PKI Certificate Identifier Format for DevicesCiscoofriel@cisco.comCiscorlb@ipv.sxThis document defines a standard Subject field identifier format for certificates issued to Internet of Things (IoT) devices. This will allow applications to easily and uniquely identify certificates issued to devices as opposed to certificates issue to services or users. The certificates will adhere to standard Web PKI specifications thus ensuring interoperability with existing Certificate Authorities processes and workflows, and standard client and service libraries and applications.There is an increasing need for devices to be able to uniquely identify themselves and assert their identity, and associated identity attributes, using standard Web PKI techniques. In order to faclitate issuing certificates to devices, this document defines a mechanism for uniquely identifying devices using a structured Subject field identifier that should be supported by all major Certificate Authorities (CAs), including those CAs that support .The use of Web PKI for the purpose of issuing device certificates has multiple benefits including:Existing code, processes, and policies for managing Web PKI certificates can be re-usedDevice certificates can be trusted by web browsersFor small-scale device manufacturers, it is possible to use existing CAs to issue device certificates of this kindFor more mature manufacturers, the use of structured DNS names to encode device information means that name-constrained intermediate CAs can be used to allow the manufacturer to issue device certificates independently of the root CA.Previous attempts to uniquely identify device certificates have not proven to be broadly supported by common certificate management software libraries. These include: which defines a serialNumber field which defines a hardwareModuleName fieldDevices will typically have a unique certificate that is baked into the device at manufacturing time i.e. the device will leave the factory with a unique manufacturer installed certificate already baked in. This certificate will typically be signed by a CA that the manufacturer controls, or a CA that the manufacturer explicitly authorizes. This CA does not necessarily have be a public root CA that is trusted by web browsers. This certificate is referred to as the Initial Device Identifier (IDevID).A common deployment requirement is that the end customer that purchases and deploys the device in their local domain will need to install a certificate on the device that is signed by a CA under their control, or signed by a CA of their choosing. This certificate is referred to as the Locally Significant Device Identifier (LDevID).A unique device identifier is encoded in a structured Device Information Domain Name Identifier (DIDN-ID) of the following form:where keyword MUST be one of:The fields serial, model and domain are described in the following sections.IDevID certificates have the following form:Where:manufacturer is a fully-qualified domain name identifying the manufacturer of the device_mDevice is a mandatory keyword that indicates this is an IDevID installed at manufacturing timemodel is a manufacturer-chosen string that MUST identify the model or type of the deviceserial is a manufacturer-chosen string that MUST identify the specific serial number of this modelThe combination of manufacturer, model, and serial MUST uniquely identify the device.If the LDevID is issued by a public trusted CA, then the LDevID idenfitier format MUST follow the identifier format specified in this section.Where the LDevIDs are issued by private domain CAs that do not necessarily need to adhere to CA/Browser forum guidelines, it is strongly recommended that the private CA follows this identifier format specification.LDevID certificates have the following form:Where:deployment-domain is a fully-qualified domain name identifying the local domain where the device is installed. This will typically be a domain that the purchaser or owner of the device can assert ownership of_device is a mandatory keyword that indicates this is an LDevID installed during live deploymentmodel this SHOULD be copied from the IDevID of the deviceserial this SHOULD be copied from the IDevID of the deviceThe combination of manufacturer, model, and serial SHOULD uniquely identify the device.If the customer who owns the device uses a public CA to issue the LDevID, and if the device serial number and/or model is considered sensitive or Personally Identifiable Information (PII), then the serial and model fields MAY be replaced with suitable alternate identifiers. However, the public CA MUST ensure that the format and structure of the DIDN-ID adheres to this specification.Following the recommendations set out in , the Subject field of the certificate MAY contain the commonName field, set to the DIDN-ID for the device.The Subject field MAY also contain a serialNumber or hardwareModuleName field.The certificate MUST contain a subjectAltName extension contataining a single dnsName entry with the DIDN-ID for the device.The certificate MUST contain an extKeyUsage extension with the values id-kp-serverAuth and id-kp-clientAuth, and no other values.IDevID certificates with _mDevice identifiers in their DIDN-ID MUST have a notAfter value of 99991231235959Z (i.e. Y10K).It should be noted that at the time of writing, web browsers do not check for Y10K and will happily establish connections with endpoints whose identity certificate has a notAfter value of Y10K.LDevID certificates are issued during live deployment and MUST follow the standard lifetime and expiration requirements of the issuing CA.[[ TODO: Register the _device and _mDevice labels ]][[ TODO ]]Secure Device IdentityIEEEAutomatic Certificate Management Environment (ACME)Certificates in PKI using X.509 (PKIX) are used for a number of purposes, the most significant of which is the authentication of domain names. Thus, certificate authorities in the Web PKI are trusted to verify that an applicant for a certificate legitimately represents the domain name(s) in the certificate. Today, this verification is done through a collection of ad hoc mechanisms. This document describes a protocol that a certification authority (CA) and an applicant can use to automate the process of verification and certificate issuance. The protocol also provides facilities for other certificate management functions, such as certificate revocation.Using Cryptographic Message Syntax (CMS) to Protect Firmware PackagesThis document describes the use of the Cryptographic Message Syntax (CMS) to protect firmware packages, which provide object code for one or more hardware module components. CMS is specified in RFC 3852. A digital signature is used to protect the firmware package from undetected modification and to provide data origin authentication. Encryption is optionally used to protect the firmware package from disclosure, and compression is optionally used to reduce the size of the protected firmware package. A firmware package loading receipt can optionally be generated to acknowledge the successful loading of a firmware package. Similarly, a firmware package load error report can optionally be generated to convey the failure to load a firmware package. [STANDARDS-TRACK]Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS)Many application technologies enable secure communication between two entities by means of Internet Public Key Infrastructure Using X.509 (PKIX) certificates in the context of Transport Layer Security (TLS). This document specifies procedures for representing and verifying the identity of application services in such interactions. [STANDARDS-TRACK]