Anonymous Bot Authentication: Authorization and Rate Limiting for Web Agents
draft-rescorla-anonymous-webbotauth-00
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draft-rescorla-anonymous-webbotauth-00
Network Working Group E. Rescorla
Internet-Draft Independent
Intended status: Informational R. L. Barnes
Expires: 10 October 2026 Cisco
8 April 2026
Anonymous Bot Authentication: Authorization and Rate Limiting for Web
Agents
draft-rescorla-anonymous-webbotauth-00
Abstract
Automated agents ("bots") represent a large fraction of the traffic
to many Web sites. In some cases, this traffic is desired, in others
undesired, and in yet others, desired as long as it remains within
certain rate limits. This memo describes Anonymous Bot
Authentication (ABA), a system that allows Web site operators to
distinguish wanted from unwanted traffic, while not tying a given
request to a specific sender.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at
https://ekr.github.io/draft-rescorla-anonymous-webbotauth/draft-
rescorla-anonymous-webbotauth.html. Status information for this
document may be found at https://datatracker.ietf.org/doc/draft-
rescorla-anonymous-webbotauth/.
Source for this draft and an issue tracker can be found at
https://github.com/ekr/draft-rescorla-anonymous-webbotauth.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on 10 October 2026.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Architectural Overview . . . . . . . . . . . . . . . . . . . 4
2.1. Trade-offs . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Rate Limiting . . . . . . . . . . . . . . . . . . . . . . 6
3. Concrete Implementation With Privacy Pass and ARC . . . . . . 6
3.1. Providing Attestation to the Issuer . . . . . . . . . . . 8
3.2. Alternate Cryptographic Approaches . . . . . . . . . . . 9
3.2.1. Only Generic Zero-Knowledge Proofs . . . . . . . . . 9
3.2.2. Other Attestation Structures . . . . . . . . . . . . 9
4. Issuance Models . . . . . . . . . . . . . . . . . . . . . . . 10
4.1. Independent Attesters . . . . . . . . . . . . . . . . . . 10
4.2. Server as Attester . . . . . . . . . . . . . . . . . . . 10
4.3. Number of Attesters . . . . . . . . . . . . . . . . . . . 11
5. Relationship to Browser Authentication . . . . . . . . . . . 11
6. Use Case Analysis . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Site Use Cases . . . . . . . . . . . . . . . . . . . . . 11
6.1.1. Mitigating Volumetric Abuse by Bots . . . . . . . . . 11
6.1.2. Controlling Access by Bots . . . . . . . . . . . . . 12
6.1.3. Providing Different Content to Bots . . . . . . . . . 12
6.1.4. Auditing Bot Behavior . . . . . . . . . . . . . . . . 12
6.1.5. Classifying Traffic . . . . . . . . . . . . . . . . . 12
6.1.6. Authenticating Site Services . . . . . . . . . . . . 13
6.2. Bot Use Cases . . . . . . . . . . . . . . . . . . . . . . 13
6.2.1. IP Address Mobility . . . . . . . . . . . . . . . . . 13
6.2.2. Sharing IP Addresses . . . . . . . . . . . . . . . . 13
6.2.3. Robots.txt Alignment . . . . . . . . . . . . . . . . 13
6.2.4. Conveying Contextual Information . . . . . . . . . . 13
7. Conventions and Definitions . . . . . . . . . . . . . . . . . 13
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
8.1. Anonymity Set . . . . . . . . . . . . . . . . . . . . . . 14
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8.2. Credential Misuse . . . . . . . . . . . . . . . . . . . . 14
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1. Normative References . . . . . . . . . . . . . . . . . . 14
10.2. Informative References . . . . . . . . . . . . . . . . . 15
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
DISCLAIMER: This is a work-in-progress draft and has not yet seen
significant security analysis. It is being published at an early
stage for discussion purposes.
Automated agents ("bots") represent a large fraction of the traffic
to many Web sites. For example, Wikimedia reports that about 35% of
its traffic is from bots [PCMag-Wikipedia] and Cloudflare reports
that over 50% of traffic is automated [Cloudflare-2025]. High
traffic loads--even when from otherwise desired bots--can have
negative impacts on sites in terms of performance, stability, and
operational costs.
