opc ua encrypting

[kakamo]

Hy,

I am newby in OPC UA , and i have a question about encrypting in OPC UA message. Can we decide if a paquet of OPC UA communication beetwen client and server (Message type == MSG) is encrypted just by analysing the "Encoding mask" field? if it is equale to 0x01, it mean message note encrypted, if not , the message is encrypted.

I made this conclusion from analysing wireshark capture, is it correct?

[cacamille3]

I suppose you refer "Encoding Mask" as the first byte of the Message - TypeId, which is an ExpandedNodeId,
The first Byte actually stands for the encoding DataEncoding of the NodeId of the ExpandedNodeId.

According to the OPC UA Specification the possible values are:

Two Byte: 0x00 - A numeric value that fits into the two byte representation.
Four Byte: 0x01 - A numeric value that fits into the four byte representation.
Numeric: 0x02 - A numeric value that does not fit into the two or four byte representations.
String: 0x03 - A String value.
Guid: 0x04 - A Guid value.
ByteString: 0x05 - An opaque (ByteString) value.
NamespaceUri Flag: 0x80 - See discussion of ExpandedNodeId in 5.2.2.10.
ServerIndex Flag: 0x40 - See discussion of ExpandedNodeId in 5.2.2.10.

It is well described in the OPC UA Specification Part 6 - 5.2.2.9.

[kakamo]

thanks for your reponse.
I did noticed that all encrypted message dont have any of the possible values you mentioned (for exemple, 0xed), so i suposed that by just using this filed, we can decide if a message is encrypted or not