Imports System.Text
Imports System.Security.Cryptography

    Private Const CRYPT_MODE_CBC = 1
    Private Const CALC_3DES = 26115
    Private Const CALG_SHA1 = 32772

    Public Function MBI_Encrypt(ByVal key As String, ByVal nonce As String) As String
        Dim key1() As Byte, key2 As String, key3 As String, hash() As Byte, alg2 As HMACSHA1
        Dim alg3 As TripleDESCryptoServiceProvider, iv(), gg() As Byte
        Dim akm As ICryptoTransform, blob As String, kk(71) As Byte
        key1 = Convert.FromBase64String(key)
        key2 = derive_key(key1, "WS-SecureConversationSESSION KEY HASH")
        key3 = derive_key(key1, "WS-SecureConversationSESSION KEY ENCRYPTION")
        alg2 = HMACSHA1.Create
        alg2.Key = Encoding.Default.GetBytes(key2)
        hash = alg2.ComputeHash(Encoding.Default.GetBytes(nonce))
        Randomize()
        iv = Encoding.Default.GetBytes(Mid(Convert.ToBase64String(Encoding.Default.GetBytes(Rnd())), 4, 8))
        alg3 = TripleDESCryptoServiceProvider.Create
        alg3.Key = Encoding.Default.GetBytes(key3)
        alg3.Mode = CipherMode.CBC
        alg3.IV = iv
        akm = alg3.CreateEncryptor
        gg = Encoding.Default.GetBytes(nonce & Chr(8) & Chr(8) & Chr(8) & Chr(8) & Chr(8) & Chr(8) & Chr(8) & Chr(8))
        akm.TransformBlock(gg, 0, gg.Length, kk, 0)
        blob = MakeDWord(28) & MakeDWord(CRYPT_MODE_CBC) & MakeDWord(CALC_3DES) & MakeDWord(CALG_SHA1) & MakeDWord(iv.Length) & MakeDWord(hash.Length) & MakeDWord(kk.Length) & _
        Encoding.Default.GetString(iv) & Encoding.Default.GetString(hash) & Encoding.Default.GetString(kk)
        Return Convert.ToBase64String(Encoding.Default.GetBytes(blob))
    End Function
    Private Function derive_key(ByVal key() As Byte, ByVal magic As String) As String
        Dim alg1 As HMACSHA1, hash1(), hash2(), hash3(), hash4() As Byte, magicb() As Byte
        magicb = Encoding.Default.GetBytes(magic)
        alg1 = HMACSHA1.Create
        alg1.Key = key
        hash1 = alg1.ComputeHash(magicb)
        hash2 = alg1.ComputeHash(Encoding.Default.GetBytes(Encoding.Default.GetString(hash1) & magic))
        hash3 = alg1.ComputeHash(hash1)
        hash4 = alg1.ComputeHash(Encoding.Default.GetBytes(Encoding.Default.GetString(hash3) & magic))
        Return Encoding.Default.GetString(hash2) & Mid(Encoding.Default.GetString(hash4), 1, 4)
    End Function