alternatives for message signature from sender

Alternatives for Message Signature from Sender1. Approach 1

– X12 58 to digitally sign X12 transaction set• Optional: X12 815 to transmit signer’s public key and/or location of Signer’s Public

Certificate– Include Signer’s Public Certificate as binary object in SOAP body (SOAP gateway will

use MTOM to convert binary data to MIME attachment)– Signer’s Public Certificate could be either held in an esMD specific schema (e.g.

<esMD:Certificate>) or added to CORE metadata2. Approach 2

– XML SIG in SOAP body to digitally sign payload– Include Signer’s Public Certificate as binary object in XML SIG– Digital Signature location could be either esMD specific schemas (e.g.

<esMD:Signature>) or added to CORE metadata

Alternatives for Delegation of Rights1. Signed SAML Assertion included as XML in message header (WS-Security) or message

body (esMD Metadata)– Delegator of rights signs assertion containing issuer and serial number of public

certificate of receiver of rights2. Proxy certificate included as attachment in message body

– Delegator of rights signs proxy certificate of receiver of rights3. Signed X12 815 transaction set included in functional group of X12 message

– X12 815 contains public key of receiver of rights– X12 58 is used to sign X12 815 with private key of delegator of rights

Comparison of approaches to transmitting esMD Security ArtifactsApproach Considerations

esMD Metadata • Applicable to both X12 and HPD Plus based esMD transactions• Leverages existing standards (XML SIG and SAML)• Specific to the esMD implementation guides• Could not use X12 999/824 to report errors in processing of security

artifacts. Need to select alternative error handling method.

X12 58 & X12 815 • Only applicable to X12 based transactions• X12 815 would require changes to support limited delegation of rights (e.g.

expiration date, usage)• X12 815 may require changes to carry x.509 certificate as binary object• Use for delegation of rights is new, may require new standard

Mixed Approach1. Signature: X12, Delegation:

WS-Security2. Signature: X12, Delegation:

Metadata3. Signature: Metadata,

Delegation: WS-Security

• WS-Security is specific to SOAP messages, different approach required for Direct

• Verification of holder-of-key assertion requires access to signature of delegated party

• Delegation requirements may not be clear if SOAP header is processed before payload

• X12 58 specific to X12 transactions, different approach required for HPD Plus based transactions in Use Case 1

esMD Security Metadata applied to supported transport options

Phase II CAQH CORE 270: Connectivity Rule Version 2.2.0 eHealth Exchange Direct

SAML Overview

SAML Participants• At a minimum, SAML exchanges take place between system entities referred to as a

SAML asserting party, which makes SAML assertions, and a SAML relying party, which uses assertions it has received. Most SAML assertions are in regards to a Subject about whom the assertion is being made.

• When a SAML asserting or relying party makes a direct request to another SAML entity, the party making the request is called a SAML requester, and the other party is referred to as a SAML responder.

• A relying party's willingness to rely on information from an asserting party depends on the existence of a trust relationship with the asserting party.

• SAML system entities can operate in a variety of SAML roles which define the SAML services and protocol messages they will use and the types of assertions they will generate or consume.

− Example SSO Roles: Principal – Subject of Assertion Identity Provider – SAML asserting party Service Provider – SAML relying party

SAML AssertionsAn assertion contains some basic required and optional information that applies to all its statements, and usually contains a subject of the assertion, conditions used to validate the assertion, and assertion statements.

1. Authentication statements: These are created by the party that successfully authenticated a user. At a minimum, they describe the particular means used to authenticate the user and the specific time at which the authentication took place.

2. Attribute statements: These contain specific identifying attributes about the subject (for example, that user “John Doe” has “Gold” card status).

3. Authorization decision statements: These define something that the subject is entitled to do (for example, whether “John Doe” is permitted to buy a specified item).

Confirmation MethodThe SubjectConfirmation element provides the means for a relying party to verify the correspondence of the subject of the assertion with the party with whom the relying party is communicating. The Method attribute indicates the specific method that the relying party should use to make this determination.

