??S36

1
??S36 ?sf??e?a ?????f???a??? S?st?µ?t??
??. ?a?. ?. Ge?????d?? ??. ?a???? ??????? ?p. ??.
?apapa?a???t?? ???sta?t????
06/06/07
2
??st?p???t???
??st?p???t???

• ?a?a?t???st??? p?st?p???t???? p?? pa?????ta? ap?
  CA
• ??st?p??e? t? d?µ?s?? ??e?d? t?? ??t?t?ta? p??
  ?at??e? t? a?t?st???? ?d??t??? ??e?d?
• ?aµ?a a????? ??a p??stas?a p?st?p???t????
• ???e ???st?? µe p??sßas? st? d?µ?s?? ??e?d? t??
  CA (KUaut) µp??e? ?a a?a?t?se? t? d?µ?s?? ??e?d?
  t?? ???st? p?? s??a???sseta?
• ???pt???afe?
• ???e?t???p??e?
• ?aµ?a ??t?t?ta, p??? t?? CA, de? ??e? t?
  d??at?t?ta ?a t??p?p???se? ??a p?st?p???t???
  ????? a?t? ?a µ? ???eta? a?t???pt?.
• ??a? ???st?? µp??e? ?a ??e? p???? t?? e???
  p?st?p???t??? (??a ??a ???e ?e???? KUA , KRA)

3
??st?p???t???
????? CA

• S?s??t?s? ??t?t?ta? µe Public Key.
• ???e?t???p??e? t?? ??t?t?ta p?? ?at??e? t?
  d?µ?s?? ??e?d? ..... ?a? ?t? ?at??e? t?
  a?t?st???? ?d??t???
• ???ß??µa ?e???? ?????t?ta ???st??
• ? CA µp??e? ?a ap?te??se? bottleneck
• ??s? ????ap??? CA
• ???e µ?a pa???e? p?st?p???t??? ??a ??a tµ?µa t??
  ?????t?ta?
• ??e????t?µa ??a?t? µ?a? Authority
• ??? p??ß??µa
• ???ste? µe p?st?p???t??? ap? d?af??et???? CA

4
??st?p???t???
??ap?st?p???s?
CAX
CAY
KUB
KUA
CB EKRyKUB , IDB, Time2
CA EKRxKUA , IDA, Time1
A
B
CA
CB
A a???t?se certificate ap? CA ?. B a???t?se
certificate ap? CA ?. ?? ? A de? ??????e? t?
public key t?? ?, t?? e??a? ????st? t?
certificate t?? B. ?? ? ? de? ??????e? t?
public key t?? ?, t?? e??a? ????st? t?
certificate t?? ?.
5
??st?p???t???
??ap?st?p???s?
KU?
C? EKRyKU? , ID?, Time3 C? EKRxKU? , ID?,
Time4
CAX
CAY
C?
KUB
CY
KUA
KU?
CB EKRyKUB , IDB, Time2
CA EKRxKUA , IDA, Time1
A
B
CA
CB
? A ??????e? t? public key t?? X ? A µp??e? ?a
a?a?t?se? t? certificate t?? ? (CY) signed by X O
A µp??e? ?a a?a?t?se? t? d?µ?s?? ??e?d? t?? Y p??
pe????eta? st? p?st?p???t??? CY O A d?a??te? t?
p?st?p???t??? t?? B (CB, issued by ?) ??a µp??e?
?a a?a?t?se? t? d?µ?s?? ??e?d? t?? ?.
??a-p?st?p???s? CAs ?? CAs a?ta???ss??? ta public
keys t??? ???e CA p?st?p??e? to public key t??
????? C?
6
??st?p???t???
??ap?st?p???s?
KU?
C? EKRyKU? , ID?, Time3 C? EKRxKU? , ID?,
Time4
CAX
CAY
C?
KUB
CY
KUA
KU?
CB EKRyKUB , IDB, Time2
CA EKRxKUA , IDA, Time1
A
B
CA
CB
Se????? ? ? p??pe? ?a ???pt???af?se? µ???µa ?
p??? ? ..... DKUxCY à DKUxEKRxKU? , ID?,
Time4 à KU? , ID?, Time4 DKUyCB à
DKUyEKRyKUB , IDB, Time2 à KUB , IDB,
Time2 C MKUB mod n
7
??st?p???t???
??ap?st?p???s?

• St?? pe??pt?s? a??µe???? p???ap??? CAs ?
  ??t?t?ta p?? ???e? ?a ep?????se? t?? e?????t?ta
  µ?a? ??f?a??? ?p???af?? ep???µe? t?? ap??t?s?
  e??? a??e?t???p???µ???? d?µ?s??? ??e?d???
  ep?????µ???? µ?s? e??? p?st?p???t????
  ?p??e??aµµ???? ap? µ?a CA d?af??et??? ap? a?t?
  p?? ??e? a????? s?µß???e?
• ?ts? µ?a a??s?da ap? p?st?p???t??? (certificate
  chain) ?a p??pe? ?a pa?as?e?e? st?? ??t?t?ta p??
  ep???µe? ep?????s? d?µ?s??? ??e?d???.
• ? a??s?da a?t?st???e? se ??a µ???p?t?
  eµp?st?s???? p?? ?e???? ap? t?? CA µe t?? ?p??a ?
  ??t?t?ta ??e? a????? s?µß???e? ?a? ?ata???e? st?
  d?µ?s?? ??e?d? t?? ?p???? ? e?????t?ta p??pe? ?a
  ep??????e?
• St???? a?e??es? e??? ?ate????t???? µ???pat???
  p?? ?e???? ap? t?? ??µß? p?? a?t?st???e? st?? CA
  t?? ?p??a ? ??t?t?ta eµp?ste?eta? a priori ?a?
  ?ata???e? st?? CA p?? ??e? ?p?????e? t?
  p?st?p???t??? p?? pe???aµß??e? t? d?µ?s?? ??e?d?
  t?? ?p???? ? e?????t?ta ep???t?te ?a ep??????e?

8
??st?p???t???
??ap?st?p???s?. ??µe???

• ?ltlt?gtgt t? p?st?p???t??? t?? ? p?? e?d?deta? ap?
  t? CA ?
• YltltBgtgt t? p?st?p???t??? t?? B p?? e?d?deta? ap?
  t? CA Y
• ? ???st?? ? (? ?) µp??e? ?a ???s?µ?p???se? µ?a
  a??s?da d?a-p?st?p???s?? ??a ?a a?a?t?se? t?
  d?µ?s?? ??e?d? t?? ? (? ?).
• S?µe????af???
• ? d?µ?s?? ??e?d? t?? ? Xltlt?gtgt?ltltBgtgt
• ? d?µ?s?? ??e?d? t?? ? ?ltlt?gtgt?ltlt?gtgt

