XML Key Management Services - Tutorial

9 December 01

Blair Dillaway

Software Architect

Microsoft Corp.

Outline

• Historical Perspective

• XKMS Overview

• Trust Models

• Using XKMS

• What’s Next

Historical Perspective

• PKI complexity has limited its use– Enrollment – multiple approaches– No std discovery approach – CAs, Certs, Keys– ‘Cert’ standardization & interpretation– Trust management

• Chain-building logic• ‘OID’ interpretation• Cross certification & cert hierarchies

– Client handling of complex ASN.1 and PKCS data structures– Effective Revocation/Validation

• Affects every client• Interoperability issues

XKMS Overview

• Define XML compatible key mgmt• Make PKI-based security easier to use

– Address multi-vendor, cross-plat issues – Support multiple Trust/PKI infrastructures– Allow clients to offload complex, and difficult,

trust assessment– Integrate key validity checks– Keep the interfaces simple– Keep interactions simple

XKMS Approach

InternetClient App

XKMS Service

Web Service App

PKI

Std. Protocols:HTTPSOAP

Std. Discovery:UDDIWSDL

Trust Models (1 of 2)

• XKMS is trust model agnostic– PKIX, PGP, Key-based, Proprietary– Services define supported model

• Similar to CA publishing a CPS• Contract between the Service and Applications

• XKMS doesn’t tell one how to do this or what the business relationship should be

Trust (2 of 2)

• But, there’s still a bootstrapping problem– Apps need to pick the right trust infrastructure– Need trust in an XKMS service(s)

• XKMS doesn’t define how to handle this• Will likely mirror what already happens

– Keys for high-volume, low-value, Services widely distributed

– Keys for Enterprise Services distributed via internal trust

– Keys for vertical market, high-value, apps using high assurance mechanism

Using XKMS (1 of 2)

• Getting started– Pick the right service, get its usage profile

info, etc.– Tailor the XKMS client for the service

• Cache the service identifying info• Set the service URL• Understand supported KeyInfo elements• Structural requirements on data (i.e., KeyID or

KeyName formatting)

Using XKMS (2 of 2)

• Operations– Register your public key– Locate other public keys (optional)

• Ex: find key so you can send encrypted data to others

– Check validity/trustworthiness of public keys• Authentication, Signed documents, …• Possibly before sending encrypted data

– Manage your keys• Revoke• Update associated attributes• Recover/roam your private key

Next Steps

• Refinement of XKMS 1.1– Interface refinement– Xml Signature context issues– Bulk operations– Message level authentication, integrity,

confidentiality– Update for conformance with latest XML stds

• Move forward as a W3C recommendation

XKMS Message Samples

Registration Request<soap:Envelope > <soap:Body> <Register xmlns="http://www.xkms.org/schema/xkms-2001-01-

20"> <Prototype Id="KB01"> <Status>Valid</Status> <KeyID>abc123</KeyID> <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#"> <KeyName>mykey</KeyName> <KeyValue> <RSAKeyValue>

<Modulus>8nSoscDtBoSA5jiqrMn3yg0TRvRdfFFzrutP7zHATX4lD8cgPns=</Modulus>

<Exponent>AQAB</Exponent> </RSAKeyValue> </KeyValue> <RetrievalMethod URI="http://someURI"

Type="http://someType" />

<PassPhrase>85XRXbVMov0efQi1NvS41Q1YsZg=</PassPhrase>

<ValidityInterval>

<NotBefore>2000-09-20T12:00:00.0000000-07:00</NotBefore>

<NotAfter>2001-09-20T12:00:00.0000000-07:00</NotAfter> </ValidityInterval> <KeyUsageType>Signature</KeyUsageType> <KeyUsageType>Exchange</KeyUsageType> </Prototype> <AuthInfo> <AuthUserInfo> <ProofOfPossession> <Signature xmlns="http://www.w3.org/2000/09/xmldsig#"> <SignedInfo> <CanonicalizationMethod

Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315" />

<SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" />

<Reference URI="#KB01"> <DigestMethod

Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />

<DigestValue>mX8qoz9e+Ko01d4GcfLiyBeFg5Q=</DigestValue>

</Reference> </SignedInfo> <SignatureValue>KKRHMd5eL7wwBG1Xs7A=</SignatureValue> </Signature> </ProofOfPossession> <KeyBindingAuth> <Signature xmlns="http://www.w3.org/2000/09/xmldsig#"> <SignedInfo> <CanonicalizationMethod

Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315" />

<SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#hmac-sha1" />

<Reference URI="#KB01"> <DigestMethod

Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />

<DigestValue>mX8qoz9e+1d4GcfLiyBeFg5Q=</DigestValue> </Reference> </SignedInfo> <SignatureValue>9uT2hVmuZ4sBLk414=</SignatureValue> </Signature> </KeyBindingAuth> <PassPhraseAuth>JMffIc07Z23iJelIXHE=</PassPhraseAuth> </AuthUserInfo> </AuthInfo> <Respond> <string>KeyName</string> <string>X509Cert</string> </Respond> </Register> </soap:Body></soap:Envelope>

Register Result<soap:Envelope > <soap:Body> <RegisterResult xmlns="http://www.xkms.org/schema/xkms-2001-01-20"> <Result>Success</Result> <Answer> <KeyBinding Id="KB01"> <Status>Valid</Status> <KeyID>abc123</KeyID> <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#"> <KeyName>mykey</KeyName> <X509Data> <X509SubjectName>CN=MyName, O=Microsoft</X509SubjectName> <X509IssuerSerial> <X509IssuerName>CN=TheCA</X509IssuerName> <X509SerialNumber>123456</X509SerialNumber> </X509IssuerSerial> <X509Certificate>Thn3s9ozskDXj1ibjrhxz092LG4ivz+3ARpNT+mARKY=</X509Certificate> </X509Data> <ValidityInterval> <NotBefore>2000-09-20T12:00:00.0000000-07:00</NotBefore> <NotAfter>2001-09-20T12:00:00.0000000-07:00</NotAfter> </ValidityInterval> <KeyUsageType>Signature</KeyUsageType> <KeyUsageType>Exchange</KeyUsageType> </KeyBinding> </Answer> </RegisterResult> </soap:Body></soap:Envelope>

Locate Request<soap:Envelope> <soap:Body> <Locate xmlns="http://www.xkms.org/schema/xkms-2001-01-20"> <Query> <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#"> <KeyName>mykey</KeyName> </KeyInfo> </Query> <Respond> <string>KeyName</string> <string>X509Cert</string> </Respond> </Locate> </soap:Body></soap:Envelope>

Locate Response<soap:Envelope> <soap:Body> <LocateResult xmlns="http://www.xkms.org/schema/xkms-2001-01-20"> <Result>Success</Result> <Answer> <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#"> <KeyName>mykey</KeyName> <MgmtData>My Management Data</MgmtData> <SPKIData>My-SPKI-Cert</SPKIData> <KeyValue> <RSAKeyValue> <Modulus>mpk9qt0uwUb8KyMNiHEK6Y1efkBVBC3FE=</Modulus> <Exponent>AQAB</Exponent> </RSAKeyValue> </KeyValue> <X509Data> <X509SubjectName>CN=MyName, O=Microsoft</X509SubjectName> <X509IssuerSerial> <X509IssuerName>CN=TheCA</X509IssuerName> <X509SerialNumber>123456</X509SerialNumber> </X509IssuerSerial> <X509Certificate>UbCDPEkqMtlSNBxmfQt8i6tZWpqFntJilP50iRKwBLw=</X509Certificate> </X509Data> </KeyInfo> </Answer> </LocateResult> </soap:Body></soap:Envelope>

Validate Request<soap:Envelope > <soap:Body> <Validate xmlns="http://www.xkms.org/schema/xkms-2001-01-20"> <Query> <Status>Valid</Status> <KeyID>abc123</KeyID> <KeyUsageType>Signature</KeyUsageType> <KeyUsageType>Encryption</KeyUsageType> </Query> <Respond> <string>KeyName</string> <string>X509Cert</string> </Respond> </Validate> </soap:Body></soap:Envelope>

Validate Response<soap:Envelope > <soap:Body> <ValidateResult xmlns="http://www.xkms.org/schema/xkms-2001-01-20"> <Result>Success</Result> <Answer> <KeyBinding> <Status>Valid</Status> <KeyID>abc123</KeyID> <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#"> <KeyName>mykey</KeyName> <MgmtData>My Management Data</MgmtData> <X509Data> <X509SubjectName>CN=MyName, O=Microsoft</X509SubjectName> <X509IssuerSerial> <X509IssuerName>CN=TheCA</X509IssuerName> <X509SerialNumber>123456</X509SerialNumber> </X509IssuerSerial> <X509Certificate>UbCDPEkqMtlSNBxmfQt8i6tZWpqFntJilP50iRKwBLw=</X509Certificate> </X509Data> <ValidityInterval> <NotBefore>2000-09-20T12:00:00.0000000-07:00</NotBefore> <NotAfter>2001-09-20T12:00:00.0000000-07:00</NotAfter> </ValidityInterval> <KeyUsageType>Signature</KeyUsageType> <KeyUsageType>Exchange</KeyUsageType> </KeyBinding> </Answer> </ValidateResult> </soap:Body></soap:Envelope>