SAML 2.0 accounts for three different security scenarios by defining three values for the Method attribute of the SubjectConformation element, these are• holder-of-key – the attesting entity demonstrates knowledge of specific key information

to use the assertion (and thereby lay claim to some relationship with the subject within).• sender-vouches - the relying party has an existing trust relationship with the attesting

entity. The attesting entity vouches for the subject of the assertion.• bearer - any party that bears the Assertion may use the assertion.

SAML SpecificationsSAML consists of building-block components that, when put together, allow a number of use cases to be supported. The components primarily permit transfer of identity, authentication, attribute, and authorization information between autonomous organizations that have an established trust relationship.

1. Core: Defines the structure and content of both assertions and protocol messages used to transfer this information.

2. Protocols: Generalized methods to request assertions and respond to requests for assertions.

3. Bindings: Mappings of SAML protocols onto standard messaging and communication protocols.

4. Profiles: Combinations of assertions, protocols, and bindings to support a defined use case.

5. Metadata: Defines a way to express and share configuration information between SAML parties.

SAML ProtocolsRequests and responses for obtaining assertions and doing identity management.

1. Assertion Query and Request Protocol: Defines a set of queries by which SAML assertions may be obtained. The Request form of this protocol can ask an asserting party for an existing assertion by referring to its assertion ID. The Query form of this protocol defines how a relying party can ask for assertions (new or existing) on the basis of a specific subject and the desired statement type.

2. Artifact Resolution Protocol: Provides a mechanism by which SAML protocol messages may be passed by reference using a small, fixed-length value called an artifact. The artifact receiver uses the Artifact Resolution Protocol to ask the message creator to dereference the artifact and return the actual protocol message. The artifact is typically passed to a message recipient using one SAML binding (e.g. HTTP Redirect) while the resolution request and response take place over a synchronous binding, such as SOAP.

3. Authentication Request Protocol4. Single Logout Protocol5. Name Identifier Management Protocol6. Name Identifier Mapping Protocol

SAML BindingsMappings of SAML protocols onto standard messaging and communication protocols.

1. SAML SOAP Binding: Defines how SAML protocol messages are transported within SOAP 1.1 messages, with details about using SOAP over HTTP.

2. HTTP Redirect Binding: Defines how SAML protocol messages can be transported using HTTP redirect messages (302 status code responses).

3. HTTP POST Binding: Defines how SAML protocol messages can be transported within the base64-encoded content of an HTML form control.

4. SAML URI Binding: Defines a means for retrieving an existing SAML assertion by resolving a URI (uniform resource identifier).

5. HTTP Artifact Binding: Defines how an artifact (described above in the Artifact Resolution Protocol) is transported from a message sender to a message receiver using HTTP. Two mechanisms are provided: either an HTML form control or a query string in the URL.

SAML ProfilesCombinations of assertions, protocols, and bindings to support a defined use case.

1. Assertion Query/Request Profile: Defines how SAML entities can use the SAML Query and Request Protocol to obtain SAML assertions over a synchronous binding, such as SOAP.

2. Artifact Resolution Profile: Defines how SAML entities can use the Artifact Resolution Protocol over a synchronous binding, such as SOAP, to obtain the protocol message referred to by an artifact.

3. SSO Profiles of SAML4. Name Identifier Mapping Profile5. SAML Attribute Profiles

Example 1: esMD Use Case 1A Provider delegates eMDR registration to an HIH. A SAML Assertion is used to communicate this delegation to the payer.• Participants

‒ SAML Asserting Party: Provider (or trusted third party SAML Service)‒ SAML Relying Party: Payer‒ Subject of SAML Assertion: HIH

• The HIH signs the registration request using their private key.• Either the HIH or Payer requests an assertion from the Provider/SAML Service. • The Provider/SAML Service signs the HIH’s public key and places this in the

SubjectMethod of the Assertion which is then sent to the requestor.• The Payer uses the public key provided in the SubjectMethod to verify the signature of the

HIH on the registration request.• If the signature is valid, the requirements of the Holder-of-Key confirmation method are

satisfied. The Payer knows that the HIH is the Subject of the Assertion and any assertions the Provider/SAML Service has made apply to that HIH.

