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ISA 562 Information Systems Theory and Practice. 10. Digital Certificates. PUBLIC-KEY CERTIFICATES-1. What is a certificate?: A statement claiming some binding of attribute values Why do we need them? Identifying entities outside of domain Distributed access control What do they do? - PowerPoint PPT Presentation
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ISA 562Information Systems Theory and Practice
ISA 562Information Systems Theory and Practice
10. Digital Certificates10. Digital Certificates
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PUBLIC-KEY CERTIFICATES-1
• What is a certificate?: – A statement claiming some binding of attribute values
• Why do we need them?– Identifying entities outside of domain– Distributed access control
• What do they do?– Propagates claims:
• Certifier makes a claim that can be checked for authenticity and accepted if the recipient believe the claimant to be truthful
– Manages trust – distributed trust management
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X.509v1 CERTIFICATE
VERSION
SERIAL NUMBER
SIGNATURE ALGORIT
ISSUER
VALIDITY
SUBJECT
SUBJECT PUB KEY INFO
SIGNATURE
1
1234567891011121314
RSA+MD5, 512
C=US, S=VA, O=GMU, OU=ISE
9/9/99-1/1/1C=US, S=VA, O=GMU, OU=ISE, CN=Alice
RSA, 1024, xxxxxx
SIGNATURE
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PUBLIC-KEY CERTIFICATES
• For public-key based encryption
– sender needs public key of receiver
• For public-key digital signatures
– receiver needs public key of sender
• To establish an agreement
– both need each other’s public keys
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CERTIFICATE TRUST
• Acquisition of public key of the issuer to verify the signature– Go to through a certificate chain
• Whether or not to trust certificates signed by the issuer for this subject
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PEM CERTIFICATION GRAPHInternet Policy Registration Authority
Policy Certification Authorities (PCAs)
HIGHASSURANCE
MID-LEVELASSURANCE
RESIDENTIAL PERSONA
CertificationAuthorities
(CAs)
Abrams
Grover
SubjectsGrover
LEO
IPRA
MITRE GMU
CS
Virginia
Fairfax
Anonymous
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PUBLIC-KEY CERTIFICATES• What is a certificate?:
– A statement claiming some binding of attribute values
• Why do we need them?– Identifying entities outside of domain
– Distributed access control
• What do they do?– Propagate claims:
• Certifier makes a claim that can be checked for authenticity and accepted if the recipient believe the claimant to be truthful
– Manages trust – distributed trust management
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SECURE ELECTRONIC TRANSACTIONS (SET) CA HIERARCHY
Root
Brand BrandBrand
Geo-Political
Bank Acquirer
Customer Merchant
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Certificate Revocation
• Sometimes, the issuer need to recant certificate– The subject’s attributes have changed– The subject misused the certificate– There are forged certificates
• Published in a certificate revocation list
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CRL FORMAT
SIGNATURE ALGORITHM
ISSUER
LAST UPDATE
NEXT UPDATE
REVOKED CERTIFICATES
SIGNATURE
SERIAL NUMBER
REVOCATION DATE
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X.509 CERTIFICATES
• X.509v1– basic
• X.509v2– adds unique identifiers to prevent against reuse of
X.500 names
• X.509v3– adds many extensions– can be further extended
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X.509v3 CERTIFICATE INNOVATIONS
• distinguish various certificates– signature, encryption, key-agreement
• identification info in addition to X.500 name– internet names: email addresses, host names, URLs
• issuer can state policy and usage– good enough for casual email but not for signing checks
• limits on use of signature keys for further certification• extensible
– proprietary extensions can be defined and registered
• attribute certificates– ongoing work
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X.509v2 CRL INNOVATIONS
• CRL distribution points• indirect CRLs• delta CRLs• revocation reason• push CRLs
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HIERARCHICAL STRUCTURE
Z
X
Q
A
