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Transfer dIGital cREdentialS Securely
charter-ietf-tigress-01

Document Charter Transfer dIGital cREdentialS Securely WG (tigress)
Title Transfer dIGital cREdentialS Securely
Last updated 2022-07-19
State Approved
WG State Active
IESG Responsible AD Roman Danyliw
Charter edit AD Roman Danyliw
Send notices to (None)

charter-ietf-tigress-01

There are many situations in which it is desirable to transfer a copy of a digital credential to another person. For example, a private car owner may want to provide access to their vehicle to a friend or a family member. A private homeowner may want to provide access to their home to their cat sitter. An individual staying at a hotel may want to transfer a copy of a hotel room key to their spouse. Today, no such standardized method exists in a cross-platform, credential type-agnostic capacity.

The WG will standardize a protocol that will facilitate such credential transfers from one person's device to another person's device. The protocol will leverage a "relay server" to transfer data from sender to recipient. The scope of the transfer is limited to a single origin device and a single destination device. Note: neither private keys nor secret symmetric keys present on the sender's device are exchanged during the transfer operation. In the transfer protocol, the “credential” is the information issued by a credential authority for a given user and device that allows them to have access rights to a certain asset. The “share” is a data structure transferred from the sender to recipient that comprises the data both necessary and sufficient for the recipient to request a new credential from the credential authority to provision it to the receiving device.

Privacy goals include:

  • The relay server should not see sensitive details of the share

  • The relay server should not be able to provision the credential itself, acting as an intermediary for the recipient (person-in-the-middle, impersonation attack)

  • Aside from network-level metadata, the relay server should not learn information about the sender or receiver

Sufficient security measures should be embedded in the protocol in an effort to:

  • Ensure only the intended recipient is able to provision the credential

  • Ensure the credential can only be provisioned once (anti-replay)

  • Ensure the sender has the intent to transfer (proof of the fact that the share initiation is attributed to a valid device and a user)

The solution the WG defines is expected to:

  • Allow a sender to initiate a share and select a relay server

  • Allow a recipient to view the share request, and provision the credential associated with the share upon receipt

  • Allow a sender and a recipient to perform multiple round trip communications within a limited time frame

  • Not require that both the sender and recipient have connectivity to the relay server at the same time

  • Support opaque message content based on the credential type

  • Support a variety of types of credentials, to include those adhering to public standards (e.g., Car Connectivity Consortium) and proprietary (i.e., non-public or closed community) formats

The following topics are out of scope for the WG:

  • Defining the mechanism the receiver will use in order to provision the credential with the credential authority

  • The User Interface (UI) that is displayed to the sender or receiver during sending or receiving (this will depend on the device manufacturer's interface guidelines)

  • Defining the format or content of each field within the encrypted data (i.e., the provisioned credentials and associated information) stored on the relay server

The WG will deliver a protocol to facilitate secure credential transfer. The WG must consider all Privacy and Security goals in an effort to perform the credential transfer securely. The protocol will use appropriate cryptographic mechanisms to protect the transferred credentials in accordance with the security and privacy goals described above.