?
?
?
B
???s?da p?st?p???s??
9
??st?p???t???
??ap?st?p???s?. ?ata?eµ?µ???
??t?t?ta ?, ??t???? p?st?p???t???? µe ?UA (??e?
e?d??e? ap? CA5) ??t?t?ta ?, ??t????
p?st?p???t???? µe ?U? (??e? e?d??e? ap? CA3) H B
st???e? st?? ? ??a ??f?a?? ?p??e??aµµ??? µ???µa
!!! ? ? ep???µe? ?a ap??t?se? eµp?st?s??? st?
d?µ?s?? ??e?d? ?UB t?? ??t?t?ta? ? ??
?ate?????µe?? µ???p?t? CA5, CA4, CA3 ?p???e? ?
a??s?da CA5ltltCA4gtgtCA4ltltCA3gtgt ?a? ? eµp?st?s???
st?? CA5 a??e? ??a t?? ? ? ? ???s?µ?p??e? t?
?U5 ?a? e???e? ep?????µ??? a?t???af? t?? ?U4 ap?
CA5ltltCA4gtgt ? ? ???s?µ?p??e? t? ?U4 ?a? e???e?
ep?????µ??? a?t???af? t?? ?U3 ap? CA4ltltCA3gtgt ?
? ???s?µ?p??e? t? ?U3 ??a ?a ep?????se? t??
a??e?t???t?ta t?? p?st?p???t???? p?? pe????e? t?
?UB
CA5
CA3
?
CA4
CA1
CA2
?
??af??eta? ?a? mesh-organized. St? ?sf??e?a
???t??? ?p?????st??, S. G???t?a???, S. ??ts??a?,
?. G???t?a???, a?af??eta? ?? µ??t???
eµp?st?s???? p??sa?at???sµ???? ???f??. ??
pa??de??µa e??a? ap? t? s????aµµa, ?ef. 3.8.2
10
??st?p???t???
??ap?st?p???s?. ?ata?eµ?µ???
( ) ??s????a st?? a?e??es? a??s?d?? ??a large
scale d??t?a eµp?st?s???? ( ) ???ß??µata t?p??
??? ( ) ??a??a?t??? t? s??µa ???? µe ?????
(Full Mesh topology) p?e????e? se
d?a-p?st?p???se?? Fully distributed à PGP Web
of Trust ? eµp?st?s??? ?t??eta? e?-a???? ?aµ?a
public key authority, ? Root CA ???e ??t?t?ta
e??a? µ?a CA n-1 certificates a??
??t?t?ta n(n-1) / 2 certificates st?
s????? ???e ??t?t?ta a?t?-?p????fe?t?
certificate t??
CA5
CA3
?
CA4
CA1
CA2
?
11
??st?p???t???
??ap?st?p???s?. ?e?a?????
? Root CA (UoA) ?p????fe? t? p?st?p???t??? t?? CA
School of Science H CA School of Science
?p????fe? t? p?st?p???t??? t?? CA di.uoa H CA
di.uoa ?p????fe? t? p?st?p???t??? t?? ??t?t?ta?
di.E1. Ost?s?, ? ??t?t?ta di.E1 ???s?µ?p??e? t?
d?µ?s?? ??e?d? t?? Root CA (UoA) ??a ?a
ep???t?se? t?? e?????t?ta d?µ?s??? ??e?d??? ?????
Ei st?? ?e?a???a ? root CA a?t?-?p????fe? t?
p?st?p???t??? t?? (self-signed) ( ) H
a???p?st?a e?a?t?ta? ap? t? ?d??t??? ??e?d? t??
Root CA ( ) ?a???s?e?e?? a??s?de?
p?st?p???s?? se µe???e? ?e?a???e?
Root CA
UoA
School of Science
School of Health
di.uoa
stat.uoa
doc.uoa
nurs.uoa
di.EN
di.E1
12
??st?p???t???
??ap?st?p???s?. ?e?a?????
Certs ap? CA
Trust Anchor
CD1EKRCAKUD1 , IDD1 CD2 EKRCAKUD2 ,
IDD2 CD3EKRCAKUD3 , IDD3 CD4EKRCAKUD4 ,
IDD4
??? ? root CA ?e?t????e? ?? trust anchor ?2 à ?1
?p??e??aµµ??? µ???µa ? ?2 à ?1 EKRA2M
IDA2 IDA2 D1 ?1 a?a??t? d?µ?s?? ??e?d?
?2 ?1 a?as??e? p?st?p???t??? CA2 To CA2
?p??e??aµµ??? ap? ?d??t??? ??e?d? D1 ?1 a?a??t?
d?µ?s?? ??e?d? D1 A1 a?as??e? p?st?p???t??? CD1
To CD1 ?p??e??aµµ??? ap? ?d??t??? ??e?d? root CA
t?? ?p??a ???? eµp?ste???ta?
CA
D1
D2
D4
D3
A2
A1
B2
B1
Certs ap? D1 CA1EKRD1KUA1 , IDA1 CA2
EKRD1KUA2 , IDA2
13
??st?p???t???
??ap?st?p???s?. ???d?a p???ap??? ?????
?? d?? Root CAs d?µ???????? p?st?p???t??? ? µ?a
??a t?? ????
KUUoA
CUoA
CUoA EKRUoCKUUoA , IDUoA CUoC EKRUoAKUUoC ,
IDUoC
CUoC
KUUoC
?? ???ste? p?? a?????? st?? ?e?a???a µe Root CA
t? UoA ap??t??? eµp?st?s??? sta p?st?p???t??? t??
?e?a???a? µe Root CA t? AUEB, ?a? ta??pa???.
14
??st?p???t???
??ap?st?p???s?. ?e?a???a µe a?t?st??fa
p?st?p???t???
?µ???t?te? µe a?st??? ?e?a????? ??af??? ???e
CA µp??e? ?a d?µ??????se? p?st?p???t??? ??a
???e? CAs ?µp??s??a p?st?p???t??? ??st?p???t???
t?? CAx, p?? d?µ????????ta? ap? CA p?? ß??s?eta?
??a ?e?a????? ep?ped? p?? p??? ap? t?? CAx.
(p.?., p?st?p???t??? t?? CA4 ap? CA5) ???st??fa
p?st?p???t??? ??st?p???t??? t?? CAx, p??
d?µ????????ta? ap? CA p?? ß??s?eta? ??a ?e?a?????
ep?ped? p?? ??t? ap? t?? CAx. (p.?.,
??st?p???t??? t?? CA3 ap? t? CA2) ???e ??t?t?ta
a?a??t? t? d?µ?s?? ??e?d? t?? CA p?? d?µ??????se
t? d??? t?? p?st?p???t??? ( ) H a???p?st?a de?
e?a?t?ta? µ??? t? ?d??t??? ??e?d? t?? Root CA (
) ?a???s?e?e?? a??s?de? p?st?p???s?? se µe???e?
?e?a???e? ???s? µ??t???? S?st??eta? st?
?509 ?ß??d??? ?e?a???a µe a?t?st??fa
p?st?p???t??? ?a? ???d?a p???ap??? ?????
CA5
CA3
CA4
CA1
CA2
15
??st?p???t???
??ap?st?p???s?. Bridge CA (U.S.)
FBCA G?f??a eµp?st?s????. ?a???e? a??s?de?
p?st?p???s?? µeta?? d?af??et???? trust domains
Principal CA ??a CA se ??a trust domain p??
d?a-p?st?p??e?ta? µe t?? FBCA. ???e trust domain
??e? µ?a principal CA. (se ?e?a????? d?µ? e??a? ?
Root CA, se mesh-organized µp??e? ?a e??a? ?p??a
CA). Peer CA Se mesh trust domain ? peer CA
??e? ??a self-signed certificate p?? d?a??µeta?
se ?at????? t?? p?st?p???t???? ??a ?a
d?µ??????s??? certification paths. Peer CAs
d?ap?st?p?????ta? µe ???e? CAs st? trust
domain. Root CA Se ?e?a????? trust domain, ?
root CA e??a? ? CA p?? a?????p??e? ??e? t??
a??s?de? p?st?p???s??. ?? ??t???? p?st?p???t????
ef?d?????ta? µe t? self-signed root CA certificate
Federal Bridge Certificate Authority
16
??st?p???t???
??ap?st?p???s?. Bridge CA (U.S.)

• Federal Bridge CA
• S?ed??st??e ??a ?a d?µ??????se? µ???p?t?a
  eµp?st?s???? se ?e????st? trust domains
• ???a? non-hierarchical CA
• ?e? e?d?de? p?st?p???t??? se ???e? CAs ?
  ??t?t?te?
• ?e? ?e?t????e? ?? Root CA
• ??ap?st?p??e?ta? µe Principal CA ?a? µ???.S
• ???e trust domain cross-certifies µe t?? FBCA
• ?ts? d?µ????????ta? certification paths µeta??
  ?p????d?p?te trust domains.
• O a???µ?? t?? cross-certificates p?? apa?t???ta?
  e??a? 2x, ?p?? x e??a? ? a???µ?? t?? trusted
  domains

Federal Bridge Certificate Authority
17
??st?p???t???
??ap?st?p???s?.
Trust Models and Management in Public-Key
Infrastructures, John Linn RSA Laboratories 6
November 2000
18
??st?p???t???
??ap?st?p???s?. ??a?efa?a??s?

