??S 36

1
??. ?a?. ?. Ge?????d??
??S 36 ?sf??e?a ?p?????st???? S?st?µ?t?? Lectu
re 6
?p. ??. ?. ?apapa?a???t?? conpap_at_di.uoa.gr ??.
?a???? ??????? marias_at_mm.di.uoa.gr
2
?e??e??µe?a

• S?st?µata ?a? ???t?????a a??e?t???p???s??
• Kerberos
• Pretty Good Privacy (PGP)
• Simple PKI/SDSI ANSI X9.68
• Personal PKI

3
Kerberos

• ?? Kerberos pa???e? ?p??es?e? a??e?t???p???s??
  ???st? se d??t?a?? ?a? ?ata?eµ?µ??a pe??ß?????ta,
  ???s?µ?p????ta? µ?a ?µp?st? t??t? ??t?t?ta (TTP)
• TTP ap?te?e? t?? KDC
• ??apt?????e ap? t? Project Athena t?? MIT
• http//web.mit.edu/kerberos/www/
• ?as??eta? se a??????µ??? s?µµet?????
  ???pt????f?s??
• ???e?t???p??e? d?? µ???
• ????µe??? (Client 2 Server)
• ?µ??ßa?a (C 2 S/ S 2C)
• ????? ?a ap??a??pte? ????? µ?st??? (p.?.,
  password)
• ???s?µ?p??e? ?? ß?s? t?? a??????µ? Needham
  Schroeder.

4
Kerberos

• ???s?µ?p??e?ta?, µeta?? ?????, sta Windows 2000
  ??a t?? a??e?t???p???s? t?? ???st?? st? s?st?µa
  ?a? t? ???s? d??t?a??? p????
• ?? ????? µ?st??? e??a? ??a ??e?d? p?? ßas??eta?
  st? s????µat??? t?? ???st?
• ???s?µ?p??e?ta? ?a? ??a ?a ?p?st????e? efa?µ????
  Single Sign On (SSO)
• ?e?e?ta?a ??d?s? v5 (RFC 1510)
• H v4 ???s?µ?p??e?ta? a??µa, e?? ?? e?d?se?? 1-3
  de? d?µ?s?e?t??a?

5
???s?µ?t?ta

• ?? Kerberos a?t?µet?p??e? t? p??ß??µa t??
  a??e?t???p???s?? se ??a d??t?a?? pe??ß?????, ?p??
  d??f??e? ?p??es?e? pa?????ta? ap? a?e???t?ta
  s?st?µata ta ?p??a ep?????????? µeta?? t??? µ?s?
  d??t???
• ?? ?p??es?e? µp????? ?a pa?????ta? µ??? se
  ???ste? µet? ap? e???s??d?t?s?
• ?? Kerberos a?t??a??st? t?? a????? ep?µ?????
  a??e?t???p???s?? se ???e s?st?µa, µe ??a ?e?t????
  s?st?µa p?? d?a?e????eta? ??e? t?? s??se??
  eµp?st?s???? µeta?? ?p??es??? ?a? ???st??

6
?pa?t?se??

• ?sf??e?a ??a? ?ta???st?? de? ?a p??pe? ?a µp??e?
  ?a ???s?µ?p???se? t?? p????f???e? p?? ?aµß??e?
  ??a ?a ?d??p????e? t?? ta?t?t?ta e??? ???st?
• ????p?st?a ?f?s?? ? ??e???? p??sßas?? st??
  ?p??es?e? ???eta? ap? t? Kerberos, p??a?? ???e???
  d?a?es?µ?t?t?? t?? ?a s??ep??eta? ?a? µ?
  d?a?es?µ?t?ta t?? ?p??es???. S??ep?? ? Kerberos
  ?a p??pe? ?a e??a? p??ta d?a??s?µ??
• ???p??e?ta? µ?sa ap? µ?a ?ata?eµ?µ???
  a???te?t????? (?at? specs)
• ??af??e?a ? ???st?? de? ?a p??pe? ?a
  a?t??aµß??eta? t?? ?pa??? t?? s?st?µat?? e??????
  p??sp??as??, p??a ap? t?? apa?t?s? e?sa????? e???
  s????µat????.
• ???µ???s? ???pe? ?a µp??e? ?a ?p?st????e? µe????
  a???µ? clients ?a? servers,
• µ?sa ap? µ?a ?ata?eµ?µ??? a???te?t????? domains
  (realms)

