Android Question AES Encryption Equivalent in B4A

[Jakes72]

Hi Experts / Awesome people,

If someone could please help me.
I am looking for the equivalent code in B4A for this VB.Net code:

 Public Function EncryptAES(ByVal stringToEncrypt As String, ByVal sEncryptionKey As String) As String

        Dim EncryptionKey As String = sEncryptionKey

        Dim clearBytes As Byte() = Encoding.ASCII.GetBytes(stringToEncrypt)

        Using encryptor As Aes = Aes.Create()

            Dim pdb As New Rfc2898DeriveBytes(EncryptionKey, New Byte() {211, 5, 233, 24, 55, 166, 7, 88, 2, 1, 4, 5, 6, 7, 8, 0})

            encryptor.Key = pdb.GetBytes(32)
            encryptor.IV = pdb.GetBytes(16)

            Using ms As New MemoryStream()
                Using cs As New CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write)
                    cs.Write(clearBytes, 0, clearBytes.Length)
                    cs.Close()
                End Using
                stringToEncrypt = Convert.ToBase64String(ms.ToArray())
            End Using

        End Using

        Return stringToEncrypt

End Function

Thank you in advance for your time!

Regards,
Jacques.

 

[mcqueccu]

Is this encryption method different from the numerous ones we already have?

Search Results

www.b4x.com

 

[Jakes72]

Hi Mcqueccu,

No it is not different, but I have tried this and I do not get the same result:

Sub EncryptAES(strDataToEncrypt As String, strKey As String) As String

    Dim kg As KeyGenerator
    Dim c As Cipher
    Dim B64 As Base64
    Dim bconv As ByteConverter

    Dim data(0) As Byte
    Dim iv(0) As Byte
    iv = Array As Byte(211, 5, 233, 24, 55, 166, 7, 88, 2, 1, 4, 5, 6, 7 ,8, 0) ' 16 bytes for AES
     
    c.Initialize("AES/CBC/PKCS5Padding")
    c.InitialisationVector = iv
    kg.Initialize("AES")
 
    kg.KeyFromBytes(bconv.StringToBytes(strKey,"ASCII"))
    data = bconv.StringToBytes(strDataToEncrypt, "ASCII")
    data = c.Encrypt(data, kg.Key, True)

    Return B64.EncodeBtoS(data, 0, data.Length)
 
End Sub

I have basically no knowledge of this so I am kinda 'winging' it here and just trying random stuff, can you possibly see what I am doing wrong?

 

[mcqueccu]

Try the one in this thread and possibly the solution given

[SOLVED] VB.NET and B4A AES Encryption Problem

Still having trouble with encryption. I need to be able to encrypt/decrypt the same string in both B4A and VB.NET and get the same result. I am using the same input string and key in the code below but getting two different results. I don't know enough about encryption to understand why. B4A...

www.b4x.com

 

[Jakes72]

Thanks I will have a look at that and revert back.

 

[Jakes72]

Thank you Sir for that link you are awesome!

I did not have the Decrypt methods for .NET & B4A, but I managed to figure them out with trial and error.

For anyone else battling with this and needing to pass Encrypted data between your Apps & and VB.Net program, here is the complete code:

VB.NET:

Public Function EncryptAES(ByVal stringToEncrypt As String, ByVal sEncryptionKey As String) As String

        Dim AES As New RijndaelManaged
        Dim Hash_AES As New MD5CryptoServiceProvider
        Dim encrypted As String = ""

        Try

            Dim temp As Byte() = Hash_AES.ComputeHash(ASCIIEncoding.ASCII.GetBytes(sEncryptionKey))
            AES.Key = temp
            AES.Mode = CipherMode.ECB

            Dim AESEncrypter As ICryptoTransform = AES.CreateEncryptor

            Dim Buffer As Byte() = ASCIIEncoding.ASCII.GetBytes(stringToEncrypt)
            encrypted = Convert.ToBase64String(AESEncrypter.TransformFinalBlock(Buffer, 0, Buffer.Length))
            Return encrypted

        Catch ex As Exception
        End Try

    End Function


    Public Function DecryptAES(ByVal stringToDecrypt As String, ByVal sEncryptionKey As String) As String

        Dim AES As New RijndaelManaged
        Dim Hash_AES As New MD5CryptoServiceProvider
        Dim Decrypted As String = ""

        stringToDecrypt = stringToDecrypt.Replace(" ", "+")

        Try

            Dim temp As Byte() = Hash_AES.ComputeHash(ASCIIEncoding.ASCII.GetBytes(sEncryptionKey))
            AES.Key = temp
            AES.Mode = CipherMode.ECB

            Dim AESDecrypter As ICryptoTransform = AES.CreateDecryptor

            Dim Buffer As Byte() = Convert.FromBase64String(stringToDecrypt)
            Decrypted = System.Text.Encoding.ASCII.GetString(AESDecrypter.TransformFinalBlock(Buffer, 0, Buffer.Length))
            Return Decrypted

        Catch ex As Exception
        End Try


    End Function

B4A:

Sub EncryptAES(strDataToEncrypt As String, strKey As String) As String
  
    Dim SU As StringUtils
    Dim kg As KeyGenerator
    Dim C As Cipher
    Dim md As MessageDigest
    Dim encrypted() As Byte
    kg.Initialize("AES")
    kg.KeyFromBytes(md.GetMessageDigest(strKey.GetBytes("UTF8"), "MD5"))
    
    C.Initialize("AES/ECB/PKCS5Padding")
    encrypted = C.Encrypt(strDataToEncrypt.GetBytes("UTF8"), kg.Key, False)
    Return SU.EncodeBase64(encrypted)

End Sub


Sub DecryptAES(strDataToDecrypt As String, strKey As String) As String
  
    Dim SU As StringUtils
    Dim kg As KeyGenerator
    Dim C As Cipher
    Dim md As MessageDigest
    Dim Decrypted() As Byte
    kg.Initialize("AES")
    kg.KeyFromBytes(md.GetMessageDigest(strKey.GetBytes("UTF8"), "MD5"))
    
    C.Initialize("AES/ECB/PKCS5Padding")
  
    Dim Bytes() As Byte = SU.DecodeBase64(strDataToDecrypt)
    Decrypted = C.Decrypt(Bytes, kg.Key, False)
    Return BytesToString(Decrypted, 0, Decrypted.Length, "UTF8")

End Sub