• ?a p?st?p???t??? de? µp????? ?a p?ast???af?????.
  
• ??t??eta, µp????? ?a t?p??et????? se public
  directory
• ?? ?at?????? de? e??a? ?pe?????? ??a d?µ??????a
  p?st?p???t????, ap?? ta ap????e???? (µa?? µe ta
  ?a?a?t???st??? t?? p?e??da?)
• ???e p?st?p???t??? pe????e? t? d?µ?s?? ??e?d?
  t?? ???st? ?p??e??aµµ??? ap? t? ?d??t??? ??e?d?
  t?? CA p?? t? d?at??e?
• ??d?t??a CA d?µ?????e? ?a? ?p????fe? t?
  p?st?p???t???

19
????te?t?????? ??st?p???s??
??p?? p?st?p???t????
??p?? ??st?p???t???? ?a?a?t???st??? ?ed?? a?a?????s?? p?st?p???t????
?.509 (PKIX) ?e?a????? eµp?st?s??? ??t?st?????e? d?µ?s?a ??e?d?? µe ???µata ???µata ?????µe????? eµß??e?a? ??a-p?st?p???s? ?????µe???? µ??ad???, X500 Object Identifier
Simple Public Key Infrastructure (SPKI) ??t???µ? a??? p?st?p???s?? ???µata t?p???? eµß??e?a? ??µ?s?? ??e?d?
PGP ????µa eµp?st?s???? ? eµp?st?s??? ?? p??? t?? a???ße?a t?? pe??e??µ???? e??? p?st?p???t???? a????e? ?a ed?a???eta? a? ?? ???ste? ?p????f??? ta p?st?p???t??? t?? ????? ????ap??? a??s?de? p?st?p???s?? Self-signed ?p???af? p??s?p???? p?st?p???t???? E-mail address ?????µe???? µ??ad??? a??? µ? sta?e??
?sf??e?a ???t??? ?p?????st??, S. G???t?a???, S.
??ts??a?, ?. G???t?a???,
20
????te?t?????? ??st?p???s??
?.509 ??st?p???t???

• ITU-T recommendation X.509 (IETF PKIX)
• ISO 94952 t? a?t?st???? ISO standard
• St?????µe?? se ???pt???af?a d?µ?s??? ??e?d???
  ?a? p?st?p???t??? d?µ?s??? ??e?d???
• S??µa p?? ap?te?e?ta? ap? ??a s????? CA Servers
  µe ?ata??????
• ta?t?t?t?? ???st??, d?µ?s??? ??e?d???,
  p?st?p???t????, ?????s?µ??se??
• ?? te????? ???ste? (?p??e?µe?a) de? µp????? ?a
  e??a? CAs
• ?e?a????? ? d?µe??? d?ap?st?p???s?
• ?? RSA s?st??eta? ??a ???s? de? ep?ß???eta?
• ?fa?µ???? S/MIME, TLS/SSL, IPsec, SET

21
????te?t?????? ??st?p???s??
?.509 ??µ? ??st?p???t????

• ?a ITU-T recommendations (X.500 Series)
  p??sd???????? µ?a ?e?a????? d?µ? p??sd????sµ??
  a?t??e?µ????
• ?a???sµ?a? ?µß??e?a?

Root
CGR
CUS
CGB
OUoA
??a ?509 Distinguished Name (DN) CGR OUoA
OUDept. Of. Informatics CN J. Marias
OUDept. Of. Informatics
CNJ. Marias
22
????te?t?????? ??st?p???s??
?.509 ??µ? ??st?p???t????
v1, v2, v3
????a???, µ??ad???? ??a t?? e?d?t??a CA
???????µ?? (p.?., RSA, DSS, ECC) p??
???s?µ?p??e?ta? ??a ?p???af? t?? p?st?p???t????
ap? t?? CA (repeated)
???µa t?? e?d?t??a? CA (?at? X509 notation)
?e???d?? ?s???
???µa t?? ??t?t?ta? (X509 notation) ??a t?? ?p??a
e?d?deta? t? p?st.
?? d?µ?s?? ??e?d? t?? ??t?t?ta? ??a t?? ?p??a
e?d?deta? t? p?st?p???t???, ? a??????µ?? ??a
???s?
??a bit string p?? ???s?µ?p??e?ta? ??a ?a
p??sd????se? µ??ad??? t? CA ?a? t?? ???st? a? t?
t? ???µ? t??? ???s?µ?p??e?ta? ?a??
?p???af? ap? CA. ?f??? ??a ta ped?a. ?p????fe? t?
s????? ?a? pe????e? t?? a??????µ? p??
???s?µ?p??e?ta? ??a ?p???af? t?? p?st?p???t????
Network security essentials (International
edition), William Stallings, Prentice-Hall, 2002.
ISBN 0131202715
23
????te?t?????? ??st?p???s??
?.509 S?µe????af?a
???sµ?? ??st?p???t???? ?at? ?.509 ltltAgtgt CA
V, SN, AI, CA, TA, A, Ap ?ltlt?gtgt t?
p?st?p???t??? t?? ??t?t?ta? ? p?? e?d?deta? ap?
t? CA ? ?I ? ?p???af? t?? I ap? t?? ?.
?µpe????e? t? ? ?a? t?? ep?s??apt?µe??
???pt???af?µ??? ap? t?? X s????? V à Version SN
à Sequence Number AI à Algorithm Identifier CA à
??d?t??a ???? (?at? ?500) TA à ?????? e?????t?ta?
p?st?p???t???? ??a ? ? à ? ??t?t?ta A p??
p?st?p??e?ta? (subject) Ap à KUA, Public Key of A
24
????te?t?????? ??st?p???s??
?.509 ??st?p???t???
Version v3 Serial Number 0241000016Signat
ure Algorithm MD5 With RSA EncryptionIssuer
CNUoACA, OUDept. Of. Informatics, O UoA,
CGR Validity    Not Before Fri Dec 5
183901 2005    Not After Sat Dec 5 183901
2006Subject CNJ. Marias, OUDept. Of.
Informatics, O UoA, CGRSubject Public Key
Info Algorithm RSA Encryption Public
Key Modulus 00c2290163a1fe32ae0c518d
e9076b02feec6d0ecc954bdc0a4b0b31a
31ae1 681fd80bb791fbf7fdbd32ba7601
45e17f8b66cd7e79678d48302a09484c9
bc798d2b31ce9542c3c0a10b076ae0669
58ace8d84f3783c3f134026d9f38606f5e
544f71c79228fb0ab344f31aa3fe99f43
fd312e2f83b036533889b67c7de882390
2b  Public Exponent 65537 Extensions     Cert
ified Usage SSL ClientSignature AlgorithmMD5
With RSA Encryption Signature2d763f495b533
ac50206a3676dd90350577fdea7a9cd69
02976f666a7f95ea89757afcb02681fc33
bb60e8f7737737f88a043bfcc13e42403
d5816177e47351c735aab7233c3f52bc6
ebb5395282c63ee138c6398beee39fb3b9
29420d11a579af6d3af8a6bad09c55480
d7591050b47679832f32d2e49ed22ab28
e8d696a19b
25
????te?t?????? ??st?p???s??
?.509 S?µe????af?a

• ? ???st?? ? (? ?) µp??e? ?a ???s?µ?p???se? µ?a
  a??s?da d?a-p?st?p???s?? ??a ?a a?a?t?se? t?
  d?µ?s?? ??e?d? t?? ? (? ?).
• S?µe????af???
• ? a?a?t? d?µ?s?? ??e?d? ? Xltlt?gtgt?ltltBgtgt
• ? a?a?t? d?µ?s?? ??e?d? ? ?ltlt?gtgt?ltlt?gtgt
• ? a??s?da µp??e? ?a ap?te?e?ta? ap? ?p???d?p?te
  µe???? a???µ? d?ap?st?p???µ???? CAs
• X1ltlt?2gtgt?2ltltX3gtgt XNltltBgtgt
• ?d? ???e ?e???? CAs t?? a??s?da? (?i ,?i1) ?a
  p??pe? ?a d?ap?st?p????e?

