Merge pull request #31 from jyasskin/improve-def-of-threat-model

Fix #29: improve the definition of a threat model.

Author: samuelweiler

index.bs

@@ -68,8 +68,8 @@ the target threat model.
 # Introduction # {#intro}
 
 As a **threat model**, this specification describes attacker capabilities and
-attacker goals, and says which goals which capabilities should and should not
-enable.
+attacker goals, and says, for each possible set of capabilities an attacker
+might have, which goals we expect the attacker can achieve.
 
 As a **privacy** threat model, the attacker goals compromise the privacy of
 users, rather than their security.