move URL relevant to footnote 2

[Imported from Trac: page NewCaps/WhatCouldGoWrong, version 26]

NewCaps/WhatCouldGoWrong.md

@@ -21,7 +21,7 @@ where *k* = bitlength(*K1*), *n* = bitlength(*R*), *s* = bitlength(*S*), *t* = b
 
 1. *shape-shifter immutable file*: creator creates more than one file matching the immutable file readcap
 
-2. *roadblock*: attacker prevents uploader (including repairer) from being able to write a real share into the right storage index; *speedbump*: attacker adds his bogus share into the list of shares stored under the storage index by the same method; downloader has to download, examine, and discard the bogus (*K1enc*,*Dhash*,*V*)'s until it finds the real one
+2. *roadblock*: attacker prevents uploader (including repairer) from being able to write a real share into the right storage index; *speedbump*: attacker adds his bogus share into the list of shares stored under the storage index by the same method; downloader has to download, examine, and discard the bogus (*K1enc*,*Dhash*,*V*)'s until it finds the real one. Also see <http://allmydata.org/pipermail/tahoe-dev/2009-October/002959.html>
 
 3. *undeletion*: attacker makes a deleted file (for which it need not have had a read cap) accessible at its previous storage index, and readable by previous read caps
 
@@ -30,6 +30,3 @@ where *k* = bitlength(*K1*), *n* = bitlength(*R*), *s* = bitlength(*S*), *t* = b
 5. Brute force costs assume a single-target attack that is expected to succeed with high probability. Costs will be lower for attacking multiple targets or for a lower success probability. (Should we give explicit formulae for this?)
 
 6. *roadblock*/*speedbump* attacks could be restricted to holders of a read cap by use of an extra signature, as in the Elk Point 3 design (diagram at <http://jacaranda.org/tahoe/mutable-addonly-elkpoint-3.svg> for mutable files).
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-<http://allmydata.org/pipermail/tahoe-dev/2009-October/002959.html>