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Subject: [no subject]
-----Original Message-----
From: Conor P. Cahill [mailto:concahill@aol.com]
Sent: Tuesday, August 31, 2004 8:44 AM
To: Mishra, Prateek
Cc: Paul Madsen; 'security-services@lists.oasis-open.org'
Subject: RE: [security-services] SessionIndex and Privacy Text
I think it would be useful to document the two common mechanisms used in
liberty solutions for this index:
a) small integer (which we have in paul's suggested text)
and b) the assertion ID itself is stored in the session index.
The second seems to have issues with the "MUST NOT be a unique..."
requirement although it doesn not violate privacy.
So, my recommended verbage:
When privacy is a concen, care must be taken to ensure that the SessionIndex
element does not invalidate other privacy mechanisms - the value MUST NOT be
usable to correlate sessions across different SPs Two recommended solutions
are provided below:
* The authority uses small positive integers (or reoccurring constants
in a list) for the SessionIndex, then it SHOULD choose the range of values
such that the cardinality of any one integer will be sufficiently high to
prevent a particular user's actions from being correlated across multiple
service providers. The authority SHOULD choose values for SessionIndex
randomly from within this range (except when required to ensure unique
values for subsequent AuthnStatements to the same service provider).
* The authority uses the Assertion ID value in the Session Index
element.
*
Hmm... Thinking about this, we could just move to using the assertion ID
since storing that value at the SP is little different than storing the
session index and for the IDP, they probably keep track of the assertion IDs
that they have issued at least for the lifetime of the assertion.
If we did use the Assertion ID, we could simply get rid of the session
index.
Thoughts?
Conor
Mishra, Prateek wrote on 8/30/2004, 4:32 PM:
+1. We just finished puzzling over the “small integer” suggestion. In any
case, as the proposed text suggests, this issue is relevant only when
privacy is a concern (admittedly often).
- prateek
_____
From: Paul Madsen [ mailto:p.madsen@entrust.com
<mailto:p.madsen@entrust.com> ]
Sent: Wednesday, August 25, 2004 3:26 PM
To: ' security-services@lists.oasis-open.org
<mailto:security-services@lists.oasis-open.org> '
Subject: [security-services] SessionIndex and Privacy Text
Hi, some comments on Lines 977-981 in Core
1) its not clear to me whether this requirement is normative on all
deployments or only on those for which privacy is a issue. The preface 'For
privacy reasons' somewhat gives the impression that this is a general
requirement. This contrasted to potential alternative text e.g. '*When*
privacy is a concern ...'
2) when combined with the previous 'SHOULD be a small, positive integer',
the 'MUST NOT be reused in subsequent assertions
given to different relying parties about the same principal' seems
contradictory
a) if small integers are used for SessionIndex, then for any reasonable
number of simultaneously logged in users, the high cardinality of the
individual SessionIndex values will prevent their use by rogue SPs for
collusion, i.e. there will so be many users all with SessionIndex of '3'
that no two SPs will be able to use this value to pinpoint a particular
user. This is acknowledged by the last sentence of the para, 'MAY be a small
integer value that is used in assertions issued on behalf of many different
subjects at the same time'. Consequently, the restriction against reuse
seems overconstraining.
I imagine that the MUST NOT reuse rule is motivated by the potential for the
SessionIndex value to be something other than a small integer. We could
differentiate these cases given their different aspects.
b) if rogue SPs know that the IDP MUST NOT reuse SessionIndex values,
this actually gives them more information than if the IDP were to simply
insert random values (possibly within some defined range) for the
SessionIndex. For instance, if two SPs are comparing logs for a bunch of
users they know were simultaneously logged in at IDP, <AuthnStatement>s with
the same SessionIndex can only be for different users and so can be
discarded. A bonus would be that the IDP would no longer need to keep
track of which SessionIndex's were used inter-SP (it would still need to
intra-SP)
My proposed replacement text
When privacy is a concen, care must be taken to ensure that the SessionIndex
element does not invalidate other privacy mechanisms - the value MUST NOT be
a unique value identifying a principal's session at the authority.
