Java到VB.NET AES加密

Question

I have this code here which I'm having difficulty converting to VB.NET and hoping someone who give me a hand with it.

I'm having difficulty with the part on the cipher - I have tried Googling but was unable to find a clear resource explaining it in simple terms. (I don't know how to proceed with it as it seems there's no equivalent for it??)

I have almost no knowledge of java hence am trying to google and find out what each part means and convert it after. Hope someone would be able to point me in the right direction!

 public static byte[] decryptPDF(String password, String filePath) {
    try {
        byte[] headerSaltAndCipherText = Base64.decode(IOUtils.toString(new FileInputStream(new File(filePath)), "UTF-8").toString().getBytes("UTF-8"), 0);
        byte[] salt = Arrays.copyOfRange(headerSaltAndCipherText, 8, 16);
        byte[] encrypted = Arrays.copyOfRange(headerSaltAndCipherText, 16, headerSaltAndCipherText.length);
        Cipher aesCBC = Cipher.getInstance("AES/CBC/PKCS5Padding");
        byte[][] keyAndIV = EVP_BytesToKey(32, aesCBC.getBlockSize(), MessageDigest.getInstance(CommonUtils.MD5_INSTANCE), salt, password.getBytes("UTF-8"), 1);
        aesCBC.init(2, new SecretKeySpec(keyAndIV[0], "AES"), new IvParameterSpec(keyAndIV[1]));
        return aesCBC.doFinal(encrypted);
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    } catch (NoSuchPaddingException e2) {
        e2.printStackTrace();
        return null;
    } catch (InvalidAlgorithmParameterException e3) {
        e3.printStackTrace();
        return null;
    } catch (NoSuchAlgorithmException e4) {
        e4.printStackTrace();
        return null;
    } catch (IllegalBlockSizeException e5) {
        e5.printStackTrace();
        return null;
    } catch (BadPaddingException e6) {
        e6.printStackTrace();
        return null;
    } catch (InvalidKeyException e7) {
        e7.printStackTrace();
        return null;
    }
}

What I've tried so far is...

Public Shared Function decryptPDF(ByVal password As String, ByVal fileAsString As String) As Byte()
    Try
        Dim headerSaltAndCipherText() As Byte = System.Convert.FromBase64String(fileAsString)
        Dim salt() As Byte = headerSaltAndCipherText.Skip(7).Take(8)
        Dim encrypted() As Byte = headerSaltAndCipherText.Skip(15).Take(headerSaltAndCipherText.Length)
        Dim aesCBC As Cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
        Dim keyAndIV() As Byte = EVP_BytesToKey(32, aesCBC.getBlockSize, MessageDigest.getInstance(CommonUtils.MD5_INSTANCE), salt, password.getBytes("UTF-8"), 1)
        aesCBC.init(2, New SecretKeySpec(keyAndIV(0), "AES"), New IvParameterSpec(keyAndIV(1)))
        Return aesCBC.doFinal(encrypted)

    End Try
End Function

Answer 1

Try that

Public Shared Function decryptPDF(ByVal password As String, ByVal filePath As String) As Byte()
        Try 
            Dim headerSaltAndCipherText() As Byte = Base64.decode(IOUtils.toString(New FileInputStream(New File(filePath)), "UTF-8").toString.getBytes("UTF-8"), 0)
            Dim salt() As Byte = Arrays.copyOfRange(headerSaltAndCipherText, 8, 16)
            Dim encrypted() As Byte = Arrays.copyOfRange(headerSaltAndCipherText, 16, headerSaltAndCipherText.length)
            Dim aesCBC As Cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
            Dim keyAndIV(,) As Byte = EVP_BytesToKey(32, aesCBC.getBlockSize, MessageDigest.getInstance(CommonUtils.MD5_INSTANCE), salt, password.getBytes("UTF-8"), 1)
            aesCBC.init(2, New SecretKeySpec(keyAndIV(0), "AES"), New IvParameterSpec(keyAndIV(1)))
            Return aesCBC.doFinal(encrypted)
        Catch e As IOException
            e.printStackTrace
            Return Nothing
        Catch e2 As NoSuchPaddingException
            e2.printStackTrace
            Return Nothing
        Catch e3 As InvalidAlgorithmParameterException
            e3.printStackTrace
            Return Nothing
        Catch e4 As NoSuchAlgorithmException
            e4.printStackTrace
            Return Nothing
        Catch e5 As IllegalBlockSizeException
            e5.printStackTrace
            Return Nothing
        Catch e6 As BadPaddingException
            e6.printStackTrace
            Return Nothing
        Catch e7 As InvalidKeyException
            e7.printStackTrace
            Return Nothing
        End Try

    End Function