The following generalised functional units (actions) serve to design and implement the vetting scenarios for second factor and multifactor authentication that fulfil some of ITU-T X.1254 entity authentication assurance framework processes. The following processes from its "8.1 Enrollment phase" are to be covered:

• 8.1.1 Application and initiation
  
• 8.1.2 Identity proofing and identity information verification
  
• 8.1.3 Record-keeping/recording
  

"8.1.4 Registration" is omitted as it is related with (later) use of services or resources.

Of all processes described in "8.2 Credential management phase" - only these are addressed here, as they are related with initialisation and issuance of the authentication factors, which, in our scenarios, are closely tied to identity proofing and verification:

• 8.2.1 Credential creation
  
  • 8.2.1.1 Credential pre-processing
    
  • 8.2.1.2 Credential initialization
    
  • 8.2.1.3 Credential binding
    
• 8.2.2 Credential issuance
• 8.2.3 Credential activation
• 8.2.7 Record-keeping
  

The names and descriptions used in these elaborations aim to be mappable to those processes and be terminologically compatible with ITU-T X.1254 and its definitions of terms. An additional specifics in relation the above-listed processes is that they focus on the credentials (sets of data supporting identity or entitlement claims), while our scenarios are focused on authentication factors (something specific that is possessed, known or inherent). The subject entities are referred to as applicants, who are the physical persons whose identity is to be authenticated.

C: Commons

The actions listed here are common actions which may be used at multiple times at different stages and for various purposes. These actions are:

• Use Exiting Factor
• Select New Factor
• Use Introduced Factor
• Eligibility check

C_USE_EXISTING_FACTOR Authenticate Existing Factor

The applicant authenticates with his/her existing factor(s). Username/password login is typically the first existing factor that is readily available.

This action may be used for multiple purposes:

Perform authentication with the existing factor(s) to prove knowledge/possession of the respective factor(s).

This action may also be used for checking the applicants eligibility (see C_CHECK_ELIGIBILITY) based on the credentials used (e.g. by searching for a name or e-mail address in a LDAP directory) or the attributes (e.g. affiliation) which are send in the authentication response.

Input: Credentials (e.g. username/password combination, certificate)

Output: Authentication successful (yes/no), attributes is needed (e.g. affiliation)

C_SELECT_NEW_FACTOR

The applicant selects the type of the new factor to be introduced if there are several options. The offered options may depend on the place of the use, for example, a wider set of options may be available during initiation than with a particular vetting the user was directed to at the initiation phase.

There may be different factor types, e.g. something you know/have/are, the applicant can choose from as well as multiple realization options/products per factor (e.g. Yubikey, Google Authenticator).

Input: List of possible factors

Output: factor selected/assigned and known (or) in possession/... by the applicant

C_USE_NEW_FACTOR Use Introduced Factor

Usage of the introduced factor may serve multiple purposes at different stages.

E.g. Use introduced factor to test functioning, to prove knowledge/possession/inheritance/... or to make sure factors match.

Input: new factor

Output: usage of factor took place (for various purposes)

C_CHECK_ELIGIBILITY Check Eligibility of Applicant

Check if the applicant is eligible to request an additional factor. For example, if there are some policy or contractual restrictions. Is the applicant associated with participating organisation and eligible for the offered delivery of the additional physical factor such as token?

Done by manual or automated check a directory, federated identity, or examination of a written institutional certificate.

Input: applicant's identifying information

Output: decision: eligible (yes/no)

I: Application and Initiation

Initial request for an additional authentication factor during which vetting arrangements are made. Optional actions in case face-to-face vetting will take place. If needed:

• Merge REQUEST_FACTOR and FACTOR_DELIVERY?
• Arrange Vetting

C_USE_EXISTING_FACTOR (optional) DEFINED IN C

Optional. Used to provide both information about user identity and initial proof (with presumably weaker assurance) that the applicant is who (s)he claims to be.

C_CHECK_ELIGIBILITY (optional, requiring C_USE_EXISTING_FACTOR) DEFINED IN C

Optional. Used to check whether the applicant is entitled to request the additional factor at the moment of application, as this may incur some costs or use of resources.

C_SELECT_NEW_FACTOR (optional) DEFINED IN C

Optional, if there are several options for factors that may be offered at the start. May affect the options to be used during the vetting phase.

I_REQUEST_FACTOR

Optional. The applicant may also provide a delivery address and perhaps even pay for the factor, handling and delivery service. This may be even as simple as redirection to the external factor provider.

