PKI interoperability issues
for UK Government
Richard Lampard
Richard.Lampard@cesg.gsi.gov.uk
Structure
1.
2.
3.
4.
5.
What is CLOUD COVER?
Interoperability testing
Trust models
Wish list
Summary
1.
What is CLOUD COVER?
CLOUD COVER aims to ensure that
government departments have access to the
widest possible range of secure, interoperable
and cost effective PKI solutions.
2.
Interoperability testing
CA
CA
CA
2.
Interoperability testing
PCA
CA
PCA
CA
PCA
2.
Interoperability testing
• COAST system is very, very simple …
• … but it took a lot of work to achieve
interoperability!
2.
Interoperability testing
• Experiences in COAST
– misinterpretations of standards e.g. wrong version
– encoding problems e.g. DER versus BER,
GeneralizedTime vs UTCTime, DN ordering
– problems with tools e.g. ASN.1 compiler bugs
– dealing with incorrect behaviour e.g. processing
certification requests
– missing functionality e.g. ARLs
– mistakes e.g. keyUsage & basicConstraints
– invalid assumptions e.g. populating keyIdentifier
– implementation limitations e.g. serial number length
2.
Interoperability
testing
Very hard!
Simple,
interoperable
solution
Fully functional,
interoperable
solution
Very, very
hard indeed!
Requirement
Fully functional,
non-interoperable
solution
2.
Interoperability testing
CA
CA
CA
Repository
CA
CA
CA
CA
CA
CA
CA
CA
2.
Interoperability testing
HMG Root
CA
(Baltimore)
Ministry of
Education
Ministry of
Transport
Ministry of
Works
Ministry of
Plenty
Ministry of
Truth
(Entrust)
(Entegrity)
(Baltimore)
(Spyrus)
(NIST)
2.
Interoperability testing
• Conclusion?
• It doesn’t work!
2.
Interoperability testing
• Experiences with testbed:
– on-line cross certification relies upon proprietary
protocol exchanges, procedures and token standards
– certificate extensions not processed
– directory schema e.g. same OID representing
different object classes
– inability to use same Directory
– name encoding e.g PrintableString vs TeletextString,
RFC 822 address included in DN
2.
Interoperability testing
• Manual cross certification between different
products is limited
–
–
–
–
achieved between other products and Notary
using Entegrity PKIBench toolkit
pre-certificate imported to Notary CA
Entegrity token created for it
– could develop similar toolkits for all other products
2.
Interoperability testing
• What is happening to the IETF!?
– divergent working groups (PKIX, SPKI, OpenPGP)
– competing PKIX standards (CMC versus CMP)
– massive proliferation of standards ...
2.
Interoperability testing
Representation of elliptic curve DSA (ECDSA) keys and signatures in Internet X.509 PKI certificates
Certificate management message formats (CMMF)
Certificate management messages over CMS (CMC)
Caching on-line certificate status protocol
Web based certificate access protocol (WebCAP/1.0)
Enhanced CRL distribution options(OCDP)
Time stamp protocols
Data validation and certification server protocols
PKIX roadmap
Qualified certificates
Diffie-Hellman proof of possession algorithms
An Internet attribute certificate profile for authorisation
Basic event representation token v1
Extending trust in non-repudiation tokens in time
Simple certificate validation protocol (SCVP)
Using HTTP as a transport protocol for CMP
Limited attribute acquisition protocol
RFC 2459 - Certificate and CRL profile
RFC 2510 - Certificate management protocols (CMP)
RFC 2511 – Certificate request message format (CRMF)
RFC 2527 - Certificate policy and certificate practices framework
RFC 2528 – Representation of key exchange algorithm (KEA) keys in Internet X.509 PKI certificates
RFC 2559 – Operational protocols: LDAPv2
RFC 2560 – Online certificate status protocol (OCSP)
RFC 2585 – Operational protocols: FTP and HTTP
RFC 2587 – LDAPv2 schema
Operational protocols: LDAPv3
Limited attribute certificate acquisition protocol
OCSP extensions
Using HTTP as a transport protocol for CMP
Using TCP as a transport protocol for CMP
A string representation of general name – allows representation of GeneralName when not using ASN.1 encoded protocol (e.g.
configuration file)
Technical requirements for a non-repudiation service
PKIX profile for IKE – allows use of PKIX certificates with IPSec.
3.
Trust models
R
We would like to use all
three in Government ...
B
… but we are generally stuck
with hierarchies
4.
Wish list
• PKI Forum should feed into IETF PKIX WG
• Don’t forget client interoperability and Directory
issues
• Interoperability should not be exclusive among
Forum members
• Testing service or reference implementation
• Liaise with other initiatives e.g. ECAF, TIE,
Identrus
5.
Summary
• Lack of interoperability will be a major problem
for UK Government
• PKI Forum efforts are very welcome
• Ensure that the work is coordinated with other
international efforts