In addition, there may be certain types of bot traffic that sites
wish to heavily restrict or block entirely. For example:
* Volumetric traffic intended to create a DoS attack on the site.
* Non-volumetric traffic intended to attack the site.
* Scraping for specific purposes such as training AI agents.
[I-D.nottingham-webbotauth-use-cases] provides a more complete list
of potential use cases.
In response to this approach, there have been proposals to
authenticate automated clients. Sites can use behavioral analysis to
determine when traffic from a given endpoint appears bot-like (e.g.,
is high volume, has low latency between requests, appears to be
retrieving the entire site, etc.) and restrict access by those
endpoints unless they authenticate and the resulting identity is
acceptable to the site. [I-D.meunier-webbotauth-registry] describes
one such architecture, where identities are rooted in the DNS and
bots use digital signatures to tie their activity to a given
identity.
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While directly identifying each bot allows the site to precisely
monitor bots' behavior and restrict or block bots that it believes
are misbehaving, it also has potential negative effects on the open
Web, including:
* Allowing sites to precisely discriminate against specific bots,
even when those bots are acting in the public interest. For
example:
- Government sites might block bots which are tracking law
enforcement activity.
- Employment or housing sites might block bots which are
monitoring for discriminatory behavior.
- Shopping sites might block bots used for price comparison.
* Preventing users and groups from being able to anonymously
retrieve Web content using automated tools.
In many use cases, it is possible to resolve this tension using
anonymous credentials. When a bot presents an anonymous credential,
the Web site learns that the bot is part of some set of authorized
bots -- say those whose operators have agreed to good behavior -- and
not the specific identity of the bot or the bot operator.
This document describes an approach for using anonymous credentials
to authenticate bots to websites. In addition to laying out how the
system works, we describe the trade-offs between anonymity and fine-
grained abuse mitigation.
2. Architectural Overview
The overall structure of ABA is shown in Figure 1.
Alice Bob Attester Site
Register --------------------->
<----------- Attestation[Alice]
Register ------->
<---- Attestation[Bob]
Request + Attestation ---------------------------->
Site only knows Attester
not Alice or Bob
<------------------------------------------Response
Figure 1: Architectural Overview
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Prior to contacting the site, Alice and Bob both register with a
credential Attester, which is responsible for evaluating whether they
comply with the Attester's policies. They each are issued an
anonymous credential, which they can use to authenticate to the
server. What makes the credential anonymous is that the site only
learns that someone with a credential from the Attester is
authenticating, not whether it's Alice or Bob. This prevents the site
from discriminating _between_ customers of the same attester,
although it can discriminate between attesters.
As a result, while it is possible to distinguish authenticated from
unauthenticated bots, it is not possible to use the authentication
method to either (1) selectively block individual bots(2) determine
which bots are accessing which resources or (3) link multiple visits
by the same bot. It may still be possible to identify bots via other
mechanisms such as IP address or fingerprinting.
In some cases it may be sufficient merely to identify the attester,
for instance if the attester performs some vetting to ensure policy
compliance. However, in some cases this may be insufficient, as
discussed below.
2.1. Trade-offs
Assuring the anonymity of bot requests means imposes some limits on
how this authentication mechanism can be used to counter abuse.
These trade-offs are discussed in detail in Section 6, and the below
bullets provide a summary:
* ABA supports:
- Rate-limiting of requests by a a single bot
- Providing separate content to bots vs. humans
- Conditioning access based on a bot meeting certain criteria
- Conditioning access based on participation in some scheme or
protocol
- Classifying human vs. bot traffic
- IP address mobility and sharing of IP addresses
- Unlinkability between authenticated requests by the same client
* ABA does not support:
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- Allow lists / deny lists
- Auditing bot behavior
- Authenticating site services
Essentially, abuse controls that rely on knowing the identity of the
abusive party are incompatible with anonymous authentication.
2.2. Rate Limiting
In some cases it may be desirable to limit any individual agent to a
specific number of requests. For example, a given Attester may have
a large number of subscribers but only a few may access a given site.
In this case, overall rate limits for an attester will not be
effective, but individual rate limits are.