I_FACTOR_DELIVERY

Optional sending or handing over of the physical factor (typically a token), if such is used, and if this is a part of the provided service.

C_USE_NEW_FACTOR (optional) DEFINED IN C

Optional factor (token) preregistration and binding with the request. If the applicant is expected to possess a token at the time of registration; alternatively, this can be done during the vetting phase.

I_ARRANGE_VETTING (optional)

Optional detailing of vetting. E-mail, initiation application or other channel is used to communicate a code, appointment details or other relevant information. May include several steps:

• Creation of a (secret) code to be used at the start of vetting procedure to identify the vetting request or the new factor used during initiation (C_USE_NEW_FACTOR).
• If e-mail is used for vetting arrangement, get applicant's e-mail address (e.g. from the IdP account data) or from the applicant.
• Optional location selection and/or scheduling of the vetting appointment, only if the load or the policy of the service (desk) require this.
• Provide vetting details over e-mail or through the application, with written or QR code, email validation link, instructions, vetting application link, service desk contacts, address and appointment details, and whatever else is needed.
• Optional e-mail validation, if e-mail is required for further interaction, and if a valid e-mail address is not already accessible and assured/guaranteed from the IdP data provided upon the previously performed login with the existing factor.

V: Identity Proofing and Information Verification

Do the actual vetting by proofing the applicant's identity and verifying identity information.

• Proof
• Liveness
• Source
• Record
  

V_COMMENCE Begin vetting, possibly by accessing and validating the prior request

Set up the context for identity proofing and information verification by linking prior initiation or performing it if has not been done. Verify, resume, and potentially update the context established during the initiation, or do the key work that that is in it. For example, if the applicant is allowed to come to a service desk without prior registration, the key elements of the initiation still must be performed, such as C_CHECK_ELIGIBILITY and C_SELECT_NEW_FACTOR; other initiation elements related to scheduling of the appointment or linking of initiation and vetting, such as (secret) code creation are pointless, as the applicant is already present and available for vetting.

• Vetting may be rejected and applicant turned back if the application is not eligible or if the queue is too long or the necessary resources, staff or involved key services are not available at this point.
• Restoring of the information and context established during initiation may include C_USE_EXISTING_FACTOR or use of previously created code to identify the vetting request or the factor used during initiation.
• If the validity of e-mail address is considered significant, a code or link may be used to make sure that the applicant's e-mail is valid and can be accessed by her.
• This may done by the applicant or by the service or operator check of the code issued during the initiation and that is now provided by the applicant. The code is used to link the applicant with the original application, it is particularly useful when the applicant does not possess or know the first factor and is not able to perform C_USE_EXISTING_FACTOR.
• If some time has passed since initiation, it may be necessary to perform C_CHECK_ELIGIBILITY again, as the applicant situation with her organisation may have changed in the meantime. This check could be done based on performed C_USE_EXISTING_FACTOR or the verbally provided identifying information, which, in the case of human-to-human interaction may be a softer start of vetting than to immediately demand V_PRESENT_PROOF.

V_CREATE_DIGITAL_IDENTITY (optional)

Only if the applicant does not already possess the IdP identity (weak or 1st factor identity). This is optional and often prohibited or discouraged and avoided except for those in need of assistance or VIP individuals. Usually done before V_VERIFY_IDENTITY in order to allow parallelism at the service desk; should be undo-able if V_VERIFY_IDENTITY fails. This includes the check of the alignment with the enforced policies, informing of the applicant about the rules associated with this factor, creation of the username and the password, and providing the applicant with them.

This action should be invalidated if any of the following enrollment actions fails during both vetting and binding phases.

V_PRESENT_PROOF → include in V_VET_PROOF?

The applicant presents proof of identity, typically a sanctioned type of picture ID doc with demographic and biometric data.

C_SELECT_NEW_FACTOR (optional) DEFINED IN C

Optional - change of the factor the applicant has already applied for is quite unlikely but this may offer some flexibility by modifying the original choice made during the initiation.

V_HAND_OVER_FACTOR → refer to I_FACTOR_DELIVERY?

Optional, if the factor such as token is provided by the service desk. Recording of handover is probably unnecessary, as the service/operator is in the possession a proof (it was obtained with V_PRESENT_PROOF), so there is no risk of an irremediable situation or that the applicant would flee with the factor before C_USE_NEW_FACTOR.

V_VERIFY_IDENTITY →do we need subactions here?