Y
R S T
C E G I K M O
a b c d e f g h i j k l m n o p
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HIERARCHICAL STRUCTURE WITH ADDED LINKS
Z
X
Q
A
Y
R S T
C E G I K M O
a b c d e f g h i j k l m n o p
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TOP-DOWN HIERARCHICAL STRUCTURE
Z
X
Q
A
Y
R S T
C E G I K M O
a b c d e f g h i j k l m n o p
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FORREST OF HIERARCHIES
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MULTIPLE ROOT CA’s + INTERMEDIATE CA’s MODEL
X
Q
A
R
S T
C E G I K M O
a b c d e f g h i j k l m n o p
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THE CERTIFICATE TRIANGLE
user
attribute public-key
X.509identity
certificate
X.509attribute
certificate
SPKIcertificate
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2-WAY SSL HANDSHAKE WITH RSA
Client Server ClientHello --------> ServerHello Certificate CertificateRequest <-------- ServerHelloDone Certificate ClientKeyExchange CertificateVerify [ChangeCipherSpec] Finished --------> [ChangeCipherSpec] <-------- Finished Application Data <-------> Application Data
RecordProtocol
HandshakeProtocol
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SINGLE ROOT CA MODEL
RootCA
a b c d e f g h i j k l m n o p
RootCA
User
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SINGLE ROOT CAMULTIPLE RA’s MODEL
RootCA
a b c d e f g h i j k l m n o p
RootCA
User RA
User RA
User RA
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MULTIPLE ROOT CA’s MODEL
RootCA
a b c d e f g h i j k l m n o p
RootCAUser
RootCA
RootCA
RootCAUser
RootCAUser
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ROOT CA + INTERMEDIATE CA’s MODEL
Z
X
Q
A
Y
R S T
C E G I K M O
a b c d e f g h i j k l m n o p
25
MULTIPLE ROOT CA’s PLUS INTERMEDIATE CA’s MODEL
X
Q
A
R
S T
C E G I K M O
a b c d e f g h i j k l m n o p
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MULTIPLE ROOT CA’s PLUS INTERMEDIATE CA’s MODEL
X
Q
A
R
S T
C E G I K M O
a b c d e f g h i j k l m n o p
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MULTIPLE ROOT CA’s PLUS INTERMEDIATE CA’s MODEL
X
Q
A
R
S T
C E G I K M O
a b c d e f g h i j k l m n o p
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MULTIPLE ROOT CA’s + INTERMEDIATE CA’s MODEL
• Essentially the model on the web today
• Deployed in server-side SSL mode
• Client-side SSL mode yet to happen
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SERVER-SIDE MASQUERADING
BobWeb browser
www.host.comWeb serverServer-side SSL
UltratrustSecurityServices
www.host.com
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SERVER-SIDE MASQUERADING
BobWeb browser
www.host.comWeb server
Server-side SSL UltratrustSecurityServices
www.host.comMallory’sWeb server
BIMMCorporation
www.host.com
Server-side SSL
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SERVER-SIDE MASQUERADING
BobWeb browser
www.host.comWeb server
Server-side SSL UltratrustSecurityServices
www.host.comMallory’sWeb server
Server-side SSL
BIMMCorporation
UltratrustSecurityServices
www.host.com
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MAN IN THE MIDDLEMASQUERADING PREVENTED
BobWeb browser
www.host.comWeb server
Client-side SSL
UltratrustSecurityServices
www.host.com
Mallory’sWeb server
BIMMCorporation
Client-side SSL
UltratrustSecurityServices
www.host.com
Client Side SSLend-to-endUltratrust
SecurityServices
Bob
BIMMCorporation
UltratrustSecurityServices
Bob
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ATTRIBUTE-BASED CLIENT SIDE MASQUERADING
Joe@anywhereWeb browser
BIMM.comWeb serverClient-side SSL
UltratrustSecurityServices
BIMM.com
UltratrustSecurityServices
Joe@anywhere
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ATTRIBUTE-BASED CLIENT SIDE MASQUERADING
Alice@SRPCWeb browser
BIMM.comWeb serverClient-side SSL
UltratrustSecurityServices
BIMM.com
SRPC
Alice@SRPC
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ATTRIBUTE-BASED CLIENT SIDE MASQUERADING
Bob@PPCWeb browser
BIMM.comWeb serverClient-side SSL
UltratrustSecurityServices
BIMM.com
PPC
Bob@PPC
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ATTRIBUTE-BASED CLIENT SIDE MASQUERADING
Alice@SRPCWeb browser
BIMM.comWeb serverClient-side SSL
UltratrustSecurityServices
BIMM.com
SRPC
PPC
Bob@PPC