7
??a??µ? ??e?d??? µ?s? TTP

• Se????? µe s?µµet???? ??e?d??
• ???t?? n ??µß??
• ???e ?e???? ??µß?? ???e? ?a ep????????se? µe
  asf??e?a
• ?pa?t???ta? n(n-1)/2 ??e?d?? ?a? ???e ??µß??
  p??pe? ?a d?a??te? n-1 ??e?d??
• Ta µp????sa? ?a ???s?µ?p??????? a??????µ??
  as?µµet??? ???pt???af?a?
• ??a??a?t???, ?a µp????se ?a ???s?µ?p????e? µ?a
  ?µp?st? t??t? ??t?t?ta (KDC) p?? ?a ß???? t???
  ???ste? ?a a??e?t???p?????ta? µ??? ap??a?t? t??
• ?at?p?? µ???????ta? ??e?d?? s???d?? (d???e?? 2?)
• ?e???? ???s? p??t??????? Needham - Schroeder

8
Needham Schroeder??e?d??

• ???e ??µß?? H µ?????eta? ??a ??e?d? µa????
  d????e?a? KH,T µe t? KDC, T.
• ? Alice µ?????eta? ??a ??e?d? µa???? d????e?a?
  KA,T µe t? KDC.
• ? Bob ep?s?? µ?????eta? ??a ??e?d? µa????
  d????e?a? KB,T µe t? KDC.
• ?????? ? Alice ?a? ? Bob de? µ???????ta? ??p???
  ????? ??e?d?.
• ? Alice ?a? ? Bob ???s?µ?p????? t? KDC ?ste ?a
  a??e?t???p?????ta? ? ??a? ap??a?t? st?? ?????
  (?µµesa) ?a? ?a s?µf???s??? se ??a ??e?d?
  s???d??.

9
Needham Schroeder?? p??t??????

• ???a??d??s? ?????? ??e?d??? s???d?? ? µeta??
  Alice ?a? Bob µ?s? ???
• A T A B NA
• T A ?KA,TNA B K ?KB,TK A
• A B ?KB,TK A
• B A NB
• A B ?KNB -1B

KDC
2
1
3
Alice
Bob
4
5
10
Needham Schroeder ??a??t???

• 1 ? Alice st???e? st? KDC ??a µ???µa p??
  pe????e? t? ???µa t??, t? ???µa t?? ?ob ?a? ??a
  t??a?? a???µ? (? a????ta)
• 2 ?? KDC d?µ?????e? ??a (?e?d?)t??a?? ??e?d?
  s???d??, t? ?p??? t? d??e? st?? Alice.
• St? st?d?? a?t? a??e?t???p??e?ta? ap??a?t? st??
  Alice.
• 3 H Alice st???e? t? ??e?d? s???d??
  ???pt???af?µ??? ap? KDC st?? Bob.
• 4 O Bob st???e? st?? Alice ??a t??a?? a???µ? (?
  a????ta)
• 5 ? ?lice a??e?t???p??e?ta? ap??a?t? st?? Bob
  ???s?µ?p????ta? t? ??e?d? s???d?? K p?? p????
  µp????? ?a? ?a µ???????ta?

11
??e??e?t?µata - ?e???e?t?µata

• ??e??e?t?µata
• ?pa?t???ta? µ??? n ??e?d?? st? KDC
• ?pa?te?ta? µ??? ??a ??e?d? µa???? d????e?a? st??
  ???e ??µß? (a?t? n-1)
• ???s? S?µµet????? ???pt???af?a?
• ? ?ob µp??e? ?a e??a? offline sta ß?µata 1 ?a? 2,
  ?µ???? ?a? o KDC sta ß?µata 3,4,5.
• ?e???e?t?µata
• KDC ???ad??? s?µe?? ?at???e?s??
• F??t?? µ???µ?t?? st? KDC
• ?pa?t?s? ??a ?µp?st? KDC
• ?pa?t?s? ??a ?a?? d?a?e???s? ??e?d??? µa????
  d?a??e?a? ap? t??? ??µß???