3. Concrete Implementation With Privacy Pass and ARC
This section describes how to implement ABA using Privacy Pass
[RFC9576], and Anonymous Rate-Limited Credentials
[I-D.ietf-privacypass-arc-protocol]
[I-D.ietf-privacypass-arc-crypto]. While this is not the only
possible implementation approach, it leverages existing deployed and
proposed IETF technologies and thus avoids duplicated functionality
and fits well into existing deployments.
We make use of the "Joint Origin and Issuer Deployment Model" from
Section 4.3 of [RFC9576], reproduced below in Figure 2:
+----------------------------.
+--------+ +----------+ | +--------+ +--------+ |
| Client | | Attester | | | Issuer | | Origin | |
+---+----+ +-----+----+ | +----+---+ +---+----+ |
| | `------|-------------|------'
|<-------------------------------- TokenChallenge --+
| | | |
|<=== Attestation ===>| | |
| | | |
+------------ TokenRequest ---------->| |
|<---------- TokenResponse -----------+ |
| |
+--------------------- Token ----------------------->
| |
Figure 2: Privacy Pass Model (Joint Origin and Issuer)
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In this model, the Client interacts with an Attester, which is
responsible for determining whether the client conforms to the
required policy. The Attester provides an Attestation which can then
be presented to the site (the Issuer in the diagram above), which
provides a Token. The bot can then use the Token to get services
from the site (the Origin in the diagram above). The Issuer and the
Origin are operated by the same entity (this is a technical
constraint of ARC).
ABA extends this scheme with a zero-knowledge proof (ZKP) system
(e.g., [I-D.google-cfrg-libzk]) in order to assure that the
Attester's attestation does not leak information to the Issuer that
could deanonymize the Client. This property is especially important
in the "server as attester" case Section 4.2, and is not assured by
ARC itself. In effect, ABA uses an expensive attestion and ZKP
operation to authorize the issuance of ARC tokens that can be used
cheaply on every request.
+----------------------------.
+--------+ +----------+ | +--------+ +--------+ |
| Client | | Attester | | | Issuer | | Origin | |
+---+----+ +-----+----+ | +----+---+ +---+----+ |
| | `------|-------------|------'
| | | |
+---- Cred-Request--->| | |
|<----Attestation------+ | |
| | | |
[Later]
|<-------------------------------- TokenChallenge --+
| | | |
+----TokenRequest + ZKP(Attestation)-->| |
|<--TokenResponse[ARC Credential]-----+ |
| |
+---------------- Request + ARC Credential -------->|
Figure 3: ABA with Privacy Pass
When a new Client is deployed, it first must register with some set
of Attesters. These Attesters will require the bot to demonstrate
that it complies with their policies, for instance that it is a
registered corporation, holds a domain name or an IP address block,
etc. Once the Attester is satisfied, it issues a Attestation to the
Client in the form of a CWT [RFC8392] signed by the Attester. This
Attestation can be used to authenticate to an arbitrary number of
Issuers.
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When a client contacts a new site for which it does not yet have an
ARC Credential, client uses the Attestation to authenticate to the
Issuer and request an ARC Credential. This authentication is
performed anonymously using a zero-knowledge proof that it has a
valid Attestation (shown as "ZKP(Attestation)" above), as described
in Section 3.1, so that the Issuer only learns the following
information:
1. This Client has been authenticated by the Attester.
2. This Client has not authenticated to the Issuer previously using
this Attestation (potentially within a given time window).
Assuming that the Client's proof verifies correctly and the Attester
is acceptable, the Issuer issues an ARC credential.
Each credential is associated with a rate limit, which may be
Attester-dependent. For instance, if the Attester has a policy
designed for high traffic bots, the Issuer might use one rate limit,
whereas if the policy is designed for low traffic bots, the Issuer
might use a lower rate limit. Note that the choice of rate limit is
entirely up to the Issuer, but because all Clients authenticated by a
given Attester are within the same anonymity set, it cannot use
different per-Client rate limits to multiple Clients attested to by
the same Attester. Similarly, because all clients whose credentials
are associated with the Issuer's key pair, all authorizations by
Clients using the
Once the Client has an ARC credential it can use it to authenticate
to the Origin repeatedly up to the number of authentications in the
rate limit associated with the Credential. These authentications are
unlinkable provided that the Client does not exceed the rate limit;
authentications beyond the rate limit are linkable. Because any
Credential can only be used once for a given Issuer within a given
time window, the total rate limit for a given Client/Issuer pair is
bounded by the limit associated with the ARC credential.
