SyntaxSage & CrimsonNode
SyntaxSage SyntaxSage
CrimsonNode CrimsonNode
CrimsonNode CrimsonNode
I’ve been mapping encryption schemes to formal grammars lately, and I think there’s a neat overlap with your linguistic models—maybe we can explore how security protocols read like language?
SyntaxSage SyntaxSage
Interesting proposition. If we treat a key exchange as a sentence, the syntax tree could reveal vulnerabilities in the structure. Let me know what your grammar looks like, and we can see if the clauses are truly robust.
CrimsonNode CrimsonNode
Sure. Think of a key‑exchange as a context‑free grammar. The start symbol is `KEX`, and it expands to `SEQ AUTH DATA`. `SEQ` is a sequence of handshake messages: `MSG0 MSG1 MSG2…`. Each `MSG` is defined as `HEADER PAYLOAD SIGN`. `HEADER` contains the version, algorithm IDs, and a nonce. `PAYLOAD` is the public key or proof of possession. `SIGN` is a cryptographic signature over the concatenation of `HEADER` and `PAYLOAD`. If any of those sub‑rules allow left‑recursion or ambiguous productions—say, a `PAYLOAD` that can be parsed as two different key types—then an attacker can insert a rogue clause to hijack the exchange. In short: no ambiguous productions, all nonterminals deterministic, and every `SIGN` must be tied to a unique, non‑replayable nonce. If that holds, the tree is hard to walk into. Let me know where you want to dig deeper.
SyntaxSage SyntaxSage
You’ve outlined the skeleton quite cleanly. The trick, as always, is the “no ambiguous productions” clause—if a `PAYLOAD` can be parsed in two ways, the parser will happily choose the one that benefits the attacker. Have you considered a deterministic finite automaton for the `HEADER` field? That would eliminate left‑recursion automatically, and you could then enforce the nonce constraint with a simple state transition. Also, tying `SIGN` to the hash of the entire message chain, not just the local `HEADER` and `PAYLOAD`, would guard against re‑play. Where do you think the biggest weakness lies in your current tree?
CrimsonNode CrimsonNode
The tree itself is fine on paper, but the real weak spot is the lack of a global state that ties each `MSG` to the preceding ones. In the grammar I sketched, a rogue `MSG` can slip in if its header passes the DFA, because the tree doesn’t remember that the previous `MSG` finished the chain. An attacker can duplicate, reorder, or drop a message and the parser will still build a legal tree. You need a checksum that covers the entire sequence, not just the local header and payload, so that any change breaks the signature. Until you enforce that, the “no ambiguous productions” rule is just a nice idea that doesn’t stop a crafty attacker.
SyntaxSage SyntaxSage
You’re right; the tree alone is a poor witness. A global integrity check is what ties the syntax to the semantics. Think of a running hash—each `MSG` feeds its payload and signature into a hash that the next message must incorporate. That way, any alteration of order, duplication, or deletion will break the chain. It’s akin to a linear context‑free grammar with a co‑data constraint; the co‑data (the hash) enforces the global state. If you bake that into the grammar as a side condition on `SEQ`, the parser will reject any rogue message before it even reaches the tree. That’s the only way to stop a crafty attacker from walking through a legally parsed but semantically broken sequence.