Encriptación SHA1 en .NET
  

Public Shared Function GetSHA1(string str) As String 
    Dim sha1 As SHA1 = SHA1Managed.Create();
    Dim encoding As New ASCIIEncoding();
    Dim stream() As Byte() = null;

    Dim sb As new StringBuilder();
    stream = sha1.ComputeHash(encoding.GetBytes(str));

    For i = 0 To stream.Length
        sb.AppendFormat("{0:x2}", stream[i])
    Next i

    Return sb.ToString()
End Function
  

Imports System
Imports System.Security.Cryptography
Imports System.Text
Public Class GetSHA1

    Public Shared Function SHA1(text As [String]) As [String]
        Dim myString As String = text
        Dim Data As Byte()

        Data = Encoding.ASCII.GetBytes(myString)

        Dim shaM As New SHA1Managed()
        Dim resultHash As Byte() = shaM.ComputeHash(Data)

        Dim resultHexString = text
        Dim b As Byte

        For Each b In resultHash
            resultHexString += Hex(b)
        Next
        Dim b64 As String = Convert.ToBase64String(resultHash)
        Return b64
    End Function

End Class
  

Dim strEncryptedText As String = GetSHA1.SHA1("Contraseña")
        MsgBox(strEncryptedText)