x.509 standard and ca’s operation certificate path validation dec. 18, 2001 2001824 c&is lab....
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X.509 standard and CA’s operationX.509 standard and CA’s operation
Certificate path validationCertificate path validation
Dec. 18, 20012001824C&IS lab.
Vo Duc Liem
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ContentsContents
1. Introduction
2. Previous Works
3. Proposed method
4. Assessment
5. Conclusion and further work
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IntroductionIntroduction
Certificate path validation A & B has certificate from different CA
A trust CA-B?
CA-A & CA-B cross certificate
easy!
Not Cross validation path from
CA-B to “most trusted” CA by A
A spend time & power for verifying
Root CA
CA-B
B
CA-A
A
Cross ?
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Previous workPrevious work
Method of certificate path validation
Full path validation Computation O(n)
Delegation certificate path validation O(1)
Simple Certificate Validation Protocol O(1)
Offline Path Validation* O(1) or no cost
*: Method is presented in IWAP01
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Proposed methodProposed method
Assumption
Number of CA’s not huge as user
CA is stable entity and play right role,
CA is responsible in law
The trust between CA’s: CA trust his child
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Validating ProcessValidating Process
CA-B
CA
Root CA
User B
CA-A
CA
User A
List of valid CAs(May sign by root CA)
ECA
ECA1
Cert. of CA-B
Cert. of B
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List of Valid CAList of Valid CA
ECA1: produce list of its child CA’s, sign and send to ECA2
ECA2 verifies ECA1 signature; sign on list
…
Root CA: check signature and sign
List of ECA
Issuer ECA1
…
Root CA
Root CA signature Alg.
Root CA signature on all above fields
Exp. List of valid CA
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Steps of validationSteps of validation
A check in CRL for B certificate
If not, verify by public key of CA-B (ECA)
Check existence of CA-B in the list of valid CA of ECA1
If exist, verify CA-B’s certificate by ECA1 public key
Verify the list of valid CA of ECA1 by public key of Root CA
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AssessmentAssessment
Correctness Only right public key can verify signature made by respective
private key
Security No one can make fake certificate or change the list without
knowing of private key
The list of valid CA does not need change frequently
Need 3 signature verification process
Reduce power computing for users.
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Conclusion and further workConclusion and further work
Understand X.509 and CA’s operation
Proposed method of Certificate path validation
For future: Find out all possible attack
Consider cross-certificate at high level
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ReferencesReferences
① Cryptography and Network Security: Principles and Practice, William Stalling, Prentice Hall 1998
② ITU-T X.509 v3 recommendation (1997)③ IETF – RFC 2459, Internet X.509 Public Key Infrastructure
Certificate and CRL Profile, 1999④ IETF – RFC 2560, Internet X.509 Public Key Infrastructure
Online Certificate Status Protocol – OCSP, 1999⑤ IETF – Internet drafts, Simple Certificate Validation Protocol,
2001⑥ NIST - Public key infrastructure study – Final report 1997⑦ Network Security: PRIVATE Communication in a PUBLIC
World, C. Kaufman, R. Perlman, M, Speciner, Prentice Hall 1995.
⑧ Efficient offline path validation – Byoungcheon Lee, Kwangjo Kim, Moongseog Seo, Weonkeun Huh - IWAP 2001 document
⑨ On the complexity of Public-key Certificate Validation – Diana Berbecaru, Antonio Lioy, Marius Marian – ISC2001, LNCS 2200, p183-203, 2001