Use of SAML for esMD Delegation of RightsBenefits• Provides structured format to exchange assertions• Holder-of-Key Confirmation Method aligns well to esMD requirements• OASIS specifications can be combined to support variety of use cases

Considerations• Providers/SAML Service, HIHs, and Payers must support components of SAML including

SAML Core and any implementation specific profiles• Either the Provider or a trusted third party SAML Service working on their behalf would

require a SAML endpoint capable of creating and signing assertions using their private key• SAML Assertions are usually generated and consumed for a specific request and not

stored or exchanged as documents for long periods of time

Security Standards under Review for esMD

Transaction TimelineAn esMD transaction begins with the creation of some type of electronic content (e.g. X12 274, 277, or 275 message or an HPD Plus DSML, CDA, or PDF document). As the content is packaged into a message and sent, security elements are added at points along the timeline dependent on the standard(s) selected and the purpose of the security element. This process is reversed on the receiving end.

Electronic Content Created

Content Stored as a document

XD* Metadata

Content packaged

into payload

Message created

Message Sent

DSG Signature

X12 58 Signature

WS-Security Encryption

(transport level)

CAQH CORE Metadata

Internal Systems Gateway

Message Received

Process Header

Process Payload

X12 58 Signature

WS-Security

CAQH CORE/ XD* Metadata

Process Content

DSG Signature

Internal SystemsGatewayInternet

Store Content

IHE DSGThe Document Digital Signature (DSG) content profile specifies the use of XML Advanced Electronic Signatures (XAdES) for documents that are shared between organizations.

Process Flow for Phase 1 Sending Medical Documentation

Transaction Structure

Extensions to MetadataThis approach would extend existing metadata to support the exchange of the required security information. For esMD, this would require extensions to CAQH CORE and XD* metadata. We would need to work with the relevant organizations to seek inclusion of these changes in future specifications.

Process Flow for UC1 Registration


X12 58This standard defines the data formats for authentication, encryption, and assurances in order to provide integrity, confidentiality, and verification and non-repudiation of origin for two levels of exchange of EDI formatted data defined by ASC X12.



WS-SecurityThis specification extends SOAP Messages to provide three main security capabilities: the ability to send security tokens as part of a message, message integrity, and message confidentiality.



esMD Security Requirements

Identity RequirementsRequirement Description Registration Send

eMDRSend eMD

Include Sender's public digital certificate in transaction

- Receiver traces certificate to root CA in order to verify sender's identity.- Receiver uses public key and digital signature to verify authenticity.

y y y

Include additional public digital certificates in transaction

- Transaction includes public digital certificates of all other parties that have digitally signed something in the transaction.- Receiver traces certificates to root CAs in order to verify identity of all parties that have digitally signed something in the transaction.- Receiver uses public keys and digital signatures to verify authenticity of all parties that have digitally signed something in the transaction.- Receiver uses certificates to verify all delegation of rights artifacts created by all parties that have digitally signed an assertion

y n y

Authenticity Requirements 1/2Requirement Description Registration Send

eMDRSend eMD

Digital Signature of portion of transaction (message)

- All parties that interact with transaction can sign it - Receiver uses digital signature to verify authenticity of message across all hops

n n n

Digital Signature of entire transaction (message)

- Sender of message can sign it - Receiver uses digital signature to verify authenticity of message

y y y

Digital Signature of a contributor to a document (payload)

- Multiple content creators sign relevant portions of payload- Receiver uses digital signatures to verify authenticity of content

n n Level 1 - nLevel 3 - y

Digital Signature of an entire document (payload)

- Single content creator signs entire payload- Receiver uses digital signatures to verify authenticity of content

n n Level 1 - nLevel 2 - y

Digital Signature of an aggregation of documents (payload)