12
St???e?a t?? Kerberos

• Kerberos Key Distribution Centre (KDC)
• ???st? ?a? sa? Kerberos Authentication Server
  (KAS)
• a??e?t???p??e? ???ste? (? ?a? ???e? ??t?t?te?)
  ?a? e?d?de? e?s?t???a, ta ?p??a e??a? ?????a ??a
  µ?a s???d?
• Ticket Granting Servers (TGSs)
• ??d?d??? e?s?t???a p??? ??t?t?te? p?? ??t???
  p??sßas? se d??t?a??? ?p??es?e?
• Client
• ???ste? p?? ep???µ??? ?a ????? p??sßas? se
  ?p??es?e? p?? pa?????ta? ap? servers t?? d??t???
• Server
• ?a?????? ?p??es?e? se clients ßas???µe??? st??
  a??e?t???p???s? p?? p?a?µat?p????? ?? KDC ?a? TGS
• Realm
• To s????? t?? client ?a? server p?? d?a?e???st???
  a?????? se ??a ?e???? KDC/TGS

13
???t??????

1. ??t?s? ??a Ticket-Granting Ticket
2. Ticket-Granting Ticket
3. ??t?s? ??a Server Ticket
4. Server Ticket
5. ??t?s? ??a Service
6. ?sfa??? ep????????a

TGS (ticket- granting server)
KDC (Authentication Server, AS)
2
1
3
4
C (client)
S (server)
5
6
14
F?se?? t?? p??t???????

• F?s? 1 Sta µ???µata 1 ?a? 2, ???s?µ?p??e?ta? t?
  ??e?d? µa???? d????e?a? ??a a??e?t???p???s?
  µeta?? Client ?a? KDC. To KDC d??e? ??a ??e?d?
  µ????? d????e?a? ?a? ??a ticket granting ticket
  (TGT).
• F?s? 2 Sta µ???µata 3 ?a? 4, ???s?µ?p?????ta? t?
  ??e?d? µ????? d????e?a? ?a? t? TGT ??a
  a??e?t???p???s? µeta?? Client ?a? TGS. ? TGS
  d??e? ??a ??e?d? s???d?? ?a? ??a e?s?t????
  (ticket).
• F?s? 3 Sta µ???µata 5 ?a? 6, ???s?µ?p?????ta? t?
  ??e?d? s???d?? ?a? t? e?s?t???? ??a
  a??e?t???p???s? µeta?? Client ?a? Server ?a? ??a
  t?? e??a??d??s? asfa???? s???d??.
• ?? F?se?? 2 ?a? 3 s?????? epa?a?aµß????ta? p?????
  f???? ??a ???e 1? f?s?.

15
??? ????µ?t??
Network security essentials (International
edition), William Stallings, Prentice-Hall, 2002.
ISBN 0131202715
16
????µata

• Authentication phase
• ?p??t?s? Ticket-Granting Ticket (TGT)
• Once per user logon session
• 1. C?KDC IDtgsIDCTS1
• 2. KDC?C EKcKc,tgs IDtgs TS2 Lifetime2
  Tickettgs
• Tickettgs Ekkdc, tgsKc,tgs IDc ADc
  IDtgs TS2 Lifetime2

17
????µata

• Ticket Granting Service phase
• ?p??t?s? Service-Granting Ticket
• Once per type of service
• 3. C?TGS IDS TickettgsAuthenticatorc
• 4. TGS?C Ekc,tgsKc,s IDs TS4 Tickets
• Tickettgs Ekkdc, tgsKc,tgs IDc ADc
  IDtgs TS2 Lifetime2
• Tickets EksKc,s IDc ADc IDs
  TS4 Lifetime4
• Authenticatorc Ekc,tgsIDc ADc TS3

