throw New ArgumentNullException("Doc")
        End If
        If ElementToEncryptParam Is Nothing Then
            Throw New ArgumentNullException("ElementToEncrypt")
        End If
        If Alg Is Nothing Then
            Throw New ArgumentNullException("Alg")
        End If

        ' Find the specified element in the XmlDocument
        ' object and create a new XmlElemnt object.

        Dim elementToEncrypt As XmlElement = Doc.GetElementsByTagName(ElementToEncryptParam)(0)

        ' Throw an XmlException if the element was not found.
        If elementToEncrypt Is Nothing Then
            Throw New XmlException("The specified element was not found")
        End If

        ' Create a new instance of the EncryptedXml class 
        ' and use it to encrypt the XmlElement with the 
        ' a new random symmetric key.

        ' Create a 256 bit Rijndael key, which will encrypt 
        'the XML element, and then be encrypted itself and 
        'placed in the XML document.

        Dim sessionKey As New RijndaelManaged()
        sessionKey.KeySize = 256

        Dim eXml As New EncryptedXml()

        Dim encryptedElement As Byte() = eXml.EncryptData(elementToEncrypt, sessionKey, False)

        ' Construct an EncryptedData object and populate
        ' it with the desired encryption information.
        Dim edElement As New EncryptedData()
        edElement.Type = EncryptedXml.XmlEncElementUrl

        ' Create an EncryptionMethod element so that the 
        ' receiver knows which algorithm to use for decryption.
        edElement.EncryptionMethod = New EncryptionMethod(EncryptedXml.XmlEncAES256Url)

        ' Encrypt the session key and add it to an EncryptedKey element.
        Dim ek As New EncryptedKey()

        Dim encryptedKey As Byte() = EncryptedXml.EncryptKey(sessionKey.Key, Alg, False)
        ek.CipherData = New CipherData(encryptedKey)
        ek.EncryptionMethod = New EncryptionMethod(EncryptedXml.XmlEncRSA15Url)

        ' Set the KeyInfo element to specify the
        ' name of the RSA key.
        ' Create a new KeyInfo element.
        edElement.KeyInfo = New KeyInfo()

        ' Create a new KeyInfoName element.
        Dim kin As New KeyInfoName()

        ' Specify a name for the key.
        kin.Value = KeyName

        ' Add the KeyInfoName element to the 
        ' EncryptedKey object.
        ek.KeyInfo.AddClause(kin)

        ' Add the encrypted key to the 
        ' EncryptedData object.
        edElement.KeyInfo.AddClause(New KeyInfoEncryptedKey(ek))

        ' Add the encrypted element data to the 
        ' EncryptedData object.
        edElement.CipherData.CipherValue = encryptedElement

        ' Replace the element from the original XmlDocument
        ' object with the EncryptedData element.
        EncryptedXml.ReplaceElement(elementToEncrypt, edElement, False)
    End Sub
    Public Shared Sub Decrypt(ByVal Doc As XmlDocument, ByVal Alg As RSA, ByVal KeyName As String)
        ' Check the arguments.  
        If Doc Is Nothing Then
            Throw New ArgumentNullException("Doc")
        End If
        If Alg Is Nothing Then
            Throw New ArgumentNullException("Alg")
        End If
        If KeyName Is Nothing Then
            Throw New ArgumentNullException("KeyName")
        End If
        ' Create a new EncryptedXml object.
        Dim exml As New EncryptedXml(Doc)

        ' Add a key-name mapping.
        ' This method can only decrypt documents
        ' that present the specified key name.
        exml.AddKeyNameMapping(KeyName, Alg)

        ' Decrypt the element.
        exml.DecryptDocument()
    End Sub
    Public Shared Function GenKey_SaveInContainer(ByVal ContainerName As String) As RSACryptoServiceProvider
        ' Create the CspParameters object and set the key container 
        ' name used to store the RSA key pair.
        Dim cp As New CspParameters()
        cp.KeyContainerName = ContainerName

        ' Create a new instance of RSACryptoServiceProvider that accesses
        ' the key container MyKeyContainerName.
        GenKey_SaveInContainer = New RSACryptoServiceProvider(cp)
    End Function
    Public Shared Function GetKeyFromContainer(ByVal ContainerName As String) As RSACryptoServiceProvider
        ' Create the CspParameters object and set the key container 
        '  name used to store the RSA key pair.
        Dim cp As New CspParameters()
        cp.KeyContainerName = ContainerName

        ' Create a new instance of RSACryptoServiceProvider that accesses
        ' the key container MyKeyContainerName.
        GetKeyFromContainer = New RSACryptoServiceProvider(cp)
    End Function
    Public Shared Sub DeleteKeyFromContainer(ByVal ContainerName As String)
        ' Create the CspParameters object and set the key container 
        '  name used to store the RSA key pair.
        Dim cp As New CspParameters()
        cp.KeyContainerName = ContainerName

        ' Create a new instance of RSACryptoServiceProvider that accesses
        ' the key container.
        Dim rsa As New RSACryptoServiceProvider(cp)

        ' Delete the key entry in the container.
        rsa.PersistKeyInCsp = False

        ' Call Clear to release resources and delete the key from the container.
        rsa.Clear()
    End Sub
End Class

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About the Author

Levan Midodashvili
Web Developer
Georgia Georgia
Lecturer in Gori University (Georgia)

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