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Diffstat (limited to 'doc/tor-spec.txt')
| -rw-r--r-- | doc/tor-spec.txt | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/doc/tor-spec.txt b/doc/tor-spec.txt index 95e724287..7efcc87a7 100644 --- a/doc/tor-spec.txt +++ b/doc/tor-spec.txt @@ -198,13 +198,19 @@ TODO: (very soon) DH data (g^y) [128 bytes] Derivative key data (KH) [20 bytes] <see 4.2 below> - The CircID for a CREATE cell is an arbitrarily chosen 2-byte - integer, selected by the node (OP or OR) that sends the CREATE - cell. To prevent CircID collisions, when one OR sends a CREATE - cell to another, it chooses from only one half of the possible - values based on the ORs' nicknames: if the sending OR has a - lexicographically earlier nickname, it chooses a CircID with a high - bit of 0; otherwise, it chooses a CircID with a high bit of 1. + The CircID for a CREATE cell is an arbitrarily chosen 2-byte integer, + selected by the node (OP or OR) that sends the CREATE cell. To prevent + CircID collisions, when one OR sends a CREATE cell to another, it chooses + from only one half of the possible values based on the ORs' public + identity keys: if the sending OR has a lower key, it chooses a CircID with + an MSB of 0; otherwise, it chooses a CircID with an MSB of 1. + + Public keys are compared numerically by modulus. + + (Older versions of Tor compared OR nicknames, and did it in a broken and + unreliable way. To support versions of Tor earlier than 0.0.9pre6, + implementations should notice when the other side of a connection is + sending CREATE cells with the "wrong" MSG, and switch accordingly.) 4.2. Setting circuit keys |