| Internet-Draft | tigress-requirements | November 2022 |
| Vinokurov, et al. | Expires 13 May 2023 | [Page] |
This document describes the use cases necessitating the secure transfer of digital credentials, residing in a digital wallet, between two devices and defines general assumptions, requirements and the scope of the corresponding Tigress Internet-draft [Tigress-00].¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://datatracker.ietf.org/doc/draft-tigress-requirements/. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-tigress-requirements/.¶
Source for this draft and an issue tracker can be found at https://github.com/dimmyvi/tigress-requirements.¶
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Today, there is no widely accepted way of transferring digital credentials securely between two digital wallets independent of hardware and software manufacturer. This document describes the problem space and the requirements for the solution the working group creates.¶
Tigress allows for a sender and receiver to communicate in order to facilitate a secure credential transfer between two digital wallets. Tigress also specifies certain privacy requirements in order to maintain a high level of user privacy.¶
When sharing digital secure credentials, there are several actors involved. While the Tigress working group's solution will focus on sharing information between two digital wallets, potentially through an intermediary server, there are a couple more actors involved.¶
The companies that are providing the digital credential for consumption by a digital wallet are the provisioning partners. They are in control of the provisioning information and the lifecycle of the credentials. Each digital wallet has a preexisting trust relationship between itself and the Provisioning Partner.¶
The interface between the devices and the Provisioning Partner can be proprietary or a part of published specifications such as the [CCC-Digital-Key-30]. The sender obtains provisioning information from the provisioning partner, then shares it to the recipient via Tigress. The recipient then takes that data and sends it to the Provisioning Partner to redeem a credential for consumption in a digital wallet.¶
For some credential types the Provisioning Partner who mints new credentials is actually the sender. In that scenario the receiver will generate a new key material at the request of the sender, and then communicate with the sender over Tigress to have its key material signed by the sender.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
General terms:¶
mermaid
sequenceDiagram
actor S as Sender
participant I as Intermediary
actor R as Receiver
S ->> I : upload credential data
break Generic messaging channel
S ->> R : send invite
end
Loop Provision credential
R ->> I : request credential data
I ->> R : deliver credential data
end
¶
If the solution requires an intermediary server, it should have the following requirements.¶
A number of existing solutions / protocols have been reviewed in order to be used for secure credential transfer based on the requirements: GSS-API, Kerberos, AWS S3, email, Signal. None of the existing protocols comply with the requirements; the effort of modifying the existing protocols has been accessed to be significantly higher than introducing a new solution to solve this problem. The goal of the Tigress draft [Tigress-00] is not to define a new encryption or secure message exchange protocol, but rather a standardized mechanism of exchanging access-specific encrypted credential information.¶
The Provisioning Information MAY be sent from Sender to Receiver over an arbitrary messaging channel that supports binary file transfer, but this would not support provisioning flows which require multiple round trips as requied by (Req-RoundTrips). The same requirement applies to Signal protocol outside of the Signal app, as the Req-RoundTrips would likely be difficult and add a lot of friction for the user.¶
GSS-API [RFC2078] and Kerberos [RFC4120] are authentication technologies which could be used to authenticate Sender, Receiver and intermediary. However, as they provide strong authentication, they would allow the Intermediary server to build a social graph in violation of (Req-Privacy). Their setup also require strong coordination between the actors of the system which seems overly costly for the intended system. AWS S3 could be used as an Intermediary server but it would force all participants to use a specific cloud service which is in violation of (Req-AnyPlatorm).¶
TODO Security¶
This document has no IANA actions.¶
TODO acknowledge.¶