3.1. Providing Attestation to the Issuer
The protocol for Attestation to the Issuer is designed to meet the
following requirements:
* A Attestation can be used with an arbitrary number of Issuers.
* A Attestation can only be used once with a single Issuer within a
given time window
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* Attestation presentations are unlinkable, both between Issuer and
Attester and between Issuers.
These requirements can be met by using a signed credential (in this
case, a CWT [RFC8392]), along with a generic circuit-based zero-
knowledge proof system (in this case Longfellow-ZK
[I-D.google-cfrg-libzk]). The interaction between the Attester and
the Client just yields an ordinary CWT and then the Client proves in
zero-knowledge that they have a valid Attestation from a given
Attester.
In order to prevent replay, the proof also includes an Issuer-
specific nullifier tied to the Issuer's domain name and the current
time window. While the proof itself varies between presentations,
the nullifier remains the same and therefore can be used to detect
replay.
Because we are using a generic ZK system it should also be possible
to use it to conceal the Attester if desired: for example if there
are multiple Attesters who follow equivalent vetting procedures, then
the Issuer does not need to know which Attester the Client used; the
ZKP can be designed to prove that the Client has a Attestation from
one of a set of Attesters within the same equivalence class; of
course, the Issuer will need to use the same rate limit for all such
Attesters.
3.2. Alternate Cryptographic Approaches
This section considers a number of alternate cryptographic approaches
and explains the choice of primitives in this section.
3.2.1. Only Generic Zero-Knowledge Proofs
In principle, it is possible to omit the use of ARC and instead have
the Client authenticate each transaction directly to the Origin.
However, even efficient generic ZKP systems like Longfellow-ZK have
far higher computational and bandwidth costs than more limited
systems such as the one used in ARC. Using a generic ZKP system to
demonstrate ownership of an attested Attestation to the Issuer and
then using that single interaction to obtain an ARC credential makes
it possible to amortize the generic proof over a large number of
subsequent interactions.
3.2.2. Other Attestation Structures
There are a number of other potential ways to convey attestations to
the Issuer, but each fails to fulfill one of the requirements in
Section 3.1.
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* _Non-anonymous credentials_ allow for linkage of bots at
redemption time.
* _Single-show credentials_ like those in Privacy Pass either allow
or require the bot to interact with the Attester for each site it
wants to interact with (otherwise linkage is possible).
* _Camenisch-Lysanskaya credentials_ do not prevent multiple shows
to the same server, thus precluding rate limiting.
* _BBS+_ credentials require the use of pairings and have no obvious
transition to post-quantum algorithms.
Note that in cases where the Attester and the Issuer are one and the
same (see Section 4.2), it is not necessary to convey the attestation
to the Issuer and so the generic ZKP system can be omitted.
4. Issuance Models
Anonymous credentials are compatible with a variety of issuance
models, as discussed in this section.
4.1. Independent Attesters
Much like millions of websites rely on a much smaller number of
independent WebPKI certificate authorities, it is possible to have a
system of independent Attesters that are broadly relied upon by many
websites. Each attester could publish the policy that it uses to
issue credentials (e.g., verifying corporate existence, subject pays
$100, etc.). Sites can then select which attesters have policies
they are willing to accept. It is also possible to have multiple
Attesters who conform to a common set of policies, as in the WebPKI,
where each CA has to meet the same requirements, but site operators
have the choice of which CA to use.
4.2. Server as Attester
It is also possible for a server to act as their own Attester. This
is not likely to be practical for small sites, as bots will simply
opt not to authenticate to those sites at all. However, a large CDN
which hosts many sites might opt to operate its own Attester, and it
could be practical for bots to register with such an Attester. Note
that this approach makes it possible for the Attester to refuse
service to individual Clients, but not to selectively do so for
individual customers unless it uses separate Issuers for each of
those customers.
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The ZKP element of ABA ensures that clients remain anonymous even in
this case, since the client's redemption of an Attestation is not
linkable to its issuance.