- Single content creator signs entire payload- Receiver uses digital signatures to verify authenticity of content

n n Level1 - y

Authenticity Requirements 2/2Requirement Description Registration Send

eMDRSend eMD

Supports digital signature chains

- Receiver understands the order in which digital signatures were applied - Receiver understand what part of the transaction each digital signature applies to

y n y

Supports long term validation of digital signatures

- Receiver can validate digital signature up to twenty years after signing- Example: Content creator adds time-stamped and CA signed OCSP response or CRL to content at time of creation

n n y

Authority RequirementsRequirement Description Registration Send

eMDRSend eMD

Include single delegation of rights artifacts in transaction

- Party A delegates a right to Party B who may not delegate that right to any other party

n n n

Include multiple delegation of rights artifacts in transaction

- Party A delegates a right to Party B who may delegate that right to Party C

y n y

Encryption RequirementsRequirement Description Registration Send

eMDRSend eMD

Support encryption of components of payload at point of creation

- Content creator encrypts portions of the payload

n n Level 1 - n Level 3 - ?

Support encryption of entire payload at point of creation

- Content creator encrypts entire payload n n Level 1 - nLevel 2 - ?

Note: esMD assumes transport level encryption is in place. Payload encryption is still under consideration

General RequirementsCategory Requirement Description Registration Send

eMDRSend eMD

Location Security elements are included in payload

- Security elements are tied to payload and will be processed by internal systems rather than gateway

y (Delegation of Rights)

n y

Existing Standard

Created and maintained by SDO

- Uses existing standard y y y

Applicable Standard

X12 274 - Supports the exchange of provider information

y n n

Applicable Standard

IHE HPD+ - Supports the exchange of provider information

y n n

Applicable Standard

X12 277 - Supports the exchange of requests for additional information regarding a claim

n y n

Applicable Standard

X12 275 - Supports the exchange of additional information regarding a claim

n n y

Applicable Standard

HL7 CDA - Supports the exchange of patient clinical information

n n y

esMD Security Requirements Aligned to Standards by Use Case

Use Case 1: Requirements for RegistrationCategory Requirement DSG X12 58 WS-

SecurityMetadata Extension

sIdentity Include Sender's public digital certificate in

transactionn ? y y

Identity Include additional public digital certificates in transaction

y ? y y

Authenticity Supports digital signature chains ? 2? y y

Authenticity Digital Signature of entire transaction (message)

n n y n

Authority Include multiple delegation of rights artifacts in transaction

y n ? y

Authority Supports delegation of rights artifact chains ? n ? yExisting Standard Created and maintained by SDO y y y nApplicable Standard X12 274 ? y y yApplicable Standards IHE HPD+ y n y yLocation Security requirements are included in

payloady y? n y

Use Case 2: Requirements for Sending eMDRs

Category Requirement DSG X12 58 WS-Security

Metadata Extensions

Identity Include Sender's public digital certificate in transaction

y ? y y


n n y n

Existing Standard Created and maintained by SDO y y y nApplicable Standard X12 277 ? y y y

Phase 1: Requirements for Sending Electronic Medical Documentation

Category Requirement DSG X12 58 WS-Security

Metadata Extensions

Identity Include Sender's public digital certificate in transaction

y ? y y

Identity Include additional public digital certificates in transaction

y ? y y

Authenticity Supports digital signature chains ? ? y yAuthenticity Supports long term validation of digital

signaturey ? y y


n n y n

Authenticity Digital Signature of an aggregation of documents (payload)

y y/n y/n y/n

Authority Include multiple delegation of rights artifacts in transaction

y n ? y

Authority Supports delegation of rights artifact chains ? n ? yLocation Security elements are included in payload y y n nExisting Standard Created and maintained by SDO y y y nApplicable Standard X12 275 ? y y yApplicable Standard HL7 CDA y n y y

Conclusions

• No single standard/specification supports all requirements for all use cases• Support for some requirements depends on implementation details

• Example: WS-Security can sign an entire message or a portion of a message, including the payload. However, this signature would usually be processed by the SOAP gateway and unavailable to the internal information systems.