If the authority uses small positive integers (or reoccurring constants in a
list) for the SessionIndex, then it SHOULD choose the range of values such
that the cardinality of any one integer will be sufficiently high to prevent
a particular user's actions from being correlated across multiple service
providers. The authority SHOULD choose values for SessionIndex randomly from
within this range (except when required to ensure unique values for
subsequent AuthnStatements to the same service provider).
if the authority uses some other scheme for the SessionIndex attribute, it
SHOULD choose values for SessionIndex randomly.
Paul
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<DIV><SPAN class=593583912-31082004><FONT face=Arial color=#0000ff size=2>When I
read thru the Liberty specs, it seem to imply that the session index was a way
to represent different sessions for a single user. For example, a user using 2
machines/browsers to log in. Consider the case where a user only logs in
once at an IDP (assume it gets assigned session index value of 1), and then uses
that authentication/session at the IDP to authenticate to various other SPs. My
take from the Liberty specs was that the session index for all the SPs could be
set to 1. In general if thousands of users log in from a single machine/browser
only, their session index would have a value 1.</FONT></SPAN></DIV>
<DIV><SPAN class=593583912-31082004><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=593583912-31082004><FONT face=Arial color=#0000ff
size=2>Eventually, there might be some users that log in from a second machine
to an IDP (that session index gets the value of 2). From there, they use
that authentication to get into other SPs (perhaps the same ones as the other
session or perhaps new SPs -- that is irrelevant). The session index value of 2
would be used during an authentication response by the IDP for this case. In
general you might have hundreds of users logged in twice.</FONT></SPAN></DIV>
<DIV><SPAN class=593583912-31082004><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=593583912-31082004><FONT face=Arial color=#0000ff size=2>Taking
this further some users might log in from a third machine/browser, and so
on.</FONT></SPAN></DIV>
<DIV><SPAN class=593583912-31082004><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=593583912-31082004><FONT face=Arial color=#0000ff size=2>So my
question is, if we use the same session index value for all SPs
(if the authentication is based on the same IDP session) why is
privacy an issue. In general, an SP site would see thousands of 1's, hundreds of
2's, tens of 3's, etc... And because users can go to arbitrary SPs, it is
extremely unlikely that you can match up these session
indexes.</FONT></SPAN></DIV>
<DIV><SPAN class=593583912-31082004><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=593583912-31082004><FONT face=Arial color=#0000ff size=2>From
the Liberty specs and from a technical perspective, I took the need for a
session index as a requirement to be able to logout users on a per
machine/browser basis. So if the original user browser session above is being
logged out (session index value of 1), the other session (value of 2), should
not be affected.</FONT></SPAN></DIV>
<DIV><SPAN class=593583912-31082004><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=593583912-31082004><FONT face=Arial color=#0000ff
size=2>Thanks, Tom.</FONT></SPAN></DIV>
<BLOCKQUOTE>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B> Conor P. Cahill
[mailto:concahill@aol.com]<BR><B>Sent:</B> Tuesday, August 31, 2004 8:44
AM<BR><B>To:</B> Mishra, Prateek<BR><B>Cc:</B> Paul Madsen;
'security-services@lists.oasis-open.org'<BR><B>Subject:</B> RE:
[security-services] SessionIndex and Privacy Text<BR><BR></FONT></DIV><FONT
face="Comic Sans MS,sans-serif"><FONT size=2><BR>I think it would be useful to
document the two common mechanisms used in liberty solutions for this
index:<BR><BR> a) small integer (which we
have in paul's suggested text)<BR>and b) the assertion ID
itself is stored in the session index.<BR><BR>The second seems to have issues
with the "MUST NOT be a unique..." requirement although it doesn not violate
privacy.<BR><BR>So, my recommended verbage:<BR></FONT></FONT>
<P class=MsoNormal><FONT face="Comic Sans MS,sans-serif" size=2><EM><I><FONT
face="Century Gothic" size=2><FONT face="Century Gothic"><FONT size=2>When
privacy is a concen, care must be taken to ensure that the
SessionIndex element does not invalidate other privacy mechanisms - the value
MUST NOT be usable to correlate sessions across different SPs Two
recommended solutions are provided
below: </FONT></FONT></FONT></I></EM><O:P></O:P></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Times New Roman" size=3><FONT
size=3><O:P></O:P></FONT></FONT></P><FONT face="Comic Sans MS,sans-serif"
size=2></FONT></DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV>
<UL>
<LI><FONT face="Comic Sans MS,sans-serif" size=2><EM><I><FONT
face="Century Gothic" size=2><FONT face="Century Gothic"><FONT size=2>The
authority uses small positive integers (or reoccurring constants in a list)
for the SessionIndex, then it SHOULD choose the range of values such
that the cardinality of any one integer will be sufficiently high to prevent
a particular user's actions from being correlated across multiple service
providers. The authority SHOULD choose values for SessionIndex
randomly from within this range (except when required to ensure unique
values for subsequent AuthnStatements to the same service
provider).</FONT></FONT></FONT></I></EM></FONT>
<LI><FONT face="Comic Sans MS,sans-serif" size=2><I><FONT
face="Century Gothic" size=2><FONT face="Century Gothic"><FONT size=2>The
authority uses the Assertion ID value in the Session Index element.