?
?
?
B
26
????te?t?????? ??st?p???s??
?.509 ?e?a???a
?at?????? d?a-p?st?p???t???? p?? d?at?????ta? ap?
t?? ??t?t?ta
???s?de? ??st?p???s?? A a?a?t? t? p?st?p???t???
t?? B µ?s? t?? a??s?da? XltltWgtgtWltltVgtgtVltltYgtgtYltltZgt
gtZltltBgtgt ?ts? ap??t? p??sßas? se ??a trusted copy
t?? KUB. B a?a?t? t? p?st?p???t??? t?? A µ?s?
t?? a??s?da? ZltltYgtgtYltltVgtgtVltltWgtgtWltltXgtgtXltltAgtgt
?ts? ap??t? p??sßas? se ??a trusted copy t?? KUA.
Network security essentials (International
edition), William Stallings, Prentice-Hall, 2002.
ISBN 0131202715
27
????te?t?????? ??st?p???s??
?.509 ??????s? ??st?p???t????
G?at? a?????s? ???e p?st?p???t??? ??e? ???sµ??a
?a?a?t???st???, ?p?? pe???d?? ?s??? p?? e??a?
µetaßa???µe?a s?? t? ????? ????? ??????s?? ????
e??? p?st?p???t???? t??p?p???s? ?a?a?t???st????
??t?t?ta? (p.?., ???µa ? ta?t?t?ta) ??a t?? ?p??a
e?d?deta? t? p?st?p???t??? pa?aß?as? (?p????p?)
t?? ?d??t???? ??e?d??? µ?a? ??t?t?ta? (CA ?
te????? ???st??) ???? s?µßas?? ??t?t?ta? µe
CA pa?aß?as? (?p????p?) t?? ?d??t???? ??e?d???
t?? e?d?t??a? CA ???e CA d?at??e? µ?a ??sta
a?????s?? p?st?p???t???? ?p??e??aµµ??? ap? a?t?
G?a ??t?t?te? ? ???e? CA ?e???d??? d?µ?s?e?s? se
d?µ?s?a d?a??s?µ? ?at?????
28
????te?t?????? ??st?p???s??
?.509 ??????s? ??st?p???t???? Certificate
Revocation Lists

• ??sta a?a??????t?? p?st?p???t????
• Black-list
• ?pa?t? st?? a????? ??a epa???e?s? e?????t?ta?
  p?st?p???t????
• ??d?deta? ?a? ?p????feta? ap? CA
• p?? ??e? e?d?se? ?a? ?p?????e? ta a?t?st???a
  p?st?p???t???
• ??te???
• ?e????e?e? ??a ta p?st?p???t??? p?? ?????
  a?a????e? (ap? t? p??t? a?a?a???µe?? ...)
• ??af????ta? ?? ?µe??µ???e? ??d?s?? ?a? ep?µe???
  ??d?s??
• ?e???d??? ? Event-driven ??d?s?
• S??µa ??? request-response

29
????te?t?????? ??st?p???s??
?.509 ??????s? ??st?p???t???? Certificate
Revocation Lists
???????µ?? (p.?., RSA, DSS, EC) p??
???s?µ?p??e?ta? ??a ?p???af? ap? t?? CA (repeated)
???µa t?? e?d?t??a? CA (?at? X509 notation)
?µe??µ???a ??d?s?? CRL
?µe??µ???a ??d?s?? ep?µe??? CRL
????a???, µ??ad???? ??a t?? e?d?t??a CA
?µe??µ???a a?????s??
?p???af? ap? CA. ?f??? ??a ta ped?a. ?p????fe? t?
s????? ?a? pe????e? t?? a??????µ? p??
???s?µ?p??e?ta? ??a ?p???af? t?? p?st?p???t????
Network security essentials (International
edition), William Stallings, Prentice-Hall, 2002.
ISBN 0131202715
30
????te?t?????? ??st?p???s??
?.509 ??????s? ??st?p???t???? Certificate
Revocation Lists ?d??aµ?e?

• ?e???e? ??ste?
• d?s????a epa???e?s??
• d?s????a e??es?? s???e???µ???? p?st?p???t????
  (SN)
• a???t?s? µe????? ??st?? à p??ß??µa se d??t?a
  ?aµ???? ???µ?? µet?d?s??
• ???sfat?t?ta ?at?stas?? p?st?p???t????
• ??ste? a?a????????ta? ?at? t? d?????
• ??? ?at?-apa?t?s?
• ??ste? a?a????????ta? se ??a d?µ?s?? t?p?
• bottleneck
• Dos

31
????te?t?????? ??st?p???s??
?.509 ??????s? ??st?p???t???? Certificate
Revocation Lists ???e? ???t?se??

• Distribution Point CRLs
• ??t?µet?p????? t? p??ß??µa t?? ???µ???s?? ?ta? ??
  CRLs ?????? p??? µe???e? ??a ?a t?? d?a?e????eta?
  µ?a ??t?t?ta
• ??a???????ta? ?? CRLs se µ????te?a CRL partitions
  
• ???s? ???t????? ?p?? certificate serial numbers,
  certificate issuing dates, revocation reasons
• ? s?????? ???? t?? CRLs pa???e? ??a ta entries
  t?? full CRL
• Delta-CRLs
• ?µ?µat?p???s? CRL µe ß?s? ???t???a ??????
• ??d?d??ta? µe a?af??? se µ?a CRL ß?s??
• ?e??????? ??e? t?? e??µe??se?? se s??s? µe t??
  CRL ß?s??

32
????te?t?????? ??st?p???s??
?.509 ?at?stas? ??st?p???t???? Online Certificate
Status Protocol OCSP

• ???t?????? ??a epa???e?s? p????f????? ?at?stas??
  p?st?p???t???? (Certificate Status Information,
  CSI) se p?a?µat??? ?????
• ????? ???s? CRLs
• ?e??ss?te?? p??sfat? p????f???a ?at?stas?? ap?
  CRLs
• ??a? OCSP client e?d?de? ?a? st???e? a?t?s?
  a?af???? ?at?stas?? p?st?p???t???? se ??a? OCSP
  responder
• ????? ?a ??ße? ap??t?s? a?ast???e? t?? ap?d???
  e??? p?st?p???t????
• ?? p??t?????? pe?????fe? ta µ???µata p??
  a?ta???ss??ta? µeta?? OCSP client ?a? OCSP
  responder ??a t?? a?t?s? ?a? ap??t?s? a?af????
  ?at?stas??
• RFC2560, 1999

33
????te?t?????? ??st?p???s??
?.509 ?at?stas? ??st?p???t???? OCSP. ??t?t?te?
OCSP Responder
OCSP_Res EKRORStatus(CA)
OCSP_Req.Status(CA)
A
OCSP Client
CA
Relying Party
Certificate Subject
34
????te?t?????? ??st?p???s??
?.509 ?at?stas? ??st?p???t???? OCSP Request
OCSP request   -- protocol version --
TargetCertID // might be a list
hashAlgorithm // Identifier,
issuerNameHash // Hash of Issuer's DN
issuerKeyHash // Hash of Issuers public key
serialNumber // CertificateSerialNumb
er -- signature // signs the Request,
optional
35
????te?t?????? ??st?p???s??
?.509 ?at?stas? ??st?p???t???? OCSP Response
OCSP response   -- protocol version -- name
of the responder -- response -- target
certificate identifier -- certificate status
// good, revoked, unknown -- response validity
interval -- RevokedInfo -- revocationTime
-- revocationReason -- thisUpdate //
time at which status being indicated is known to
be correct -- nextUpdate // time at which
newer info will be available about the status
-- producedAt // time at which the OCSP
responder signed this response -- signature
algorithm Identifier -- signature computed
across hash of the response
36
????te?t?????? ??st?p???s??
?.509 ?at?stas? ??st?p???t???? ???a ???t?????a