• A mix of standards may be required, each one selected to fulfill a specific requirement

Comparison of Security Standards under Review for esMD

IHE DSG

Strengths- Supports transmission of signatures and certificates- Based on XMLSig and XAdES which provides long-term validation of signatures- Can be used to sign any kind of document- XML transforms are not required- Signatures applied to payload and processed by internal system- Potentially meets AoR Level 2 requirements

Weaknesses- Receiver must track both signed document and signature document- Applicability limited to signing of documents- Probably does not meet AoR Level 3 requirements

Extensions to Metadata

Strengths- Potentially designed to meet exact needs of esMD- Signatures applied to payload and processed by internal system

Weaknesses- May require changes to existing standards- Relevant SDOs may choose to not adopt changes

Alternatives- MIME Attachments: Attach various security artifact files to payload using appropriate

MIME content-type

X12 58Strengths- Standard across all X12 transactions- Applies signature at payload level

Weaknesses- Only applicable to X12 transactions- Requires separate transaction to exchange certificates- Requires maintenance of certificates apart from transaction- No support for Delegation of Rights

WS-SecurityStrengths- Supports transmission of signatures and certificates- Easily supported in all SOAP based transactions- Based on XMLSig standard- Can support XAdES which provides long-term validation of signatures- Supports exchange of SAML Assertions (for Delegation of Rights)

Weaknesses- Signatures are applied to message and processed at gateway- Gateway would require additional configuration to pass signatures, certificates, and SAML

Assertions to internal system- No definitive specification binding SOAP over SMTP for Direct purposes

Alternatives- S/MIME: Default signing and encryption of Direct messages

Security Approach 1Message• Metadata extension contains XML Signature of message and certificate used to verify message• Metadata extension contains SAML Assertion of message and certificate used to verify message

Phase 1 Payload• IHE DSG to sign document bundle

• NwHIN/CORE: ZIP file containing document bundle and signature document placed in 275 BIN segment• Direct: ZIP file containing document bundle and signature document sent as attachment to payload

Strengths- Leverages existing standards- Supports transmission of signatures and certificates- All signatures based on XMLSig standard- Supports XAdES signature on document bundle, which provides for long-term validation of signature- Supports exchange of SAML Assertions for Delegation of Rights- Does not preclude use of X12 58 if required by trading partners

Weaknesses- Receiver must maintain attachments and track relationships between files- Approach is not completely transport neutral

esMD Transaction Process Flow by Use Case

Use Case 1: Transaction Process Flow

Registration Request

Delegation of Rights Artifact

Signature of Registration Request

Public Certificate of Registration Requestor

Assertion of Rights

Signature of Assertion

Public Certificate of Assertor

Delegation of Rights Artifact

Registration Request Message

Owner Process Standards

Registration Requestor

Request Delegation of Rights Artifact from Assertor of Rights • SAML Query

Assertor of Rights

Create Assertion • SAML

Sign Assertion and attach certificate • XMLSig

Provide Delegation of Rights Artifact to Registration Requestor • SAML Response

Registration Requestor

Create Registration Request • Payload: X12.274, HPD

Attach Delegation of Rights Artifact and attach Certificate of Subject • SAML Assertion