<BR><EM></EM></FONT></FONT></FONT></I></FONT></LI></UL><EM></EM><O:P></O:P>
<UL>
<LI><FONT face="Comic Sans MS,sans-serif" size=2></FONT><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Comic Sans MS,sans-serif"
size=2><EM></EM><O:P></O:P></FONT></P><FONT face="Comic Sans MS,sans-serif"
size=2></FONT></LI></UL></DIV><FONT face="Comic Sans MS,sans-serif"
size=2></FONT><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT><FONT
face="Comic Sans MS,sans-serif" size=2></FONT><FONT face="Century Gothic"
size=2><FONT face="Century Gothic"><FONT size=2></FONT></FONT></FONT><FONT
face="Comic Sans MS,sans-serif"><FONT size=2><BR>Hmm... Thinking about this,
we could just move to using the assertion ID since storing that value at the
SP is little different than storing the session index and for the IDP, they
probably keep track of the assertion IDs that they have issued at least for
the lifetime of the assertion.<BR><BR>If we did use the Assertion ID, we could
simply get rid of the session index.<BR><BR>Thoughts?<BR><BR>Conor<BR><SPAN
type="cite">Mishra, Prateek wrote on 8/30/2004, 4:32 PM:</SPAN> </FONT></FONT>
<P><FONT face="Comic Sans MS,sans-serif" size=2></FONT></P>
<BLOCKQUOTE
style="PADDING-LEFT: 10px; MARGIN-LEFT: 0pt; BORDER-LEFT: blue thin solid"
type="cite"><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV class=Section1><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face=Arial color=blue size=3><FONT face=Arial><FONT
size=3><FONT color=blue><FONT color=blue>+1. We just finished puzzling over
the “small integer” suggestion. In any case, as the proposed text suggests,
this issue is relevant only when privacy is a concern (admittedly
often).<O:P></O:P></FONT></FONT></FONT></FONT></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face=Arial color=blue size=3><FONT face=Arial><FONT
size=3><FONT color=blue><FONT
color=blue><O:P></O:P></FONT></FONT></FONT></FONT></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face=Arial color=blue size=3><FONT face=Arial><FONT
size=3><FONT color=blue><FONT color=blue>-
prateek<O:P></O:P></FONT></FONT></FONT></FONT></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face=Arial color=blue size=3><FONT face=Arial><FONT
size=3><FONT color=blue><FONT
color=blue><O:P></O:P></FONT></FONT></FONT></FONT></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV class=MsoNormal style="TEXT-ALIGN: center" align=center><FONT
face="Times New Roman" size=3><SPAN style="FONT-SIZE: 12pt">
<HR tabIndex=-1 align=center width="100%" SIZE=2>
</SPAN></FONT></DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Comic Sans MS,sans-serif" size=2><B><FONT
face=Tahoma size=2><FONT face=Tahoma><FONT
size=2>From:</FONT></FONT></FONT></B></FONT><FONT face=Tahoma size=2><FONT
face=Tahoma><FONT size=2> Paul Madsen [<A class=moz-txt-link-freetext
href="mailto:p.madsen@entrust.com";>mailto:p.madsen@entrust.com</A>]
<BR><B><SPAN style="FONT-WEIGHT: bold">Sent:</SPAN></B> Wednesday, August
25, 2004 3:26 PM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B>
<ST1:PERSONNAME w:st="on">'<A class=moz-txt-link-abbreviated
href="mailto:security-services@lists.oasis-open.org";>security-services@lists.oasis-open.org</A>'</ST1:PERSONNAME><BR><B><SPAN
style="FONT-WEIGHT: bold">Subject:</SPAN></B> [security-services]
SessionIndex and Privacy Text</FONT></FONT></FONT><FONT