• ?a s??µata µe CRLs pa?????? negative CSI
  p????f???a, d??ad? ??a ?sa certificates ?????
  a?a????e?
• OCSP complete CSI, ?p?? ?a? ta a??????a
• Simple Certificate Validation Protocol (SCVP)
• ??a? client e?t?? ap? certificate revocation
  status µp??e? ?a a?t??e? certificate validation,
  ? a??s?de? p?st?p???s??
• Certificate Revocation Status (CRS)
• H CA d?µ?s??p??e? se ?at?????, p.?., ?a??µe????,
  ??a ??f???? ?p??e??aµµ??? µ???µa ??a ???e
  certificate p?? ??d?se ? a?a???ese.
• Certificate Revocation Trees (CRT)
• ???a? ??a hash binary tree µe f???a ?a pe???????
  d???se?? ?at?stas?? p?st?p???t????
• G?????? epa???e?s?, ?????? f??t?? st?? a?a???s?
  t?? tree

37
?p??es?e? ??st?p???s??
?p?d?µ? PKI

• ?as???? ??t?t?te? ??a?efa?a??s?
• ?p??e?µe??
• ??t?t?ta ??a t?? ?p??a e?d?deta? t? p?st?p???t???
  ? ??a ta ?a?a?t???st??? t??. ??af??eta? ?a? ??
  s??d??µ?t??.
• ?a???e? a?t?s? a?????s??
• ??d?t??a a???
• ???? p?st?p???s?? (CA)
• ??d?de? ?a? ?p????fe? ??f?a?? t? p?st?p???t???
• ?as???µe?? ????? (relying party)
• ?as??eta? st? p?st?p???t??? ?a? st?? e?????t?t?
  t?? ??a ?a epa???e?s? t?? ta?t?t?ta t??
  ?p??e?µ???? µe t? ?p??? ???e? ?a (s??)d?a??a?e?
• Authorized Party (p.?., OCSP responder)
• ?a???e? a?t?s? a?????s?? e??? p?st?p???t???? p??
  ??e? e?d?se?

38
?p??es?e? ??st?p???s??
?p?d?µ? PKI. ?p??es?e? ??st?p???s?? ?at? ETSI
?p??es?a ????af?? (Registration
service) ?p?ßeßa???e? t?? ta?t?t?ta ?a? ta
?a?a?t???st??? t?? ?p??e?µ????. ?e???aµß??e?
ap?de??? ?at???? private key ap? t? ?p??e?µe??
p?? a?t?st???e? st? public key. ?a???eta? ap? t??
???? ????af?? (RA, Registration Authority).
?p??es?a ?a?a????? ??st?p???t???? (Certificate
generation service) ?a???e? ?a? ?p????fe? t?
certificate ßas???µ??? st?? ta?t?t?ta ?a? sta
?a?a?t???st??? p?? ep?ßeßa???e? ? a??? e???af??
(RA) ?p??es?a ?????s?? (Dissemination
service) ??a??e? ta p?st?p???t??? sta ?p??e?µe?a
?a? sta relying parties. ?p?s?? d?a??e? t???
????? p?? ??te? ? CA ?a? ???e p???t??? ? p?a?t???
??a t? ???s? ?a? d?a?e???s? t?? p?st?p???t????.
ETSI TS 101 456 v 1.2.1, Policy requirements for
certification authorities issuing qualified
certificates, April 2002
39
?p??es?e? ??st?p???s??
?p?d?µ? PKI. ?p??es?e? ??st?p???s?? ?at? ETSI
?p??es?a ??a?e???s?? ??????s?? (Revocation
management service) ?pe?e????eta? a?t?se?? ?a?
a?af???? ??a a?????s? ?a? a?a?aµß??e? t??
?at?????? e????e?a. ?p??es?a ?at?stas??
??????s?? (Revocation status service) ??a??e?
revocation status information sta relying
parties. ?p??e? ?a e??a? real-time service ? ?a
e?te?e?ta? se ta?t? ??????? d?ast?µata. ?p??es?a
????es?? ?sfa???? ???ta??? ???st? (Subscriber
device provision service) ???et??µ??e? ?a?
pa???e? µ?a signature-creation device se
?p??e?µe?a (optionally)
ETSI TS 101 456 v 1.2.1, Policy requirements for
certification authorities issuing qualified
certificates, April 2002
40
?p??es?e? ??st?p???s??
?p?d?µ? PKI. Certificate Service Provider

• Certificate Service Provider (CSP)
• ? ??????? ?p??es??? p?st?p???s?? (???)
• f?s??? ? ??µ??? p??s?p? p?? e?d?de? p?st?p???t???
  ? pa???e? ???e? ?p??es?e? s??afe?? µe t??
  ??e?t??????? ?p???af??
• ??a µp??e? ?a e??a?
• Certification Authority
• Registration Authority
• Authorized Party
• Disseminator
• Revocation Manager
• Status Responder
• ..

41
?p??es?e? ??st?p???s??
?p?d?µ? PKI. Certificate Policy

• ????t??? ??st?p???s?? (Certificate Policy, CP)
• d????e? t? ep?ped? e????s?? p?? d?a??te? ???e
  p?st?p???t??? p?? e?d?de? ??a? ???
• ? ???? e????s?
• ?p???e? t? ?at? p?s? µ?a ??t?t?ta µp??e? ?a
  e??a? ß?ßa?? ??a t? ta?t?t?ta p?? e??a?
  s?s?et?sµ??? µe t? d?µ?s?? ??e?d? ?a? t? p??s?p?
  t?? ?p???? t? ???µa pa?at??eta? st? p?st?p???t???
• ape??????e? µe p?s? asf??e?a t? s?st?µa, t?
  ?p??? ???s?µ?p??????e ??a t?? pa?a???? t??
  p?st?p???t???? ?a? (d???t???) ??a t?? pa??d?s?
  t?? ?d??t???? ??e?d??? st? s??d??µ?t?, e?te?e? t?
  ?a????? t??
• a?t?p??s?pe?e? t? ßeßa??t?ta ?t? t?
  p?st?p???t??? µp??e? ?a ???s?µ?p????e? ??a t??es?
  t?? s???e???µ???? s??a??a???

42
?p??es?e? ??st?p???s??
?p?d?µ? PKI. Certificate Policy

• G?at? d?af????? ?? ????t???? ??st?p???s?? (CPs)
• ??µ??????a t?? CA key (p?????, efa?µ???, s?s?e??
  )
• ?p????e?s?, efed?e?a ?a? a???t?s? ??e?d??? t?? CA
• ??a??µ? d?µ?s??? ??e?d??? t?? CA
• ????af? ?p??e?µ???? (???p?? ?pa???e?s?
  ?a?t?t?ta?/ ?a?a?t???st????)
• ??µ??????a ??st?p???t???? ?p??e?µ????
• ?p????e?s?, efed?e?a ?a? a???t?s? ??e?d???
  ?p??e?µ???? (p.?., ???pt???af?a?)
• ????es? p?st?p???t???? se ?p??e?µe??
• ??ad??as?e? a?????s??
• ??µ??????a, ??a??µ? ?a? ??a?e???s? ?sfa???
  ??at??e?? ???st??