18
????µata

• Client-Server Authentication phase
• ???sßas? se ?p??es?a
• Once per service session
• 5. C?S TicketsAuthenticatorc
• 6. S?C Ekc, sTS5 1
• Tickets EksKc,s IDc ADc IDs
  TS4 Lifetime4
• Authenticatorc Ekc, sIDc ADc TS5

19
???e?t???p???s? se ??af??et??? Realms

• ?? Kerberos ?p?st????e? a??e?t???p???s? se
  d?af??et??? realms
• Clients p?? a?????? se ??a realms µp????? ?a
  ????? p??sßas? se servers ????? realm.
• ?pa?te?ta? p??-s?µf???a µeta?? t?? s?et????
  KDC/TGS.
• ???s?µ?p?????ta? forwardable tickets.
• ??a? Client st? realm A ??te? ??a TGT ap? t?? TGS
  ??a ?a t? ???s?µ?p???se? se ??a ???? realm B.
• ? TGS t?? realm A d??e? ??a TGT ??a t? realm B.
• ? TGS p??pe? ?a ??????e? t? ??e?d? KKDC,TGS p??
  ?s??e? st? realm B.
• ? TGS st? realm A e?s??e? ??a forwardable flag
  st? TGT p?? e?d?de?.
• ? Client ap? t? realm A µp??e? ?a ???s?µ?p???se?
  t? TGT st? realm B.

20
?p????????a ?eta?? Realms
Network security essentials (International
edition), William Stallings, Prentice-Hall, 2002.
ISBN 0131202715
21
??af???? v4 v5

• To v4 ???s?µ?p??e? DES e?? t? v5 µp??e? ?a
  ???s?µ?p???se? ?p????d?p?te a??????µ?.
• ?? v4 ßas??eta? st?? d?e????se?? t?? p??t???????
  IP e?? t? v5 µp??e? ?a ???s?µ?p???se?
  ?p??esd?p?te d?e????se??.
• ?a e?s?t???a st? v4 µp????? ?a e??a? µ???? 21
  ??e?, e?? st? v5 ????? s???e???µ????? ???????
  a???? ?a? t?????.
• ?a µ???µata 2 ?a? 4 ???pt???af???ta? 2 f???? st?
  v4.

22
?????t? T?µata

• ??????s? ?a TGT ?s????? µ???? ?a ??????, s??????
  se 10 ??e?.
• ??a?e???s? ??e?d??? µ?sa se ??a realm ??e?d??
  µa???? d?a??e?a? p??pe? ?a a?ta??a????? µeta??
  KDC ?a? TGS, TGS ?a? Server, KDC ?a? Client.
• ?pa?te?ta? s???????sµ?? t?? ????????, ef?s??
  ???s?µ?p?????ta? ???????? e?de??e??.
• ??a?es?µ?t?ta apa?t???ta? online ?µp?st?? KDC
  ?a? TGS.
• Key storage short-term keys ?a? ticket-granting
  tickets e??a? ap????e?µ??a se µ? p??state??µe????
  client hosts.
• S????µat??? st?? pe??ss?te?e? ???p???se?? t?
  ??e?d? µa???? d?a??e?a? µeta?? Client ?a? KDC
  (KKDC,C) ßas??eta? se ??a s????µat??? p?? e?s??e?
  ? ???st?? st?? a??? t?? s???d??
• ?p???se?? µe ???s? ?e????? e??a? d??at??
• p.?. http//citeseer.ist.psu.edu/wu99realworld.ht
  ml
• ?e???? ? asf??e?a t?? s?st?µat?? e?a?t?ta? ap?
  t??? ???ste? ?a? t?? p???t?ta t?? s????µat????.
• ??p??e?e? st?? ??d??a ???e t?s? ß??s???ta?
  a??et??
• http//web.mit.edu/kerberos/www/advisories/

23
Single Sign On (SSO)

• O Kerberos e??a? ??a pa??de??µa s?st?µat?? Single
  Sign On (SSO).
• ? ???st?? e?s??e? ??a µ??? s????µat??? ??a ?a
  ap??t?se? p??sßas? se p???ap??? ?p??es?e? ?a?
  efa?µ????.
• Microsoft Passport pa??de??µa web-based
  efa?µ???? SSO solution.
• Liberty Alliance µ?a a????t? p??sp??e?a
  d?µ??????a? p??t?p?? ??a t?? ep?te??? µ?a?
  federated network identity, ?????a? p??
  s?et??eta? µe t? SSO.

