ISA 562 Information Systems Theory and Practice

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ISA 562Information Systems Theory and Practice

• 10. 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 RSAMD5, 512 CUS, SVA,
OGMU, OUISE 9/9/99-1/1/1 CUS, SVA, OGMU,
OUISE, CNAlice 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 others 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 GRAPH
Internet Policy Registration Authority
IPRA
Policy Certification Authorities (PCAs)
PERSONA
RESIDENTIAL
MID-LEVEL ASSURANCE
HIGH ASSURANCE
Anonymous
MITRE
GMU
Virginia
Certification Authorities (CAs)
Abrams
LEO
Fairfax
CS
Subjects
Grover
Grover
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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
Brand
Brand
Geo-Political
Bank
Acquirer
Customer
Merchant
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Certificate Revocation

• Sometimes, the issuer need to recant certificate
• The subjects 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
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HIERARCHICAL STRUCTURE WITH ADDED LINKS
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TOP-DOWN HIERARCHICAL STRUCTURE
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FORREST OF HIERARCHIES
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MULTIPLE ROOT CAs INTERMEDIATE CAs MODEL
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THE CERTIFICATE TRIANGLE
user
X.509 identity certificate
X.509 attribute certificate
attribute
public-key
SPKI certificate
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2-WAY SSL HANDSHAKE WITH RSA
Handshake Protocol
Record Protocol
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SINGLE ROOT CA MODEL
Root CA
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Root CA
User
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SINGLE ROOT CAMULTIPLE RAs MODEL
Root CA
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Root CA
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MULTIPLE ROOT CAs MODEL
Root CA
Root CA
Root CA
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Root CA
User
Root CA
User
Root CA
User
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ROOT CA INTERMEDIATE CAs MODEL
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MULTIPLE ROOT CAs PLUS INTERMEDIATE CAs MODEL
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MULTIPLE ROOT CAs PLUS INTERMEDIATE CAs MODEL
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MULTIPLE ROOT CAs PLUS INTERMEDIATE CAs MODEL
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MULTIPLE ROOT CAs INTERMEDIATE CAs 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
Bob Web browser
www.host.com Web server
Server-side SSL
Ultratrust Security Services
www.host.com
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SERVER-SIDE MASQUERADING
Bob Web browser
www.host.com Web server
Ultratrust Security Services
Server-side SSL
Server-side SSL
Mallorys Web server
www.host.com
BIMM Corporation
www.host.com
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SERVER-SIDE MASQUERADING
Bob Web browser
www.host.com Web server
Ultratrust Security Services
Server-side SSL
Server-side SSL
BIMM Corporation
Mallorys Web server
www.host.com
Ultratrust Security Services
www.host.com
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MAN IN THE MIDDLEMASQUERADING PREVENTED
Client Side SSL end-to-end
Ultratrust Security Services
Bob Web browser
www.host.com Web server
Bob
Ultratrust Security Services
Client-side SSL
Client-side SSL
BIMM Corporation
BIMM Corporation
www.host.com
Mallorys Web server
Ultratrust Security Services
Ultratrust Security Services
www.host.com
Bob
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ATTRIBUTE-BASED CLIENT SIDE MASQUERADING
Joe_at_anywhere Web browser
BIMM.com Web server
Client-side SSL
Ultratrust Security Services
Ultratrust Security Services
Joe_at_anywhere
BIMM.com
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ATTRIBUTE-BASED CLIENT SIDE MASQUERADING
Alice_at_SRPC Web browser
BIMM.com Web server
Client-side SSL
SRPC
Ultratrust Security Services
Alice_at_SRPC
BIMM.com
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ATTRIBUTE-BASED CLIENT SIDE MASQUERADING
Bob_at_PPC Web browser
BIMM.com Web server
Client-side SSL
PPC
Ultratrust Security Services
Bob_at_PPC
BIMM.com
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ATTRIBUTE-BASED CLIENT SIDE MASQUERADING
Alice_at_SRPC Web browser
BIMM.com Web server
Client-side SSL
SRPC
Ultratrust Security Services
BIMM.com
PPC
Bob_at_PPC