Convert VB6 AES Rijndael Block Cipher to C # by Phil Fresle

Question

I am converting a classic asp application to C # and want to be able to decrypt strings in C # that were originally encrypted in classic asp. classic asp code is here , and C # code is here . The problem I am facing is that the signatures of the encryption and decryption methods in asp vs C # are different. here is my asp decryption code that wraps the decrypted code.

Function AESDecrypt(sCypher)
 if sCypher <> "" then

    Dim bytIn()
    Dim bytOut
    Dim bytPassword()
    Dim lCount
    Dim lLength
    Dim sTemp
    Dim sPassword 
    sPassword = "My_Password"

    lLength = Len(sCypher)
    ReDim bytIn(lLength/2-1)
    For lCount = 0 To lLength/2-1
        bytIn(lCount) = CByte("&H" & Mid(sCypher,lCount*2+1,2))
    Next
    lLength = Len(sPassword)
    ReDim bytPassword(lLength-1)
    For lCount = 1 To lLength
        bytPassword(lCount-1) = CByte(AscB(Mid(sPassword,lCount,1)))
    Next

    bytOut = DecryptData(bytIn, bytPassword)  //' this is the problem child

    lLength = UBound(bytOut) + 1
    sTemp = ""
    For lCount = 0 To lLength - 1
        sTemp = sTemp & Chr(bytOut(lCount))
    Next

    AESDecrypt = sTemp
 End if 
End Function

However, in C # I am struggling to convert this function because the C # equivalent of DecryptData has more parameters

public static byte[] DecryptData(byte[] message, byte[] password, 
            byte[] initialisationVector, BlockSize blockSize, 
            KeySize keySize, EncryptionMode cryptMode)
        {...}

what values ​​can I use to initialize Vector, blockSize, keySize, cryptMode to be able to decrypt the same as the classic asp code.

Answer 1

Phil Fresle # Rijndael, , , Phil ASP/VBScript.

: / ASP ASP.NET

    public string DecryptData(string encryptedMessage, string password)
    {
        if (encryptedMessage.Length % 2 == 1)
            throw new Exception("The binary key cannot have an odd number of digits");

        byte[] byteArr = new byte[encryptedMessage.Length / 2];
        for (int index = 0; index < byteArr.Length; index++)
        {
            string byteValue = encryptedMessage.Substring(index * 2, 2);
            byteArr[index] = byte.Parse(byteValue, NumberStyles.HexNumber, CultureInfo.InvariantCulture);
        }


        byte[] result = Rijndael.DecryptData(
            byteArr,
            Encoding.ASCII.GetBytes(password),
            new byte[] { }, // Initialization vector
            Rijndael.BlockSize.Block256, // Typically 128 in most implementations
            Rijndael.KeySize.Key256,
            Rijndael.EncryptionMode.ModeECB // Rijndael.EncryptionMode.ModeCBC
        );

        return ASCIIEncoding.ASCII.GetString(result);
    }

128, 192 256. 128 . , 128 , , , , .

UPDATE

, ; EncryptionMode EncryptionMode.ModeECB, EncryptionMode.ModeCBC. "" (https://crypto.stackexchange.com/questions/225/should-i-use-ecb-or-cbc-encryption-mode-for-my-block-cipher), , CBC, VB.

, CBC ECB ( , ), , VB , , EncryptionMode.ModeECB