face="Comic Sans MS,sans-serif" size=2><O:P></O:P></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Century Gothic" size=2><FONT
face="Century Gothic"><FONT size=2>Hi, some comments on Lines 977-981
in Core</FONT></FONT></FONT><FONT face="Comic Sans MS,sans-serif"
size=2><O:P></O:P></FONT></P><FONT face="Comic Sans MS,sans-serif"
size=2></FONT></DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Century Gothic" size=2><FONT
face="Century Gothic"><FONT size=2>1) its not clear to me whether this
requirement is normative on all deployments or only on those for which
privacy is a issue. The preface 'For privacy reasons' somewhat gives the
impression that this is a general requirement. This contrasted to potential
alternative text e.g. '*When* privacy is a concern
...'</FONT></FONT></FONT><FONT face="Comic Sans MS,sans-serif"
size=2><O:P></O:P></FONT></P><FONT face="Comic Sans MS,sans-serif"
size=2></FONT></DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Century Gothic" size=2><FONT
face="Century Gothic"><FONT size=2>2) when combined with the previous
'</FONT></FONT></FONT><FONT face=ArialMT size=2><FONT face=ArialMT><FONT
size=2>SHOULD be a small, positive integer', </FONT></FONT></FONT><FONT
face="Century Gothic" size=2><FONT face="Century Gothic"><FONT size=2>the
'MUST NOT be reused in subsequent assertions<BR>given to different relying
parties about the same principal' seems
contradictory</FONT></FONT></FONT><FONT face="Comic Sans MS,sans-serif"
size=2><O:P></O:P></FONT></P><FONT face="Comic Sans MS,sans-serif"
size=2></FONT></DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Century Gothic" size=2><FONT
face="Century Gothic"><FONT size=2> a) if small integers
are used for SessionIndex, then for any reasonable number of simultaneously
logged in users, the high cardinality of the individual SessionIndex values
will prevent their use by rogue SPs for collusion, i.e. there will so be
many users all with SessionIndex of '3' that no two SPs will be able to
use this value to pinpoint a particular user. This is acknowledged
by the last sentence of the para, 'MAY be a small integer value that is used
in assertions issued on behalf of many different subjects at the same time'.
Consequently, the restriction against reuse seems
overconstraining.</FONT></FONT></FONT><FONT face="Comic Sans MS,sans-serif"
size=2><O:P></O:P></FONT></P><FONT face="Comic Sans MS,sans-serif"
size=2></FONT></DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Century Gothic" size=2><FONT
face="Century Gothic"><FONT size=2>I imagine that the MUST NOT reuse rule is
motivated by the potential for the SessionIndex value to be something other
than a small integer. We could differentiate these cases given their
different aspects.</FONT></FONT></FONT><FONT face="Comic Sans MS,sans-serif"
size=2><O:P></O:P></FONT></P><FONT face="Comic Sans MS,sans-serif"
size=2></FONT></DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Century Gothic" size=2><FONT
face="Century Gothic"><FONT size=2> b) if rogue SPs know
that the IDP MUST NOT reuse SessionIndex values, this actually gives them
more information than if the IDP were to simply insert random values
(possibly within some defined range) for the SessionIndex. For
instance, if two SPs are comparing logs for a bunch of users they know were
simultaneously logged in at IDP, <AuthnStatement>s with the same
SessionIndex can only be for different users and so can be discarded.