24
PGP - Pretty Good Privacy

• ?a???e? se µ???µata ?p??es?e?
• ???e?t???p???s?? t?? p???? p????e?s??
• Confidentiality
• Compression
• ?a???e? ?p??es?e? Key management
• Generation, distribution, revocation of
  public/private keys
• Generation distribution of session keys
• ?e? apa?te? t?? ?pa??? ?e?t????? ?????
  ??st?p???s?? (CA)
• ???e ??µß?? e??a? CA

25
PGP - Pretty Good Privacy

• ??apt?????e ap? t?? Phil Zimmermann t? 1991
  (first version)
• Commercial version by PGP Corp. www.pgp.com
• Freeware version www.pgpi.org
• OpenPGP RFC 2440
• www.ietf.org/html.charters/openpgp-charter.html
• ?? ?a? µp??e? ?a ???s?µ?p????e? ??a ?a
  ???pt???af?se? ?p??ad?p?te ded?µ??a,
  ???s?µ?p??e?ta? ?????? ??a e-mail
• ?p???e? e?s?µat?µ??? st??? pe??ss?te???? e-mail
  clients

26
???e?t???p???s?/ ???pt????f?s? st? PGP

• ???s?µ?p??e? s??d?asµ? as?µµet??? ?a? s?µµet?????
  ???pt???af?a?
• ? ap?st???a? ???pt???afe? ???s?µ?p????ta?
  s?µµet?????? a??????µ??? ?a? ??a ??e?d? s???d??
  t? µ???µa
• ?? ??e?d? s???d?? ???pt???afe?ta? µe t? d?µ?s??
  ??e?d? t?? pa?a??pt? ?a? ap?st???eta? µa?? µe t?
  µ???µa
• ? pa?a??pt?? ap????pt???afe? t? ??e?d? s???d??
  ???s?µ?p????ta? t? ?d??t??? t?? ??e?d?
• ?e t? ??e?d? s???d?? ap????pt???afe? t? µ???µa
• ?p?st?????µe??? a??????µ??
• S?µµet????? DES, 3DES, AES, ??p.
• ?s?µµet??? RSA, El Gamal, ??p.

27
???e?t???p???s?/ ???pt????f?s? st? PGP
??µ?s?? ??e?d? pa?a??pt?
?d??t??? ??e?d? pa?a??pt?
???pt???af?µ??? ??e?d? s???d??
??e?d? s???d??
??e?d? s???d??
?p????pt????f?s?
????µa
????µa
???pt????f?s?
???pt???af?µ??? µ???µa
28
??a?e???s? ??e?d???

• ???e ???st?? µp??e? ?a ??e? p???? ?e??? ??e?d???
  ?d??t???-d?µ?s??
• ta ?e??? ??e?d??? ap????e???ta? se ??e?d????e?
  (key rings)
• Private key ring
• ?p????e?e? ta ?e??? public private keys p??
  a?????? st?? ?d???t?t?
• Public key ring
• ?p????e?e? ta public keys p?? a?????? se ??????
  ???ste?
• ??s????e?
• ???? public key ?a p?st?p???se? µ?a ?p???af? ?
• ???? private key ?a ap????pt???af?se? t? session
  key ?
• ?et?d?s? ???? t?? public key e??a? spat???
• S?et????ta? ??a t??a?? ID st? public key p???a?e?
  d?a?e???st??? p??ß??µa
• PGP key ID least significant 64 bits t?? public
  key
• S?ed?? s?????a µ??ad??? ??a ??a ???st?
• DEADBEEF attack

29
??a?e???s? ??e?d???