43
?p??es?e? ??st?p???s??
?p?d?µ? PKI. Certificate Policy
Government of Canada
??sse?a ep?peda e????s?? St???e??de?, ?as???,
?esa??, ????? ??a p?st?p???t??? ??f?a???
?p???af?? ??a p?st?p???t??? ?µp?ste?t???t?ta?.
?? t?sse??? CPs ??f?a??? ?p???af?? af????? t?
d?a?e???s? ?a? t? ???s? p?st?p???t???? p??
pe??????? d?µ?s?a ??e?d?? p?? ???s?µ?p?????ta? se
µ??a??sµ??? a??e?t???p???s??, a?e?a??t?ta? ?a?
s?µf???a? e??a??d??s?? ??e?d???. ???s?µ?p?????ta?
??a t?? epa???e?s? e-mail clients, ??a remote
login, ??a epa???e?s? t?? ta?t?t?ta? p???t?? ?
????? ??µ???? ??t?t?t??. ?? t?sse??? CPs
?µp?ste?t???t?ta? af????? t? d?a?e???s? ?a?
???s? p?st?p???t???? p?? pe??????? d?µ?s?a
??e?d?? p?? ???s?µ?p?????ta? ??a t? d?µ??????a
??e?d??? ???pt????f?s??, s?µpe???aµß????ta? t?
µetaf??? ??e?d???. ?a p?st?p???t??? p??
????????ta? s?µf??a µe a?t?? t?? p???t???? e??a?
?at?????a ??a t?? pa???? eµp?ste?t???t?ta? se
ep????????e? (p.?., µ?s? ??ad??t???).
Treasury Board Secretariat of Canada, Public Key
Infrastructure Management in the Government of
Canada, ????? 1999
44
?p??es?e? ??st?p???s??
?p?d?µ? PKI. Certificate Policy
Government of Canada
??sse?a ep?peda e????s?? (St???e??de?, ?as???,
?esa??, ?????) ??a ta p?st?p???t??? ??f?a???
?p???af?? ?a? ??a ta p?st?p???t???
?µp?ste?t???t?ta? ste?e??? t?? ??µ?s?a?
??????s??.
Treasury Board Secretariat of Canada, Public Key
Infrastructure Management in the Government of
Canada, ????? 1999
45
?p??es?e? ??st?p???s??
?p?d?µ? PKI. Certificate Practice Statement
? ????t??? ??st?p???s?? (CP) d????e? t? ep?ped?
e????s?? p?? d?a??te? ???e p?st?p???t??? p??
e?d?de? ??a? ???. ??t??eta, ? ????s? ??a?t????
(Certificate Practice Statement, CPS) e??? ???
pe?????fe? p?? e?asfa???eta? a?t? ? e????s?
???a? ??a desµe?t??? ????af? p?? pe?????fe?
a?a??t??? t?? p?a?t??? p?? a??????e? ? ??? ??a
t?? ??d?s? ?a? d?a?e???s? p?st?p???t????
??e?t??????? ?p???af?? ? t?? pa???? ?????
?p??es??? ??st?p???s?? ?d?a ????t???
??st?p???s?? (CP) µp??e? ?a ???s?µ?p?????
pe??ss?te??? t?? e??? ???. ?µ?? ???e ???
d?a??te? d?a?e???µ??? ?a? d?af??et??? ????s?
??a?t???? (CPS).
46
?p??es?e? ??st?p???s??
?p?d?µ? PKI. Certificate Practice Statement

• H ????s? ??a?t???? (CPS) e??? ??? pe?????fe? p??
  e?asfa???eta? ? CP
• ?at? ????
• d?ad??as?e? f?s???? asfa?e?a?
• e?e?d??e?µ??? p??s?p??? p?? apas???e?
• d?ad??as?e? p?? ???s?µ?p??e? ??a t?? asf??e?a t??
  p??s?p????
• ?p???e?se?? p?? a?a?aµß??e? ??a?t? t??
  s??d??µ?t?? t?? ?p??es??? t??
• ?????te????? ?p?d?µ? p?? d?a??te? ?a? ta p?????ta
  p?? ???s?µ?p??e?
• d?ad??as?e? p?? ????ete? ??a t?? p??stas?a
  ap????t??
• asfa??st??? ?????? ?a? e????? p?? a?a?aµß??e?
  ??a?t? t??t??
• d?ad??as?e? p?? a??????e? ??a t?? a?????s? e???
  p?st?p???t????
• d?ad??as?e? p?? ???s?µ?p??e? ??a t? t???s?,
  d?a?e???s? t?? a??e??? t?? ?a??? ?a? t?? a???es?
  t?? a??e??? t?? se pe??pt?s? pa?s?? t?? e??as???
  t??

????, ap?fas? ?p a???. 248/71, ?a????sµ??
?a????? ?p??es??? ??st?p???s?? ??e?t???????
?p???af??, 15-3-2002 F?? ?/603, ?a????sµ??
?a????? ?p??es??? ??st?p???s?? ??e?t???????
?p???af??, 16 ?a??? 2002
47
?p??es?e? ??st?p???s??
??? st?? ???????? ?p????te?a. ?d???e?, ??at??µata
?a? ?a????sµ??

• ???G?? 1999/93 t?? ????pa???? ?????ß?????? (13
  ?e?. 1999) s?et??? µe t? ?????t??? p?a?s?? ??a
  ??e?t??????? ?p???af??.
• ????????? ?????G?? ?p. ????. 150 ???sa?µ???
  st?? ?????t??? ?d???a (F?? ?/125, 25/06/2001)
• ?????? ?p?t??p? ???ep?????????? ?a? ?a??d??µe???
  (????), ap?fas? ?p a???. 248/71, ?a????sµ??
  ?a????? ?p??es??? ??st?p???s?? ??e?t???????
  ?p???af??, 15-3-2002 (F?? ?/603/16-05-02)
• ?????? ?p?t??p? ???ep?????????? ?a? ?a??d??µe???
  (????), ap?fas? ?p a???. 295/65, ?a????sµ?? ??a
  t?? ??e???t??? ??ap?ste?s? t?? ?a????? ?p??es???
  ??st?p???s?? (F?? 1730/?/24-11-03)

48
?p??es?e? ??st?p???s??
??? st?? ???????? ?p????te?a. ?d???e?, ??at??µata
?a? ?a????sµ??
?d???e? ?a? s?st?se?? - ???sµ??
?p????f?? F?s??? ? ??µ??? p??s?p? p?? ?at??e?
d??ta?? d?µ??????a? ?p???af?? ?a? e?e??e? e?te
??a ???a??asµ? t?? e?te e? ???µat?? f?s???? ?
??µ???? p??s?p?? ??e?t?????? ?p???af? ?ed?µ??a
se ??e?t?????? µ??f? ta ?p??a e??a? s???µµ??a se,
? ?????? s?s?et???µe?a µe, ???a ??e?t??????
ded?µ??a ?a? ta ?p??a ???s?µe???? ?? µ???d??
ap?de???? t?? ???s??t?ta? ?ed?µ??a d?µ??????a?
?p???af?? ????s?µa?ta ded?µ??a (p.?. ??d??e? ?
?d??t??? ??e?d?? ???pt???af?a?), p??
???s?µ?p?????ta? ap? t?? ?p????f??ta ??a t?
d?µ??????a ??e?t??????? ?p???af?? ?ed?µ??a
epa???e?s?? ?p???af?? ?ed?µ??a, (p.?., ??d??e? ?
d?µ?s?a ??e?d?? ???pt???af?a?), ta ?p??a
???s?µ?p?????ta? ??a t?? epa???e?s? t??
??e?t??????? ?p???af?? ???ta?? d?µ??????a?
?p???af?? ????? ? ????sµ??? p?? ???s?µ?p??e?ta?
??a t?? efa?µ??? t?? ded?µ???? d?µ??????a? t??
?p???af?? ???ta?? epa???e?s?? ?p???af?? ????? ?
????sµ??? p?? ???s?µ?p??e?ta? ??a t?? efa?µ???
t?? ded?µ???? epa???e?s?? ?p???af??
49
?p??es?e? ??st?p???s??
??? st?? ???????? ?p????te?a. ?d???e?, ??at??µata
?a? ?a????sµ??
?d???e? ?a? s?st?se?? - ???sµ??

