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Information Security
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re: Clarification on Data Integrity
Ryan Pierce / Townsend Analytics Ltd. / Archipelago LLC
24 Sep 2002 2:01PM ETSorry, two things that I should have clarified:
> Thus, FIX "signature" only protect against modification of the message over the wire. They do NOTHING to protect against fraudulent repudiation.
I overstated things here. Using a MAC makes it harder for either party to claim that some malicious third party originated the order. Someone would need to know the shared secret to generate the correct MAC, which (hopefully) limits it two the two parties. But a MAC alone cannot show which of the two parties originated the message.
Now an actual PKI signature would indicate which of the two parties signed the message. (Or, more accurately, would indicate that someone with knowledge of the private key of a specific party signed that message.)
So a FIX "signature" does make fraudulent repudiation slightly more difficult, but it doesn't have the same strength as an actual digital signature.
> We've rolled our own code for this, but it is interoperable with clients who use the FIX web site implementation. What I believe happens is that, after initializing a clean MD5 hash and hashing the session key, the entire FIX message buffer created so far gets hashed. This likely consists of the BeginString, BodyLength, and MsgType, followed by SecureDataLength and SecureData (including the [SOH] at the end.
I forgot to mention that one follows this by hashing the session key again.
re: Clarification on Data Integrity
Ryan Pierce / Townsend Analytics Ltd. / Archipelago LLC 24 Sep 2002 2:01PM ET
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