• ???e ???st?? ??e? ??a p?st?p???t??? p??
  p?st?p??e? t?? a?t?st????a ???st?-d?µ?s???
  ??e?d???
• ??p??? ?????a ???st? ??? ?a?????? ?.500
• ?? p?st?p???t??? µp??e? ?a ?p?????e? ?p???sd?p?te
  t??t?? d??eta? t?? a?t?st????a a?t?
• ?p?????? d??f??e? d?aßa?µ?se?? eµp?st?s???? se
  a?t? t?? ?p???af?
• ?se? pe??ss?te?e? ?p???af?? µa?e?e?
• ???? t? µ??t??? eµp?st?s????

30
Web of Trust

• Owner Trust
• ?p?peda eµp?st?s???? p?? t??e?ta? ap? ???st?
• ???e ???st?? µp??e? ?a ap??t?se? µ?a ?
  pe??ss?te?e? ?p???af?? ??a t? p?st?p???t??? t??
• a????e? t?? a???p?st?a t??
• ??? ? ???st?? ? eµp?ste?eta? t? p?st?p???t??? t??
  ? ?a? ? ? eµp?ste?eta? t? p?st?p???t??? t?? G,
  t?te ? ? µp??e? ?a eµp?ste?te? t? p?st?p???t???
  t?? G
• ? a??s?da eµp?st?s???? µp??e? ?a e?a?t?ta? ap? t?
  ßa?µ? eµp?st?s???? se ???e p?st?p???t??? ?e????st?

31
Web of Trust

• Se ?e?te?e? e?d?se?? e?s??eta? ? ?????a t??
  ?p???af?? eµp?st?s???? p?? µp????? ?a
  ?p?st??????? t? d?µ??????a ????? ??st?p???s??
• ? ?p???af? eµp?st?s???? ep?ßeßa???e? t??
  a?t?st????a ??e?d???-??t?t?ta? ?a? d?aßeßa???e?
  p?? ? ?d???t?t?? t?? ??e?d??? e??a? a??et?
  ?µp?st?? ?a ?p????fe? ???a p?st?p???t???
• ??a µ??f? distributed CAs

32
??a??a?t???? ?p?d?µ?? ??µ?s??? ??e?d???

• ??f?a?? ??st?p???t???
• S??d???? ???µata µe ??e?d??
• ??µ?s?a ?µesa, ??a ?a? ?d??t??? ?µµesa
• ??µ?s?a d?a??s?µe? ??ste? p?st?p???t????
  d?µ???????? ??a t?p? t??ef?????? ?ata?????
• Kohnfelder (1978)
• ??? de? ?p???e? ?µes?? ?a? a???p?st?? t??p??
  d?aµ???asµ?? t?? ??e?d???, ?a??te?a ?a
  eµp?ste?t??µe ??p??a ?µp?st? t??t? ??t?t?ta

33
?a?????? ???µata

• ?.500 ?a? X.509
• Distinguished Name ??a pa???sµ?? ???µa p??
  ?a?a?t????e? µ??ad??? µ?a ??t?t?ta.
• ?????a ???p???s?µ? se µ????? ???????e?
• ???? e??a? ???st?? µe ta ???µat? t???
• ?? ef??t? se pa???sµ?a ???µa?a
• ?e? ?p???e? pa???sµ??? ?a???a? ???µat?d?s?a?
• ?????? eta???e? d?ast????p?????ta? st? ????,
  d????ta? ? ?a?eµ?a ???µata µe d?af??et??? t??p?

34
??st?p???t??? X.509
35
SPKI

• Simple PKI
• ???s?µ?p??e? t?p??? ???µata
• ?e? apa?te?ta? ?a e??a? ?a?????? µ??ad???
• ???pe? ?a e??a? µ??ad??? sta p?a?s?a t??
  ??t?t?ta? p?? ta d?a?e????eta?
• ??e??????e? t? d?µ??????a ??st?? e??????
  p??sßas?? (ACL Access Control Lists)

36
???µat?????a SDSI

• Simple Distributed Security Infrastructure
• ??apt?????e pa??????a µe t? SPKI, ?a? a???te?a
  e??p??????a?
• S?µf??a µe t? SDSI 2.0 ??a ßas??? ???µa
  ap?te?e?ta? ap? 2 st???e?a t? ???? name ?a? t?
  ???µa
• p.?.
• george (name fred)
• ? george o???e? t? ???µa fred
• S???eta ???µata
• fred (name sam)
• george (name fred sam)

