Draft: draft-arkko-eap-aka-pfs

Commentary: Not sure the attacks actually attacked the smart cards . Changed to " smart card supply chain " in the abstract and intro . This is very much related to zero trust principles . a sentence about this . Any modern standard track EAP method should provide mandatory client identity protection . Copied the text from EAP - TLS 1.3 Motivation for the chosen curves is missing . Added link to the definition of SUCI encryption in appendix C.3.4 . of TS 33.501 Added more text in security consideration on the attacks an attacker can do . Added more text in security consideration on frequent use of ECDHE . 
 Great ! There 's one typo but I 'll fix it .
Many different attacks have been reported as part of revelations
associated with pervasive surveillance.  Some of the reported attacks
involved compromising smart cards, such as attacking SIM card
manufacturers and operators in an effort to compromise shared secrets
stored on these cards.  Since the publication of those reports,
manufacturing and provisioning processes have gained much scrutiny
and have improved.  However, the danger of resourceful attackers for
these systems is still a concern.
Many different attacks have been reported as part of revelations
associated with pervasive surveillance.  Some of the reported attacks
involved compromising the smart card supply chain, such as attacking
SIM card manufacturers and operators in an effort to compromise
shared secrets stored on these cards.  Since the publication of those
reports, manufacturing and provisioning processes have gained much
scrutiny and have improved.  However, the danger of resourceful
attackers for these systems is still a concern.  Always assuming
breach such as key compromise and minimizing the impact of breach are
essential zero-trust principles.
Many different attacks have been reported as part of revelations
associated with pervasive surveillance.  Some of the reported attacks
involved compromising smart cards, such as attacking SIM card
manufacturers and operators in an effort to compromise shared secrets
stored on these cards.  Such attacks are conceivable, for instance,
during the manufacturing process of cards, or during the transfer of
cards and associated information to the operator.  Since the
publication of reports about such attacks, manufacturing and
provisioning processes have gained much scrutiny and have improved.
Many different attacks have been reported as part of revelations
associated with pervasive surveillance.  Some of the reported attacks
involved compromising the smart card supply chain, such as attacking
SIM card manufacturers and operators in an effort to compromise
shared secrets stored on these cards.  Such attacks are conceivable,
for instance, during the manufacturing process of cards, or during
the transfer of cards and associated information to the operator.
Since the publication of reports about such attacks, manufacturing
and provisioning processes have gained much scrutiny and have
improved.
Introducing FS for EAP-AKA' can be achieved by using an Elliptic
Curve Diffie-Hellman (ECDH) exchange RFC7748.  In EAP-AKA' FS this
exchange is run in an ephemeral manner, i.e., both sides generate
temporary keys as specified in RFC7748.  This method is referred to
as ECDHE, where the last 'E' stands for Ephemeral.
The possibility of attacks against key storage offered in SIM or
other smart cards has been a known threat.  But as the discussion in
attacks shows, the likelihood of practically feasible attacks has
increased.  Many of these attacks can be best dealt with improved
processes, e.g., limiting the access to the key material within the
factory or personnel, etc.  But not all attacks can be entirely ruled
out for well-resourced adversaries, irrespective of what the
technical algorithms and protection measures are.
This extension can provide assistance in situations where there is a
danger of attacks against the key material on SIM cards by
adversaries that can not or who are unwilling to mount active attacks
against large number of sessions.  This extension is most useful when
used in a context where EAP keys are used without further mixing that
can provide Forward Secrecy.  For instance, when used with IKEv2
RFC7296, the session keys produced by IKEv2 have this property, so
better characteristics of EAP keys is not that useful.  However,
typical link layer usage of EAP does not involve running Diffie-
Hellman, so using EAP to authenticate access to a network is one
situation where the extension defined in this document can be
helpful.
The possibility of attacks against key storage offered in SIM or
other smart cards has been a known threat.  But as the discussion in
attacks shows, the likelihood of practically feasible attacks such as
breaches in the smart card supply chain has increased.  Many of these
attacks can be best dealt with improved processes, e.g., limiting the
access to the key material within the factory or personnel, etc.  But
not all attacks can be entirely ruled out for well-resourced
adversaries, irrespective of what the technical algorithms and
protection measures are.  Always assuming breach such as key
compromise and minimizing the impact of breach are essential zero-
trust principles.
If a mechanism without forward secrecy such as (5G-AKA, EAP-
AKAa&#128;&#153;) is used the effects of key compromise are
devastating.  The serious consequences of breach somewhere in the
supply chain or after delivery that are possible when 5G-AKA or EAP-
AKA' is used but not when something with forward secrecy like EAP-
AKA-FS is used are: 1.  A passive attacker can eavesdrop (decrypt)
all future 5G communication (control and user plane both directions),
previously recorded in the past (control and user plane both
directions), and 3.  An active attacker can impersonate UE and
Network and inject messages in an ongoing 5G connection between the
real UE and the real network (control and user plane both
directions).
Best practice security today is to mandate forward secrecy (as is
done in WPA3, EAP-TLS 1.3, EAP-TTLS 1.3, etc).  It is RECOMMENDED to
long term completely phase out AKA without FS.
This extension can provide assistance in situations where there is a
danger of attacks against the key material on SIM cards by
adversaries that cannot or who are unwilling to mount active attacks
against large number of sessions.  The extension also provides
protection against active attacks as they are forced to be a Man-In-
The-Middle (MITM) during the AKA run and subsequent communication
between the parties.  Without forward secrecy an an active attacker
that has compromised the long-term key can inject messages in an
connection betwen the real Peer and the real server without being a
man-in-the-middle.  This extension is most useful when used in a
context where EAP keys are used without further mixing that can
provide Forward Secrecy.  For instance, when used with IKEv2 RFC7296,
the session keys produced by IKEv2 have this property, so better
characteristics of EAP keys is not that useful.  However, typical
link layer usage of EAP does not involve running Diffie-Hellman, so
using EAP to authenticate access to a network is one situation where
the extension defined in this document can be helpful.
Using EAP-AKA' FS once provides forward secrecy.  Forward secrecy
limits the effect of key leakage in one direction (compromise of a
key at time T2 does not compromise some key at time T1 where T1 <
T2).  Protection in the other direction (compromise at time T1 does
not compromise keys at time T2) can be achieved by rerunning ECDHE
frequentle.  If a long-term authentication key has been compromised,
rerunning EAP-AKA' FS gives protection against passive attackers.
Using the terms in {{RFC7624}}, forward secrecy without rerunning
ECDHE does not stop an attacker from doing static key exfiltration.
Frequently rerunning EC(DHE) forces an attacker to do dynamic key
exfiltration (or content exfiltration).