4.3. Number of Attesters
In general, it is desirable for bots to be able to acquire a
relatively small number of credentials and have high confidence that
those credentials will be compatible with most if not all of the
sites that the bot wishes to contact. This can be most
straightforwardly accomplished if there is only a small number of
attesters, but it can also work if there are a larger number of
attesters but sites converge on a relatively small number of policies
(expressed as which attesters they support) such that a bot can
acquire a set of credentials that covers all of those policies. The
least desirable outcome is if bots routinely are prompted to provide
credentials for a new attester.
5. Relationship to Browser Authentication
There is significant overlap with existing work on anonymous
authentication happening in the PrivacyPass WG and in the W3C
AntiFraud Community Group. While that work is directed towards
access control for users, the same cryptographic techniques can be
used to authenticate bots. A good description of the vision and
requirements can be found at [PACT-Issue]. The ideal scenario would
be to be able to use compatible tokens for users and bots, differing
only in the issuance policies, the attesters, and the rate limits.
6. Use Case Analysis
[I-D.nottingham-webbotauth-use-cases] describes a set of use cases
for web bot authentication. The architecture described in this
document address some but not all of these use cases. This is
intentional rather than a deficiency; the objective is to address use
cases which are compatible with limiting the negative impact of bots
while avoiding making it trivial for sites to discriminate against
individual bots. The remainder of this section addresses each use
case individually.
6.1. Site Use Cases
6.1.1. Mitigating Volumetric Abuse by Bots
This document directly addresses the topic of volumetric abuse,
because bots can be authenticated and authenticated bots can be
restricted to specific bandwidth limits. Once a bot has exceeded its
limit, it can be blocked.
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6.1.2. Controlling Access by Bots
[I-D.nottingham-webbotauth-use-cases] provides the following example
applications of controlling access:
- Only allow access by bots on an allow list;
- Disallow access to bots on an explicit deny list;
- Condition access upon meeting some criteria (e.g., non-profit,
certification by a third party);
- Condition access upon participation in some scheme or protocol
(e.g., payment for access);
Note that the first two imply some notion of bots being tied to a
real-world identity, whereas the remaining do not necessarily
require it.
ABA can be used for the second two use cases and can be used for some
versions of the first two use cases. However, the more fine-grained
controls are used (e.g., by having many Attesters with different
policies) the worse the privacy and scalability properties of the
system become.n
6.1.3. Providing Different Content to Bots
The architecture in this document may be usable to provide different
content to bots generally than humans depending on the structure of
attesters (e.g., does a given attester issue to both bots and to
humans) and whether techniques are used to conceal which attester is
in use. However, they are not generally useful to provide different
content to specific bots.
6.1.4. Auditing Bot Behavior
This use case is not addressed by this document.
6.1.5. Classifying Traffic
Because this use case does not depend on determining which bot is
which, but only which traffic is human versus bot, the architecture
in this document may be able to address this use case, depending on
the ultimate deployment model.
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6.1.6. Authenticating Site Services
This use case is not addressed by this document.
6.2. Bot Use Cases
6.2.1. IP Address Mobility
ABA provides authentication for bots independent of IP address.
Because ABA authentication is at the Attester rather than the Client
level, it is not possible to use ABA to build bot-specific
reputations based on observed bot activity; instead the Attester is
responsible for assessing bots and then providing that information to
sites.
6.2.2. Sharing IP Addresses
Because ABA provides authentication independent of IP address, it
allows sites to discriminate between unauthenticated users of an IP
address and those which are ABA-authenticated, thus reducing the
negative reputational side effects of misuse by unauthenticated users
sharing the same IP address.
6.2.3. Robots.txt Alignment
This use case is not addressed by this document.
6.2.4. Conveying Contextual Information
Because different Attesters can have different policies and Attesters
can have multiple policies, ABA allows for limited conveyance of
contextual information. While in principle this information can be
arbitrarily fine-grained, coarse-grained information ensures a larger
anonymity set (see Section 4.3).
7. Conventions and Definitions
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.
8. Security Considerations
The precise security and privacy details of a system of this type
depend on the detailed cryptographic mechanism being deployed.
However, it is possible to make some general observations.
