Merge pull request #1838 from jimfenton/aal-consistency

AAL consistency and TEEs

Author: Paul Grassi

sp800-63-3/cover.md

@@ -200,7 +200,7 @@ These guidelines are organized as follows:
 
 SP 800-63 provides an overview of general identity frameworks, using authenticators, credentials, and assertions together in a digital system, and a risk-based process of selecting assurance levels. _SP 800-63 contains both normative and informative material._
 
-[**SP 800-63A Enrollment and Identity Proofing**](https://pages.nist.gov/800-63-3/sp800-63a.html)
+[**SP 800-63A Enrollment and Identity Proofing**](sp800-63a.html)
 
 NIST SP 800-63-A addresses how applicants can prove their identities and become enrolled as valid subscribers within an identity system. It provides requirements by which applicants can both proof and enroll at one of three different levels of risk mitigation in both remote and physically-present scenarios. _SP 800-63A contains both normative and informative material._
 
@@ -213,19 +213,19 @@ SP 800-63A sets requirements to achieve a given IAL. The three IALs reflect the
 **IAL3** - Physical presence is required for identity proofing. Identifying attributes must be verified by an authorized and trained representative of the CSP. As with IAL2, attributes can be asserted by CSPs to RPs in support of pseudonymous identity with verified attributes.
 
 
-[**SP 800-63B Authentication and Lifecycle Management**](https://pages.nist.gov/800-63-3/sp800-63b.html)
+[**SP 800-63B Authentication and Lifecycle Management**](sp800-63b.html)
 
 For services in which return visits are applicable, a successful authentication provides reasonable risk-based assurances that the subscriber accessing the service today is the same as that which accessed the service previously. The robustness of this confidence is described by a categorization known as the AAL. NIST SP 800-63B addresses how an individual can securely authenticate to a CSP to access a digital service or set of digital services. _SP 800-63B contains both normative and informative material._
 
 The three AALs define the subsets of options agencies can select based on their risk profile and the potential harm caused by an attacker taking control of an authenticator and accessing agencies' systems. The AALs are as follows:
 
-**AAL1** - AAL1 provides some assurance that the claimant controls an authenticator registered to the subscriber. AAL1 requires single-factor authentication using a wide range of available authentication technologies. Successful authentication requires that the claimant prove possession and control of the authenticator through a secure authentication protocol.
+**AAL1** - AAL1 provides some assurance that the claimant controls an authenticator bound to the subscriber's account. AAL1 requires either single-factor or multi-factor authentication using a wide range of available authentication technologies. Successful authentication requires that the claimant prove possession and control of the authenticator through a secure authentication protocol.
 
-**AAL2** - AAL2 provides high confidence that the claimant controls authenticator(s) registered to the subscriber. Proof of possession and control of [two distinct authentication factors](#mfa-definition) is required through secure authentication protocol(s).  [Approved cryptographic](#approved) techniques are required at AAL2 and above.
+**AAL2** - AAL2 provides high confidence that the claimant controls authenticator(s) bound to the subscriber's account. Proof of possession and control of [two distinct authentication factors](#mfa-definition) is required through secure authentication protocol(s). [Approved cryptographic](#approved) techniques are required at AAL2 and above.
 
-**AAL3** - AAL3 provides very high confidence that the claimant controls authenticator(s) registered to the subscriber. Authentication at AAL3 is based on proof of possession of a key through a cryptographic protocol. AAL3 is like AAL2 but also requires a "hard" cryptographic authenticator that provides verifier impersonation resistance.
+**AAL3** - AAL3 provides very high confidence that the claimant controls authenticator(s) bound to the subscriber's account. Authentication at AAL3 is based on proof of possession of a key through a cryptographic protocol. AAL3 authentication SHALL use a hardware-based cryptographic authenticator and an authenticator that provides verifier impersonation resistance; the same device MAY fulfill both these requirements. In order to authenticate at AAL3, claimants SHALL prove possession and control of [two distinct authentication factors](#mfa-definition) through secure authentication protocol(s). [Approved cryptographic](#approved) techniques are required.
 
-[**SP 800-63C Federation and Assertions**](https://pages.nist.gov/800-63-3/sp800-63c.html)
+[**SP 800-63C Federation and Assertions**](sp800-63c.html)
 
 NIST SP 800-63C provides requirements when using federated identity architectures and assertions to convey the results of authentication processes and relevant identity information to an agency application. In addition, this guideline offers privacy enhancing techniques to share information about a valid, authenticated subject, as well as describing methods that allow for strong multi-factor authentication (MFA) while the subject remains pseudonymous to the digital service. _SP 800-63C contains both normative and informative material._
 

sp800-63-3/definitions.md

@@ -255,7 +255,7 @@ A characteristic of an authentication system or an authenticator that requires m
 
 The three authentication factors are something you know, something you have, and something you are.
 
-#### <a name=”mfa-definition”></a>Multi-factor Authentication (MFA)
+#### <a name="mfa-definition"></a>Multi-factor Authentication (MFA)
 An authentication system that requires more than one distinct [authentication factor](#af) for successful authentication. Multi-factor authentication can be performed using a multi-factor authenticator or by a combination of authenticators that provide different factors.
 
 The three authentication factors are *something you know*, *something you have*, and *something you are*.
@@ -352,7 +352,7 @@ Credentials that describe the binding in a way that does not compromise the auth
 The public part of an asymmetric key pair that is used to verify signatures or encrypt data.
 