Detailed check of ID validity and match with the person of the applicant. Compare the claimed identity (information) which is transmitted by the applicant or system with the applicant's identity proof and the actual person.

• V_VET_ PROOF The applicant presents proof of identity, typically a sanctioned type of picture ID doc with demographic and biometric data.  Then reading and inspecting the ID doc, compare the name with the vetting request, check ID security features, optionally electronically read the ID doc, optionally externally check doc validity, compare photo/biometrics match with the person.

V_SOURCE (optional)

Check user's identity proof (e.g. national ID document, employee ID card) against its original source for validity.

Make sure the identity proof is not expired/revoked/invalid/...

Input: user's identity proof

Output: verified identity proof

Effect on LoA: typically higher LoA require this action

• V_CHECK_LIVENESS (optional) Perform Liveness Check
  

In case online identity vetting mechanisms are used (such as video identification, online document upload) a liveness check may be performed to prevent fraud. Otherwise implied by V_VET_ PROOF conducted with the user.

Example1: Show ID document besides the head to prove ID document and holder match.

Example2: Upload ID document and real-time recorded selfie.

Input: any means that show liveness

Output: liveness verified

• V_RECORD_PROOF_AUDIT_DATA (optional) Record Identity Proof

Optional, typically by recording the last digits of ID doc number (avoid recording excess personal data, photos of the person or ID doc)

For accountability purposes (parts of) the identity proof (e.g. last 6 digits of national ID document) is recorded.

Input: identity proof

Output: record

Effect on LoA: not applicable

C_USE_NEW_FACTOR (optional) DEFINED IN C

Making sure that the applicant knows/possesses/inherits the new factor and is able to use it. Or in case of preregistration make sure that the factors match. This could be done by the user in parallel with V_VERIFY_IDENTITY. It may be preceded with C_USE_EXISTING_FACTOR it if has not been already performed. This may be avoided if C_USE_NEW_FACTOR was done during initiation or implied by a record on V_HAND_OVER_FACTOR. The record about C_USE_NEW_FACTOR could be a standalone event of the vetting phase or even required if there was no V_HAND_OVER_TOKEN, but it may be unnecessary with the presence C_PREREGISTER_TOKEN and V_USE_VETTING_CODE; the used token will be later bound to digital identity.

V_PREREGISTER_FACTOR (optional) → this is no preregistration, rather POSTregistration

This factor will be later bound and activated, so the record about it and its association with the applicant's digital identity is saved. For this to happen, all prior steps of vetting should be completed with success.

B: Factor Binding and Activation

Establishment of an operational link between the identity of the user and factor.

• Binding of factor and ID
  
• Activation
• Confirmation

B_FACTOR_AND_ID Bind factor to ID

Create a long term binding between the introduced factor and the digital ID of the user based on verified user identity.

Input: verified user identity, digital ID of user, factor

Output: binding between digital ID and factor

B_ACTIVATE Activate Binding of Digital ID and New Factor

Activate the binding of the digital ID of the user and the new factor. Explain why activation is needed after binding...

Input: binding between digital ID and factor

Output: decision: activation successful/unsuccessful

B_CONFIRMATION Inform User about Factor Activation

Inform the user about the correct/incorrect activation of the factor.

In case the factor activation was successful, the applicant can now authenticate using more than one factor.

Input: result of factor activation (positive/negative)

Output: message to the applicant

------------------------------------------------------ Template for providing example realization options ---------------------------------------------------------------------

could consider more attributes such as:

Likely to be mandatory in MFA: (yes/no)
Risks if omitted: (mostly security-related)
Effect on level of assurance: (how it increases, decreases LoA)
+
Other potential technical concerns/issues
Potential organisational (IP, NREN, GEANT) concerns/issues
Potential end-user concerns/issues

Example realization options

	2FA token request	2FA token (pre-)registration		Identification				Token binding
	1.1) User provides user info	2.1) User selects 2FA token	2.2) User performs authentication with that token to prove possession	3.1) Eligibility check of user	3.2) Vet identity of user			4.1) User chooses own token or handover of token to user	4.2) Bind token to digital ID	4.3) Token-proof-of-possession	4.4) Token activation & record	4.5)Inform user
					3.2.1) Compare claimed/transmitted/spoken information with user's identity proof	3.2.2) Check user's identity proof with its original source for validity	3.2.3) Record identity proof
Method
Live video	federated login			(checked in 1.1 via login)
...