Sign Registration Request Message and attach certificate • XML Signature

Send Registration Request Message • NwHIN/CORE• Direct

Payer/Payer Contractor

Trace Certificate of Registration Requestor to Root CA • XML Signature

Verify Signature of Registration Request • XML Signature

Verify Delegation of Rights Artifact • SAML Assertion

Process Registration Request • Payload: X12.274, HPD

Use Case 2: Transaction Process Flow

eMDR Message

eMDR

Signature of eMDR

Public Certificate of Payer/Payer Contractor

Owner Process Standards


Create eMDR • Payload: X12.277

Sign eMDR Message and attach certificate • XML Signature

Send eMDR Message • NwHIN/CORE• Direct

eMDR Consumer

Trace Certificate of Payer/Payer Contractor to Root CA • XML Signature

Verify Signature of eMDR • XML Signature

Process eMDR • Payload: X12.277

Phase 1: Transaction Process FlowSigned Medical

Document Bundle

eMDR Response Message

eMDR Response

Document Bundle Attachment

Signature of eMDR Response

Public Certificate of eMDR Consumer

Medical Document Bundle

Signature of Document Bundle

Public Certificate of Document Bundle Owner

Owner Process Possible Locations and Standards

EHR/Provider

Assemble Medical Document Bundle • Payload: PDF, CDA, ZIP

Sign Document Bundle • Payload: DSG

Attach Public Certificate • Payload: DSG

Provide Medical Document Bundle Attachment to eMDR Consumer • Outside esMD scope

eMDR Consumer

Create eMDR Response • Payload: X12.275, XD*

Add Document Bundle Attachment • Payload: BIN Seg, Attachment

Sign eMDR Response and attach certificate • XML Signature

Send eMDR Response Message • NwHIN/CORE• Direct


Trace Certificate of eMDR Consumer to Root CA • XML Signature

Verify Signature of eMDR Response • XML Signature

Process eMDR Response • Payload: X12.275, XD*

Consume Document Bundle • Payload: DSG

Appendix: Security Dataset Requirements for both Registering to Receive eMDRs & Sending eMDRs

Signature ArtifactThe Signature Artifact (paired with the Public Digital Certificate of the Sender) will enable the message receiver to authenticate the sender, verify message integrity, and prove non-repudiation.

1. Public Digital Certificate of Sender – x.509 certificate issued by a Certificate Authority

2. Signature Artifact – Encrypted message digest*

* The exact details of the Signature Artifact are being developed in the esMD Author of Record Initiative.

Public Key of Dr. Smith

Signature Artifact Example1. Dr. Smith attaches signature artifact to Request to Register to Receive eMDRs


Provider Name: Dr. SmithNPI: 987654Service: Receive eMDRs

MetadataEncrypted Message Digest: H8K9QTPPublic Digital Certificate of Dr. Smith

hash function Message Digest: 987654 signature algorithm

Private Key of Dr. Smith

2. Payer verifies the Request came from Dr. Smith and has not been tampered with


Provider Name: Dr. SmithNPI: 987654Service: Receive eMDRs

MetadataEncrypted Message Digest: H8K9QTPPublic Digital Certificate of Dr. Smith

hash function Message Digest: 987654

signature algorithm

Verify Identity

Message Digest: 987654

Verify Integrity

Delegation of Rights ArtifactThe Delegation of Rights Artifact (paired with the Public Digital Certificate of Subject) enables the Subject to delegate a right to the Sender of a Request such that the Receiver can cryptographically confirm that delegation of rights has occurred.

1. Public Digital Certificate of Subject – x.509 certificate issued by a Certificate Authority

2. Delegation of Rights Artifact – Encrypted message digest of an assertion of rights*

* The exact details of the Delegation of Rights Artifact are being developed in the esMD Author of Record Initiative.

Delegation of Rights Example (1/2)1. Dr. Smith delegates the right to register his NPI to receive eMDRs to Medical Data, Inc.


Provider Name: Dr. Bob SmithNPI: 987654Service: Receive eMDRsMetadataEncrypted Message Digest: H8K9QTPPublic Digital Certificate of Medical Data, Inc.Delegation of Rights ArtifactPublic Digital Certificate of Dr. Smith

2. Medical Data, Inc. include their Signature Artifact, Dr. Smith’s Delegation of Rights Artifact, and both Public Digital Certificates in their Request to Register Dr. Smith to Receive eMDRs

Assertion of Rights

Dr. Bob Smith gives Medical Data, Inc. the right to register his NPI to receive eMDRs.Expiration Date: 1/1/2013

MetadataEncrypted Message Digest: U37G90P

hash function Message Digest: 123456 signature algorithm

Private Key of Dr. Smith

Delegation of Rights Example (2/2)


Provider Name: Dr. Bob SmithNPI: 987654Service: Receive eMDRsMetadataEncrypted Message Digest: H8K9QTPPublic Digital Certificate of Medical Data, Inc.Delegation of Rights ArtifactPublic Digital Certificate of Dr. Smith

3. Payer verifies Medical Data, Inc. has the right to register Dr. Smith to receive eMDRs

Public Key of Dr. Smith

Assertion of Rights

Dr. Bob Smith gives Medical Data, Inc. the right to register his NPI to receive eMDRs.Expiration Date: 1/1/2013

MetadataEncrypted Message Digest: U37G90P

hash function Message Digest: 123456

signature algorithm Message Digest: 123456

Verify Right

alternatives for message signature from sender

Documents