 #### Public Key Certificate
-A digital document issued and digitally signed by the private key of a certificate authority that binds an identifier to a subscriber to a public key. The certificate indicates that the subscriber identified in the certificate has sole control and access to the private key. See also [[RFC 5280]](https://pages.nist.gov/800-63-3/sp800-63b.html#RFC5280).
+A digital document issued and digitally signed by the private key of a certificate authority that binds an identifier to a subscriber to a public key. The certificate indicates that the subscriber identified in the certificate has sole control and access to the private key. See also [[RFC 5280]](sp800-63b.html#RFC5280).
 
 #### Public Key Infrastructure (PKI)
 A set of policies, processes, server platforms, software, and workstations used for the purpose of administering certificates and public-private key pairs, including the ability to issue, maintain, and revoke public key certificates.

sp800-63b/sec4_aal.md

@@ -54,7 +54,7 @@ The CSP shall comply with its respective records retention policies in accordanc
 
 ### 4.2 Authenticator Assurance Level 2
 
-AAL2 provides high confidence that the claimant controls authenticator(s) bound to the subscriber's account. Proof of possession and control of [two distinct authentication factors](#mfa-definition) is required through secure authentication protocol(s). [Approved cryptographic](#approved) techniques are required at AAL2 and above.
+AAL2 provides high confidence that the claimant controls authenticator(s) bound to the subscriber's account. Proof of possession and control of [two distinct authentication factors](sp800-63-3.html#mfa-definition) is required through secure authentication protocol(s). [Approved cryptographic](sp800-63-3.html#approved) techniques are required at AAL2 and above.
 
 #### <a name="aal2types"></a>4.2.1 Permitted Authenticator Types
 
@@ -100,11 +100,11 @@ The CSP SHALL employ appropriately-tailored security controls from the moderate
 
 #### <a name="aal2records"></a> 4.2.5 Records Retention Policy
 
-The CSP shall comply with its respective records retention policies in accordance with applicable laws, regulations, and policies, including any National Archives and Records Administration (NARA) records retention schedules that may apply. If the CSP opts to retain records in the absence of any mandatory requirements, the CSP SHALL conduct a risk management process, including asessements of privacy and security risks to determine how long records should be retained and SHALL inform the subscriber of that retention policy. 
+The CSP shall comply with its respective records retention policies in accordance with applicable laws, regulations, and policies, including any National Archives and Records Administration (NARA) records retention schedules that may apply. If the CSP opts to retain records in the absence of any mandatory requirements, the CSP SHALL conduct a risk management process, including assessements of privacy and security risks to determine how long records should be retained and SHALL inform the subscriber of that retention policy. 
 
 ### 4.3 Authenticator Assurance Level 3
 
-AAL3 provides very high confidence that the claimant controls authenticator(s) bound to the subscriber's account. Authentication at AAL3 is based on proof of possession of a key through a cryptographic protocol. AAL3 authentication SHALL use a hardware-based cryptographic authenticator and an authenticator that provides verifier impersonation resistance; the same device MAY fulfill both these requirements. In order to authenticate at AAL3, claimants SHALL prove possession and control of [two distinct authentication factors](#mfa-definition) through secure authentication protocol(s). [Approved cryptographic](#approved) techniques are required.
+AAL3 provides very high confidence that the claimant controls authenticator(s) bound to the subscriber's account. Authentication at AAL3 is based on proof of possession of a key through a cryptographic protocol. AAL3 authentication SHALL use a hardware-based cryptographic authenticator and an authenticator that provides verifier impersonation resistance; the same device MAY fulfill both these requirements. In order to authenticate at AAL3, claimants SHALL prove possession and control of [two distinct authentication factors](sp800-63-3.html#mfa-definition) through secure authentication protocol(s). [Approved cryptographic](sp800-63-3.html#approved) techniques are required.
 
 #### <a name="aal3types"></a>4.3.1 Permitted Authenticator Types
 

sp800-63b/sec5_authenticators.md

@@ -119,7 +119,7 @@ The out-of-band device SHOULD be uniquely addressable and communication over the
 
 The out-of-band authenticator SHALL uniquely authenticate itself in one of the following ways in communicating with the verifier:
 
-- Establish an authenticated protected channel to the verifier using approved cryptography. The key used SHALL be stored in suitably secure storage available to the authenticator application (e.g., keychain storage, trusted platform module, secure element).
+- Establish an authenticated protected channel to the verifier using approved cryptography. The key used SHALL be stored in suitably secure storage available to the authenticator application (e.g., keychain storage, trusted platform module, secure element, trusted execution environment).
 
 - Authenticate to a public mobile telephone network using a SIM card or equivalent that uniquely identifies the device. This method SHALL only be used if a secret is being sent from the verifier to the out-of-band device via the PSTN (SMS or voice).
 
@@ -477,4 +477,4 @@ Furthermore, the risk of an authentication error is typically borne by multiple
 
 3. Address any additional risk to subscribers in its risk assessment.
 
-4. Develop a migration plan for the possibility that the RESTRICTED authenticator is no longer acceptable at some point in the future and include this migration plan in its [digital identity acceptance statement](https://pages.nist.gov/800-63-3/sp800-63-3.html#daps).
+4. Develop a migration plan for the possibility that the RESTRICTED authenticator is no longer acceptable at some point in the future and include this migration plan in its [digital identity acceptance statement](sp800-63-3.html#daps).