37
??e???p???s? ???µ?t?? SDSI

• ??p??e? efa?µ???? apa?t??? pa???sµ??? µ??ad???
  ???µata
• St?? as?µµet?? ???pt???af?a ????µe ?d? ??a
  µ??ad??? ?a?a?t???st??? t? ?d??t??? ??e?d?
• ???e ?d??t??? ??e?d? s?et??eta? µ??ad??? µe t?
  a?t?st???? d?µ?s??
• ?p?????st??? ? s????? t?? d?µ?s??? ??e?d??? e??a?
  ep?s?? µ??ad???
• ??a ???µa SDSI pa???e? t? µ??f?
• (name (S???????e?d?????d?t?) ???µa)
• p.?. (name (TLCgPLFlGTzgUbcaYLW8kGTEnUk) jim)

38
??st?p???t??? SPKI

• ??st?p???t??? ???µ?t??
• ??st?p????? ?t? ??a ???µa a???e? st?? e?d?t? t??
  p?st?p???t????
• ?????? s?µß????? ???µata se ??e?d?? ? ?µ?de?
  ??e?d???
• C (K,A,S,V)
• K ?? d?µ?s?? ??e?d? t?? e?d?t?
• ? ??p??? ???µa
• S ???µa ? ??e?d? p?? p??sd?de? ep?p????
  ?a?a?t???st??? st? s???e???µ??? ???µa
• V ?????e?a ?s????
• ?? p?st?p???t??? ?p????feta? ??f?a?? ap? t??
  e?d?t?

39
??st?p???t??? SPKI (2)

• ??st?p???t??? ???e?t???p???s??
• ???e?t???p????? ??a ???st?
• ??t?st?????? s???e???µ??a d??a??µata se ??e?d?? ?
  ?µ?de? ??e?d???
• C (K,S,d,T,V)
• K ?? d?µ?s?? ??e?d? t?? e?d?t?, ? ?p????
  a??e?t???p??e? t?? ???st?
• S ?? ?p??e?µe?? p?? a??e?t???p??e?ta?
• d delegation bit ???e? d??a??µa µetaf???? t??
  s???e???µ???? d??a??µ?t?? ?a? se ???a ??e?d?? t??
  ?d??? ???st?
• T ???a??µata p?? d????ta?
• V ?????e?a ?s????

40
X9.68 Domain Certificates

• ANSI 2001
• Digital Certificates for Mobile/Wireless and High
  Transaction Volume Financial Systems
• ?????e? ??a PKI se domains
• ???s?µ?p??e? t?p??? ???µata sta domains
• ?at a?a????a µe SPKI
• ?p?ß???e? a?st????? s??ta?t????? ?a???e?
• pe??????e? t? µ??e??? t?? p?st?p???t???? ?a?
• ap???ste?se? t?? epe?e??as?a t???

41
X.509 vs X9.68

• X.509 ??a p?st?p???t??? pe???aµß??e?
• ???µa e?d?t? (distinguished name)
• Se???a??? ????µ??
• ???µa ?at???? (distinguished name)
• X9.68 ?a pa?ap??? a?t??a??sta?ta? ap? d?? ped?a
• rootName ?a?????e? t?? ?d???t?t? t??
  p?st?p???t???? ???a? t?? domain
• localName ??sta ???µ?t?? p?? s??µat????? µ?a
  ?e?a???a, ?p?? ta s???eta ???µata SDSI.
• ?? de???te?? ???µa e??a? t? ???µa t?? ?at????
• ??e??e?t?µata X9.68
• ?????te?? µ??e??? epe?d? de ???s?µ?p?????ta? DNs
• ??????a st? d?µ??????a t?? a??s?da? eµp?st?s????

