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| -rw-r--r-- | NEWS | 1 | ||||
| -rw-r--r-- | doc/methodology | 60 |
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@@ -19,6 +19,7 @@ Changes in version - 2004 * Handle situations better in which a ping receives when the last key already is expired, and the remailer no longer exists in the remailers part of the metadata (only in the addresses part). + * Add a file that describes how Echolot works. Changes in version 2.1.3 - 2004-04-20 * Improvements to pingd.conf(5) by Colin. diff --git a/doc/methodology b/doc/methodology new file mode 100644 index 0000000..e64cb1f --- /dev/null +++ b/doc/methodology @@ -0,0 +1,60 @@ + +In order to test remailer A's reliability, Echolot sends an encrypted +ping through a 1-hop chain every two hours. Pings are not sent strictly +at 02:00, 04:00 etc, but at 2h*n + f(A, date) % 2h. ( f() is a function +of the remailer name and the date of the current day (basically md5)) + +We record the timestamp each outgoing ping, and we record the time it +took to return for incoming pings. + +The reliability of a node is the result of received/sent, with the +following weighting applied: + + weight := w1 * w2; + + w1 is a function of a ping's age: + age: 1 2 3 4 5 6 7 8 9 10 11 12 [days] + weight 0.5 1.0 1.0 1.0 1.0 0.9 0.8 0.5 0.3 0.2 0.2 0.1 + + age is how long ago the ping was sent. So if a ping was sent 23 + hour ago, it weighs 0.5, if it was sent 2 days ago, its weight is 1. + Approaching 12 days, the weight approaches 0.0. + + w2 also considers this node's pings' latencies over the last 12 days: + + for pings that already returned, w2 is 1.0. + otherwise: + Let mod_age := (now - sent - 15m) * 0.8 + w2 is the fraction of pings returned within mod_age seconds. + + Example: + Assume a ping was sent 2 hours ago. mod_age is 84 minutes. If 100% + of this node's pings were faster than 84 minutes, then w2 = 1. If + only 30% were received within 84 minutes of sending out the ping, + then w2 is 0.3, If no ping was ever faster than 84 minutes, then w2 + is 0. + + +The reported latency is the median of all received pings of the last 12 +days. + + + +Chain pings are done in a similar fashion: We ping two-hop chains A, B. +Each chain is pinged once a week (with a similar offset function as +above). + +"Interesting chains" are pinged more often - daily. + +We report chains as broken if + - we sent at least 3 pings + AND + - received/sent <= rel(A) * rel(B) * 0.3. + +rel(X) is remailer X's reliability in single-hop pings. + +We define interesting chains as chains + - where we sent less than 3 pings, without getting any back. + OR + - where received/sent <= rel(A) * rel(B) * 0.3 (i.e. the chain is + reported broken) |