• ?????µ??? ??e?t?????? ?p???af? (? ??f?a??
  ?p???af?)
• ??e?t?????? ?p???af? p?? a?tap?????eta? st??
  e??? apa?t?se??
• s??d?eta? µ???s?µa?ta µe t?? ?p????f??ta
• e??a? ??a?? ?a ta?t?p???se? t?? ?p????f??ta
• d?µ?????e?ta? µe µ?sa ta ?p??a ? ?p????f?? µp??e?
  ?a d?at???se? ?p? t?? ap???e?st??? t?? ??e???
• s??d?eta? µe ta ded?µ??a sta ?p??a a?af??eta?
  ?at? t??p? ?ste ?a µp??e? ?a e?t?p?ste?
  ?p??ad?p?te epa??????? a?????s? t?? e? ????
  ded?µ????
• ??st?p???t???
• ??e?t?????? ßeßa??s?, ? ?p??a s??d?e? ded?µ??a
  epa???e?s?? ?p???af?? µe ??a ?t?µ? p??
  ep?ßeßa???e? t?? ta?t?t?t? t??

50
?p??es?e? ??st?p???s??
??? st?? ???????? ?p????te?a. ?d???e?, ??at??µata
?a? ?a????sµ??
??at??e?? ??a a?a?????sµ??a p?st?p???t???

• ??a?????sµ??? p?st?p???t??? (? ??f?a??
  p?st?p???t???, qualified)
• p?st?p???t??? p?? a?tap?????eta? st?? a??????e?
  apa?t?se?? ?a? e?d?deta? ap? ???
• ?a a?a?????sµ??a p?st?p???t??? p??pe? ?a
  pe???aµß????? (µeta?? ?????)
• ??de??? ?t? t? p?st?p???t??? e?d?deta? ??
  a?a?????sµ???
• st???e?a a?a?????s?? t?? ??? ?a? t? ???t?? st?
  ?p??? e??a? e??atest?µ????
• ???µa t?? ?p????f??t??
• ded?µ??a epa???e?s?? ?p???af?? p?? a?t?st??????
  se ded?µ??a d?µ??????a? ?p???af?? ?p? t?? ??e???
  t?? ?p????f??t??
• ??de??? t?? ??a???? ?a? t???? t?? pe???d?? ?s????
  t?? p?st?p???t????
• t?? ??d??? ta?t?p???s?? t?? p?st?p???t????
• t?? p????µ??? ??e?t?????? ?p???af? t?? ??? p?? t?
  e?d?de?
• pe?????sµ??? t?? ped??? ???s?? t?? p?st?p???t????
• ???a st? ???? t?? s??a??a??? ??a t?? ?p??e? t?
  p?st?p???t??? µp??e? ?a ???s?µ?p????e?

51
?p??es?e? ??st?p???s??
??? st?? ???????? ?p????te?a. ?d???e?, ??at??µata
?a? ?a????sµ??
??at??e?? ??a a?a?????sµ??a p?st?p???t???

• ???? ?s????te? ??a ??? p?? e?d?d??? a?a?????sµ??a
  p?st?p???t???
• ap?de??????? a???p?st?a
• pa?????? ?p??es?e? ?ata????? ?a? a?????s??
• d?asfa?????? ?t? ? ?µe??µ???a ??d?s?? ? a?????s??
  p?st?p???t???? µp??e? ?a p??sd????ste? epa???ß??
• p??ßa????? se epa???e?s? t?? ta?t?t?ta? ?a? t??
  ?a?a?t???st???? t?? at?µ?? st? ???µa t?? ?p????
  ??e? e?d??e? a?a?????sµ??? p?st?p???t???
• apas?????? p??s?p??? p?? d?a??te? eµpe???a ?a?
  p??s??ta p?? e??a? apa?a?t?ta ??a t?? pa?e??µe?e?
  ?p??es?e?.
• ???s?µ?p????? a???p?sta s?st?µata ?a? p?????ta ta
  ?p??a p??state???ta? ??a?t? t??p?p???s?? ?a?
  d?asfa?????? t?? asf??e?a t?? d?e??as???
  p?st?p???s??
• ?aµß????? µ?t?a ??a?t? t?? p?ast????f?s??
  p?st?p???t???? ?a?, se pe??pt?s? p?? ? ???
  pa???e? ded?µ??a d?µ??????a? ?p???af??, ?a
  e?????ta? t?? t???s? t?? ap????t?? ?at? t?
  d????e?a t?? pa?a????? t?? e? ???? ded?µ????
• d?a??t??? epa??e?? ???µat????? p????? ?d??? ??a
  t?? a?????? t?? e?????? ??µ???

52
?p??es?e? ??st?p???s??
??? st?? ???????? ?p????te?a. ?d???e?, ??at??µata
?a? ?a????sµ??
??at??e?? ??a a?a?????sµ??a p?st?p???t???

• ???? ?s????te? ??a ??? p?? e?d?d??? a?a?????sµ??a
  p?st?p???t???
• ?ata???f??? p????f???e? s?et??? µe ??a
  a?a?????sµ??? p?st?p???t??? ??a ?at?????? ???????
  pe???d?, ??a pa???? ap?de??t???? st???e???
  p?st?p???s?? se ??µ???? d?ad??as?e?.
• µ?? ap????e???? ded?µ??a d?µ??????a? ?p???af??
  t?? ?p??e?µ???? p??? t? ?p??? ? ??? pa??s?e
  ?p??es?e?
• p??t?? s??????? s?µßat??? s??s? µe p??s?p? p??
  ??t? ??d?s? p?st?p???t????, ?a t? e??µe??????
  s?et??? µe t??? a???ße?? ????? ???s?µ?p???s??
  t??. ?? p????f???e? ?a pa?????ta? se e????a
  ?ata??pt? ???ssa. ?p?sp?sµata t?? p????f?????
  p??pe? ?a e??a? p??s?t? ?at?p?? a?t?µat?? t??t??
  ?? ?p???? ßas????ta? st? p?st?p???t??? a?t?
• ?a ???s?µ?p????? a???p?sta s?st?µata ??a t??
  ap????e?s? p?st?p???t????, ?ste
• µ??? a?µ?d??? ?a µp????? ?a d?e?e????? e?sa?????
  ?a? t??p?p???se??
• ?a e??a? d??at? ? ????????st? a???t?s?
  p?st?p???t???? µ???? st?? pe??pt?se?? e?e??e? ??a
  t?? ?p??e? ??e? d??e? ? s???at??es? t?? ?at????

53
??f?a??? ?p???af??
Ge???? ?a?a?t???st???

• ?as??? a???p???s? ???pt???af?a? d?µ?s??? ??e?d???
• ??????? µe t?? ?d???e??? ?p???af?
• ?a???e? t?? e??? d??at?t?te?
• ?pa???e?e? t?? ?p????f??ta
• ???e?t???p??e? ta pe??e??µe?a t?? µ???µat?? ?at?
  t?? ?µe??µ???a t?? ?p???af?? t???
• ?p??e? ?a epa???e?te? ap? t??ta µ??? ??a t??
  ep???s? f?????????
• ???at? ? ap????e?s? e??? a?t????f?? t?? ??f?a???
  ?p???af?? se ap????e?t??? µ?s?

54
??f?a??? ?p???af??
Ge???? ?a?a?t???st???