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8.1. Anonymity Set
The anonymity set for a given transaction is the set of credentials
associated with a given Attester, or, if Attester hiding is used, the
set of credentials associated with the set of attesters. However, it
is still possible to learn information about the client by
manipulating the Attester set. For example, a site acting as an
Attester could use different keys for each user or a site could use
different Attester subsets to identify which of a set of Attesters
was in use. Transparency/consistency mechanisms like
[I-D.ietf-privacypass-key-consistency] may be useful in detecting
this form of attack.
8.2. Credential Misuse
Because clients are anonymous, some forms of misuse are harder to
manage. For example:
* Two clients can collude to exceed rate limits if they are
interacting with disjoint sites.
* If registration standards are low and registration is cheap a bot
can obtain multiple credentials.
* Patterns of misuse (e.g., credential stuffing) become harder to
detect.
Note that existing mechanisms, such as IP address, will continue to
be usable, but the techniques described in this document may not add
to the server's ability to address these issues.
9. IANA Considerations
This document has no IANA actions.
10. References
10.1. Normative References
[I-D.google-cfrg-libzk]
Frigo, M. and A. shelat, "The Longfellow Zero-knowledge
Scheme", Work in Progress, Internet-Draft, draft-google-
cfrg-libzk-01, 2 September 2025,
<https://datatracker.ietf.org/doc/html/draft-google-cfrg-
libzk-01>.
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[I-D.ietf-privacypass-arc-crypto]
Yun, C., Wood, C. A., and A. F. Faz-Hernandez, "Anonymous
Rate-Limited Credentials Cryptography", Work in Progress,
Internet-Draft, draft-ietf-privacypass-arc-crypto-01, 2
March 2026, <https://datatracker.ietf.org/doc/html/draft-
ietf-privacypass-arc-crypto-01>.
[I-D.ietf-privacypass-arc-protocol]
Yun, C., Wood, C. A., and A. F. Faz-Hernandez, "Privacy
Pass Issuance Protocol for Anonymous Rate-Limited
Credentials", Work in Progress, Internet-Draft, draft-
ietf-privacypass-arc-protocol-01, 2 March 2026,
<https://datatracker.ietf.org/doc/html/draft-ietf-
privacypass-arc-protocol-01>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/rfc/rfc8392>.
[RFC9576] Davidson, A., Iyengar, J., and C. A. Wood, "The Privacy
Pass Architecture", RFC 9576, DOI 10.17487/RFC9576, June
2024, <https://www.rfc-editor.org/rfc/rfc9576>.
10.2. Informative References
[Cloudflare-2025]
Cloudflare, "Cloudflare 2025 Year in Review", 2025,
<https://radar.cloudflare.com/year-in-review/2025>.
[I-D.ietf-privacypass-key-consistency]
Davidson, A., Finkel, M., Thomson, M., and C. A. Wood,
"Key Consistency and Discovery", Work in Progress,
Internet-Draft, draft-ietf-privacypass-key-consistency-01,
10 July 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-privacypass-key-consistency-01>.
[I-D.meunier-webbotauth-registry]
Guerreiro, M., Kirazci, U., and T. Meunier, "Registry and
Signature Agent card for Web bot auth", Work in Progress,
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Internet-Draft, draft-meunier-webbotauth-registry-01, 20
October 2025, <https://datatracker.ietf.org/doc/html/
draft-meunier-webbotauth-registry-01>.
[I-D.nottingham-webbotauth-use-cases]
Nottingham, M., "Use Cases for Authentication of Web
Bots", Work in Progress, Internet-Draft, draft-nottingham-
webbotauth-use-cases-02, 1 April 2026,
<https://datatracker.ietf.org/doc/html/draft-nottingham-
webbotauth-use-cases-02>.
[PACT-Issue]
Jackson, D., "Private Access Control Tokens", 2 December
2025,
<https://github.com/antifraudcg/proposals/issues/22>.
[PCMag-Wikipedia]
Kan, L., "Wikipedia Faces Flood of AI Bots That Are
'Eating Bandwidth,' Raising Costs", 14 February 2024,
<https://www.pcmag.com/news/wikipedia-faces-flood-of-ai-
bots-that-are-eating-bandwidth-raising-costs>.
Acknowledgments
TODO acknowledge.
Authors' Addresses
Eric Rescorla
Independent
Email: ekr@rtfm.com
Richard L. Barnes
Cisco
Email: rlb@ipv.sx
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