|
|
@@ -15,6 +15,44 @@ Overview:
|
|
|
|
|
|
This is an open proposal.
|
|
|
|
|
|
+Motivation:
|
|
|
+
|
|
|
+ Our *current* approach to versioning the Tor protocol(s) has been as
|
|
|
+ follows:
|
|
|
+ - All changes must be backward compatible.
|
|
|
+ - It's okay to add new cell types, if they would be ignored by previous
|
|
|
+ versions of Tor.
|
|
|
+ - It's okay to add new data elements to cells, if they would have been
|
|
|
+ ignored by previous versions of Tor.
|
|
|
+ - For forward compatibility, Tor must ignore cell types it doesn't
|
|
|
+ recognize, and ignore data in those cells it doesn't expect.
|
|
|
+ - Clients can inspect the version of Tor declared in the platform line
|
|
|
+ of a router's descriptor, and use that to learn whether a server
|
|
|
+ supports a given feature. Servers, however, aren't assumed to all
|
|
|
+ know about each other, and so don't know the version of who they're
|
|
|
+ talking to.
|
|
|
+
|
|
|
+ This system has these problems:
|
|
|
+ - It's very hard to change fundamental aspects of the protocol, like the
|
|
|
+ cell format, the link protocol, any of the various encryption schemes,
|
|
|
+ and so on.
|
|
|
+ - The router-to-router link protocol has remained more-or-less frozen
|
|
|
+ for a long time, since we can't easily have an OR use new features
|
|
|
+ unless it knows the other OR will understand them.
|
|
|
+
|
|
|
+ We need to resolve these problems because:
|
|
|
+ - Our cipher suite is showing its age: SHA1/AES128/RSA1024/DH1024 will
|
|
|
+ not seem like the best idea for all time.
|
|
|
+ - There are many ideas circulating for multiple cell sizes; while it's
|
|
|
+ not obvious whether these are safe, we can't do them at all without a
|
|
|
+ mechanism to permit them.
|
|
|
+ - There are many ideas circulating for alternative cell relay rules:
|
|
|
+ they don't work unless they can coexist in the current network.
|
|
|
+ - If our protocol changes a lot, it's hard to describe any coherent
|
|
|
+ version of it: we need to say "the version that Tor versions W through
|
|
|
+ X use when talking to versions Y through Z". This makes analysis
|
|
|
+ harder.
|
|
|
+
|
|
|
Proposal:
|
|
|
|
|
|
1.0. Version numbers
|
Nick Mathewson