• Bit pattern p?? e?a?t?ta? ap? t? µ???µa p?? ?a
  ?p???afe?
• ???s?µ?p??e? ??p??a e?d??? p????f???a p?? e??a?
  µ??ad??? ??a t?? ap?st???a (p.?., d?µ?s?? ??e?d?)
• G?a ap?f??? p?ast???af?a? ?a? ap????s??
• ???a? ?p?????st??? e????? ?a d?µ???????e?
• ???a? e????a a?a?????s?µ? ?a? epa???e?s?µ?
• ???a? ?p?????st??? a??f??t? ?a p?ast???af??e? µe
  t??? e??? t??p???
• ?e t? ?a pa?a??e? ??a ??? µ???µa µe ???s? t??
  ?d?a? ??f?a??? ?p???af??
• ?e t? ?a pa?a??e? µ?a ???? ??f?a?? ?p???af? ??a
  ??a ded?µ??? µ???µa

55
??f?a??? ?p???af??
????p???se?? ?a? ??se??

• ?p???te? ?t? ? pa?a??pt?? d?a??te? t? d?µ?s??
  ??e?d? t?? ap?st???a
• ? s??????? asf??e?a t?? s??µat?? e?a?t?ta? ap? t?
  ?d??t??? ??e?d? t?? ap?st???a
• ? ap?st???a? µp??e? ?a ap?p????e? t?? ap?st???
  t?? µ???µat?? ?
• ?s?????eta? ?t? t? ?d??t??? t?? ??e?d? ??e?
  pa?aß?aste? ? ??ape?
• ?t? ? ???pt?? ???s?µ?p???se t? ?d??t??? ??e?d?
  ??a p?ast???af?a
• ???s?µ?p??e?ta? ?? µ?s? ??a µ? ap?p???s? ?
• ? ap?st???a? ap?ste??e, ?a? a? ?a?, p?te ?
• ? pa?a??pt?? ??aße ?
• ??? p??se???se?? t?? s??µat??
• Direct Digital Signature (?µes?)
• Arbitrated Digital Signature (µe d?a?t?s?a)

56
??f?a??? ?p???af??
Direct Digital Signature

• ?µp???e? µ??? ap?st???a ?a? pa?a??pt?
• ?p??e? ?a ???p????e? µe ???s? µe??d?? d?µ?s???
  ??e?d??? p?? ?d? s???t????a?
• ?d??aµ?a
• ? ap?st???a? µp??e? ?a ap?p????e? t?? ap?st???
  t?? µ???µat??
• ?p??e? ?a ?s????ste? ?t? t? ?d??t??? t?? ??e?d?
  ??e? pa?aß?aste? ? ??ape?
• ?t? ? ???pt?? ???s?µ?p???se t? ?d??t??? ??e?d?
  ??a p?ast???af?a
• ??a e?a?s??s?a st? rationality t?? ap?st???a
• ??a??a?a µ???d?? p??sd????sµ?? t?? ep?p?d??
  eµp?st?s???? t?? ap?st???a

57
??f?a??? ?p???af??
Arbitrated Digital Signatures

• ?µp???e? a??? ??a?t?s?a? (?rbiter)
• ?p?ß??e? t? µ???µa t?? ap?st???a ?a? t?? ?p???af?
  t?? se µ?a se??? d???µas??? ??a ?a e????e? t??
  a??e?t???t?ta t?? pe??e??µ???? t?? ?a? t??
  p????e?s?? t???
• ?et? ap? ??e??? a???p?st?a?, ? ??a?t?t??
• ???s??te? ?µe??µ???a st? µ???µa
• ???s??te? ??de??? ep?????s?? ap? ??a?t?t?
• ?p?st???e? st?? pa?a??pt?
• ????µa µe ?p???af? ap?st???a, ?µe??µ???a, ??de???
  d?a?t?s?a?
• ?pa?te? ?s???? ep?ped? eµp?st?s???? ?a? t?? d??
  µe??? ap??a?t? st?? ??a?t?t?
• ?p??e? ?a ???p????e? µe ???s? s?µµet????? ?
  ???pt???af?a? d?µ?s??? ??e?d???

58
??f?a??? ?p???af??
Arbitrated Digital Signatures. S?µµet????
???pt???af?a
?p?st???a? ? ?a? Arbiter A µ???????ta? ??a
????? µ?st??? ??e?d? ??X ?a?a??pt?? Y ?a? Arbiter
A µ???????ta? ??a ????? µ?st??? ??e?d? ??Y M
µ???µa ??a ap?st??? ap? ???
Sender X Arbiter A Receiver Y
?a???e? M, s????? ?(?) ?a? ???pt????f?µa t?? ? SAX(?)E?AXIDX H(M) St???e? ? ?a? SAX(?) st?? ?
?p????pt???afe? t?? SAX(?) µe ??X ?????e? H(M) ??a ?a ep?ßeßa??se? ? ?a? ? ?a???e? ??? ? p??? ? p?? pe????e? ?IDX ? SAX(?) Timestamp St???e? SA?(?) st?? ?
?p????pt???afe? t?? SA?(?) µe ??? ??a?t? ? ?a? SAX(?), ap????e?e?
59
??f?a??? ?p???af??
Arbitrated Digital Signatures. S?µµet????
???pt???af?a

• ?e??pt?se?? d?af???a? (dispute) ?p???s? µ?s?
  Arbiter A
• O ? ?s?????eta? ?t? ??aße ? ap? ?
• ? ? st???e? se A t? a??????? ???pt???af?µ???
  µ???µa
• E?A? IDX M E?A?IDX ?(M)
• ? A ???s?µ?p??e? ??Y, ap????pt???afe? ?a? e???e?
  IDX,M ?a? SAX(?)
• ? A ???s?µ?p??e? ???, ap????pt???afe? t?? SAX(?)
  ?a? e???e? IDX,?(M)
• ? A ep?ßeßa???e? ?t? ? ? ??aße ? ap? ? !!!
• ?ts?, ? ? µp??e? ?a e????e? t?? ??f?a?? ?p???af?
  t?? ? ?µµesa, µ?s? t?? ?
• ?? s??µa µp??e? ?a eµp???t?ste? ?a? µe ??e?d? KXY
  ??a eµp?ste?t???t?ta

60
??f?a??? ?p???af??
Arbitrated Digital Signatures. ???pt???af?a
??µ?s??? ??e?d???

• ??e????t?µa ? Arbiter ? de? ß??pe? t? ?
• O ? ?p????fe? t? ?? µe t? ?d??t??? t?? ??e?d? KRX
  ?a? ?at?p?? ???pt???afe? t? ap?t??esµa µe t?
  d?µ?s?? ??e?d? KU? t?? ?, pa?????ta? µ?a
  ?p??e??aµµ??? ?a? eµp?ste?t??? ??d?s? t?? ?? t??
  ??
• ?? ??, µa?? µe t? IDX ?p????feta? e? ???? µe t?
  KRX pa?????ta? t? ?? ?a? t? µ???µa a?t?
  st???eta? µa?? µe t? IDX st?? ?
• ? ? ? ?? E?R? E?UY E?R? M? IDX
  IDX
• O A e????e? a? t? d?µ?s?? ??e?d? t?? ? e??a?
  ??????, ap????pt???afe? t? ?? µe t? d?µ?s??
  ??e?d? KUX ?a? p?st?p??e? ?t? ???e ap? ?
• ? A pa???e? ??a µ???µa ?a p?? ap?te?e?ta? ap? t?
  IDX, t? timestamp ?a? t? E?UY E?R?M? , t?
  ???pt???afe? µe t? ?d??t??? t?? ??e?d? KRA ?a? t?
  st???e? st?? ?
• ? ? ? Ma E?R? E?UY E?R?M? IDX ?
  
• ? ? a?a?t? t? d?µ?s?? ??e?d? t?? ?, E?U?,
  ap????pt???afe? t? ?a a?a?t? t? E?UY E?R?M?
  , t? ap????pt???afe? µe t? ?d??t??? t?? ??e?d?
  t?? KR?, a?a?t? t? E?R?M?, a?t?e? t? d?µ?s??
  ??e?d? KUX t?? ? ?a? a? e??a? ?????? a?a?t? t? ?X