42
Personal PKI

• ???t?a ???s?p???? ?p?????????? (Personal Area
  Networks PAN)
• ?? ???ste? t??? de? ????? t??p?
• ?a a?ta??????? µ?st??? s?µµet???? ??e?d??
• ?a p??µ??e?t??? d?µ?s?a ??e?d?? ap? µ?a ?e?t????
  ?p?d?µ? PKI
• ?p??e? ?a ???p????e? µ?a pe?????sµ??? ?p?d?µ? PKI
• Te????µe ?t? ??a? ??µß?? ?e?t????e? sa? Personal
  CA
• O Personal CA e?d?de? p?st?p???t??? ??a ?????
  t??? ???ste? t?? d??t???

43
???ß??µata st? Personal PKI

• ??a???s? ??st?p???t???? ?a? ??e?d???
• ?ta? pa????e? ? ?µe??µ???a ????? t??
  p?st?p???t???? a?t? p??pe? ?a a?a?e??e?
• ??????s? ??st?p???t????
• ?? ?d??t??? ??e?d? e??? ???st? µp??e? ?a ??ape?
• ?? ?d??t??? ??e?d? t?? Personal CA µp??e? ?a
  ??ape?
• Se ???e pe??pt?s? ???? ?? ???ste? t?? d??t???
  p??pe? ?a e??µe??????
• ??a?e???s? eµp?st?s????
• ? Personal CA p??pe? ?a e??a? ?a?????? ?µp?st?
• ???pe? ?a ?p?st????eta? ? a?a???s? ??e?d??? t??
  Personal CA
• ? s?s?e?? p?? e?te?e? ???? Personal CA µp??e? ?a
  ??ape? ? ?a ?a?e?

44
???p???s?

• ???t?????? a?ta??a??? d?µ?s??? ??e?d??? ??a t??
  ??d?s? p?st?p???t???? ???st??.
• ?pa?te? f?s??? epaf? ???st?-Personal CA ??a ?a
  e?s??e? ??a a?a?????st??? t?? s?s?e???
• ? Personal CA s?????e? ??a ta d?µ?s?a
  ??e?d??-p?st?p???t??? t?? ???st??. ????? ??p???
  ???e? e??µe???e? t?? ???st? ?a? e?d?de? ??? a?
  ??t? t?t??? apa?te?ta?
• ??????s? p?st?p???t????
• ????µ?? online Personal CA OCSP
• ?at? pe???d??? offline CA pe???d????
  d?aµ???asµ?? CRLs
• ??a???s? ??e?d??? ???a?
• ??aµ???asµ?? ???? p?st?p???t???? ???a?
  ?p??e??aµµ??? µe t? pa??? ??e?d?
• Se pe??pt?s? ???p??
• ???s? p???ap??? Personal CA
• ?p????? ??a? Personal CA

45
?pa?t?se??

• ?? ?e???? ??e?d??? t?? Personal CA p??pe? ?a ??e?
  d?µ???????e? st? s?s?e?? ? ?a ??e? t?p??et??e? µe
  asf??e?a st? s?s?e?? ?at? t?? ?atas?e?? t??
• ? pa?a???????s? ap? t??t??? t?? µ???µ?t?? p??
  a?ta???ss??ta? de ?a p??pe? ?a ?d??e? st??
  ap??????? µ?st???? p????f???a?
• ?a???a? ?ta???st?? de ?a p??pe? ?a µp??e? ?a
  t??p?p???se? ta µ???µata µeta?? ??µß?? ?a?
  Personal CA µe t??p? t?t???, ?ste ?a d?µ???????e?
  ??a p?st?p???t??? ??a ?a??asµ??? s?s?e??, ? ?a
  pe????e? µ? ?????a st???e?a (p.?. d?af??et???
  d?µ?s?? ??e?d?)
• ? ep????????a p?? ??e???eta? ??a ?a µetad??e? t?
  root certificate t?? Personal CA st??? ??µß???
  t?? d??t??? ?a p??state?eta? t??????st?? ap? ??a
  as?e??? ????? µ?st??? (p.?. ??a password ?
  PIN). ? µ???d?? p?? ?a ???s?µ?p??e?ta? ??a t?
  s??p? a?t? ?a p??pe? ?a e??a? a??e?t??? se
  ep???se?? t?p?? brute force