A bonus would be that the IDP would no longer need to keep track
of which SessionIndex's were used inter-SP (it would still need to
intra-SP)</FONT></FONT></FONT><FONT face="Comic Sans MS,sans-serif"
size=2><O:P></O:P></FONT></P><FONT face="Comic Sans MS,sans-serif"
size=2></FONT></DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Century Gothic" size=2><FONT
face="Century Gothic"><FONT size=2>My proposed replacement
text</FONT></FONT></FONT><FONT face="Comic Sans MS,sans-serif"
size=2><O:P></O:P></FONT></P><FONT face="Comic Sans MS,sans-serif"
size=2></FONT></DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Comic Sans MS,sans-serif" size=2><EM><I><FONT
face="Century Gothic" size=2><FONT face="Century Gothic"><FONT size=2>When
privacy is a concen, care must be taken to ensure that the
SessionIndex element does not invalidate other privacy mechanisms - the
value MUST NOT be a unique value identifying a principal's session at the
authority. </FONT></FONT></FONT></I></EM><O:P></O:P></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Comic Sans MS,sans-serif" size=2><EM><I><FONT
face="Century Gothic" size=2><FONT face="Century Gothic"><FONT size=2>If the
authority uses small positive integers (or reoccurring constants in a list)
for the SessionIndex, then it SHOULD choose the range of values such
that the cardinality of any one integer will be sufficiently high to prevent
a particular user's actions from being correlated across multiple service
providers. The authority SHOULD choose values for SessionIndex
randomly from within this range (except when required to ensure unique
values for subsequent AuthnStatements to the same service
provider).</FONT></FONT></FONT></I></EM><O:P></O:P></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Comic Sans MS,sans-serif" size=2><EM><I><FONT
face="Century Gothic" size=2><FONT face="Century Gothic"><FONT size=2>if
the authority uses some other scheme for the SessionIndex
attribute, it SHOULD choose values for SessionIndex
randomly.</FONT></FONT></FONT></I></EM><O:P></O:P></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Century Gothic" size=2><FONT
face="Century Gothic"><FONT size=2><BR></FONT></FONT></FONT><FONT
face="Comic Sans MS,sans-serif" size=2> <O:P></O:P></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Century Gothic" size=2><FONT
face="Century Gothic"><FONT size=2>Paul </FONT></FONT></FONT><FONT
face="Comic Sans MS,sans-serif" size=2><O:P></O:P></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Comic Sans MS,sans-serif"
size=2><STRONG><B><FONT face=Arial size=2><FONT face=Arial><FONT
size=2>-----------------------------------------------------------------</FONT></FONT></FONT></B></STRONG><O:P></O:P></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Comic Sans MS,sans-serif"
size=2><STRONG><B><FONT face="Bookman Old Style" size=2><FONT
face="Bookman Old Style"><FONT size=2>Paul
Madsen</FONT></FONT></FONT></B></STRONG><O:P></O:P></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Bookman Old Style" size=2><FONT
face="Bookman Old Style"><FONT size=2>e: </FONT></FONT></FONT><FONT
face="Comic Sans MS,sans-serif" size=2><A
href="mailto:p.madsen@entrust.com";><FONT face="Bookman Old Style"
size=2><FONT face="Bookman Old Style"><FONT
size=2>p.madsen@entrust.com</FONT></FONT></FONT></A><O:P></O:P></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Bookman Old Style" size=2><FONT
face="Bookman Old Style"><FONT size=2>p:
613-270-2632</FONT></FONT></FONT><FONT face="Comic Sans MS,sans-serif"
size=2><O:P></O:P></FONT></P><FONT face="Comic Sans MS,sans-serif"
size=2></FONT></DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Bookman Old Style" size=2><FONT
face="Bookman Old Style"><FONT size=2>c:
613-799-2632</FONT></FONT></FONT><FONT face="Comic Sans MS,sans-serif"
size=2><O:P></O:P></FONT></P><FONT face="Comic Sans MS,sans-serif"
size=2></FONT></DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Bookman Old Style" size=2><FONT
face="Bookman Old Style"><FONT size=2>Entrust</FONT></FONT></FONT><FONT
face="Comic Sans MS,sans-serif" size=2><O:P></O:P></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT>
<DIV><FONT face="Comic Sans MS,sans-serif" size=2></FONT>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></FONT></P><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></DIV><FONT
face="Comic Sans MS,sans-serif" size=2></FONT></BLOCKQUOTE>To unsubscribe from
this mailing list (and be removed from the roster of the OASIS TC), go to
http://www.oasis-open.org/apps/org/workgroup/security-services/members/leave_workgroup.php.
</BLOCKQUOTE></BODY></HTML>
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