[SSL, ZT] PQC Zero Trust overview (#20798)

* Small edits to existing text

* Add new section under pqc index.mdx

* Create new page outlining ZT solutions available

* Adjust pcx_content_type

* Add digrams for both use cases

* Fix broken link

* Suggestion: replacement of clientless access terminology

* Adjust text following PM review

* Further review and link to new page from pqc-to-origin

* Apply suggestions from code review

Co-authored-by: Max Phillips <[email protected]>

* Improve cross-linking following pcx review

---------

Co-authored-by: Max Phillips <[email protected]>

Author: RebeccaTamachiro

src/assets/images/ssl/pqc-clientless-access.png

@@ -97,6 +97,8 @@ You can still apply all [network policy filters](/cloudflare-one/policies/gatewa
 
 Gateway supports post-quantum cryptography using a hybrid key exchange with X25519 and MLKEM768 over TLS 1.3. Once the key exchange is complete, Gateway uses AES-128-GCM to encrypt traffic.
 
+Refer to [Post-quantum cryptography](/ssl/post-quantum-cryptography/) to learn more.
+
 ## FIPS compliance
 
 By default, TLS decryption can use both TLS version 1.2 and 1.3. However, some environments such as FedRAMP may require cipher suites and TLS versions compliant with FIPS 140-2. FIPS compliance currently requires TLS version 1.2.

src/assets/images/ssl/pqc-secure-web-gateway.png

@@ -12,7 +12,7 @@ description: Get an overview of how Cloudflare is deploying post-quantum cryptog
 
 Post-quantum cryptography (PQC) refers to cryptographic algorithms that have been designed to resist attacks from [quantum computers](https://www.cloudflare.com/learning/ssl/quantum/what-is-quantum-computing/). Cloudflare has been researching and [writing about post-quantum](https://blog.cloudflare.com/tag/post-quantum/) since 2017.
 
-To protect you against the risk of [harvest now, decrypt later](https://en.wikipedia.org/wiki/Harvest_now,_decrypt_later), and considering all the [connections](#three-connections-in-the-life-of-a-request) that take place when your website or application is on Cloudflare, we have deployed and are actively expanding the use of [post-quantum hybrid key agreement](#hybrid-key-agreement).
+To protect you against the risk of [harvest now, decrypt later attacks](https://en.wikipedia.org/wiki/Harvest_now,_decrypt_later), and considering all the [connections](#three-connections-in-the-life-of-a-request) that take place when your website or application is on Cloudflare, we have deployed and are actively expanding the use of [post-quantum hybrid key agreement](#hybrid-key-agreement).
 
 Refer to [Cloudflare Radar](https://radar.cloudflare.com/adoption-and-usage#post-quantum-encryption-adoption) for current statistics on the adoption of PQ encryption in requests to Cloudflare, and visit [pq.cloudflareresearch.com](https://pq.cloudflareresearch.com) to check if your connection is secured using PQ key agreement.
 
@@ -32,7 +32,7 @@ As explained in our [blog post](https://blog.cloudflare.com/pq-2024/#two-migrati
 
 ### Hybrid key agreement
 
-With TLS 1.3, [X25519](https://en.wikipedia.org/wiki/Curve25519) - an Elliptic Curve Diffie-Hellman (ECDH) protocol - is the most commonly used algorithm in key agreement. However, its security can be easily broken by quantum computers using [Shor's algorithm](https://en.wikipedia.org/wiki/Shor%27s_algorithm).
+With TLS 1.3, [X25519](https://en.wikipedia.org/wiki/Curve25519) - an Elliptic Curve Diffie-Hellman (ECDH) protocol - is the most commonly used algorithm in key agreement. However, its security can be broken by quantum computers using [Shor's algorithm](https://en.wikipedia.org/wiki/Shor%27s_algorithm).
 
 It is urgent to migrate key agreement to post-quantum algorithms as soon as possible. The objective is to protect against an adversary capable of harvesting today's encrypted communications and storing it until some time in the future when they can gain access to a sufficiently powerful quantum computer to decrypt it.
 
@@ -83,6 +83,10 @@ As announced in [September 2023](https://blog.cloudflare.com/post-quantum-crypto
 
 ### 3. Cloudflare to your origin
 
-Finally, Cloudflare also supports [hybrid key agreements](#hybrid-key-agreement) when connecting to origins. In this case, post-quantum secured connections will depend on the origin servers also supporting PQC.
+Finally, Cloudflare also supports [hybrid key agreements](#hybrid-key-agreement) when connecting to origins. In this case, post-quantum secured connections will depend on the origin servers also supporting PQC. Customers can also configure connections to origin servers via [PQ Cloudflare Tunnel](/ssl/post-quantum-cryptography/pqc-and-zero-trust/).
 
-Refer to [Post-quantum cryptography between Cloudflare and origin servers](/ssl/post-quantum-cryptography/pqc-to-origin/) for details.
+Refer to [Post-quantum cryptography between Cloudflare and origin servers](/ssl/post-quantum-cryptography/pqc-to-origin/) for details.
+
+## Protect corporate network traffic
+
+With [Zero Trust](/cloudflare-one/), Cloudflare allows organizations to upgrade their sensitive network traffic to PQC without the hassle of individually upgrading each and every corporate application, system, or network connection. Refer to [Post-quantum cryptography in Cloudflare's Zero Trust platform](/ssl/post-quantum-cryptography/pqc-and-zero-trust/) for details.

src/content/docs/cloudflare-one/policies/gateway/http-policies/tls-decryption.mdx

@@ -0,0 +1,56 @@
+---
+pcx_content_type: reference
+title: Post-quantum cryptography in Cloudflare's Zero Trust platform
+sidebar:
+  order: 4
+  label: PQC and Zero Trust
+---
+
+The [Cloudflare Zero Trust platform](/cloudflare-one/) replaces legacy corporate security perimeters with Cloudflare's global network, making access to the Internet and to corporate resources faster and safer for teams around the world.
+
+Refer to the sections below to learn about the use cases supported by the Zero Trust platform in this [first phase of quantum readiness](/ssl/post-quantum-cryptography/).
+
+## Agentless Cloudflare Access
+
+You can use [Cloudflare Access](/cloudflare-one/policies/access/) [self-hosted applications](/cloudflare-one/applications/configure-apps/self-hosted-public-app/) in an agentless configuration to protect your organization's Internet traffic to internal web applications. Refer to the [learning path](/learning-paths/zero-trust-web-access/initial-setup/) for detailed guidance.
+
+Even if the applications themselves have not yet migrated to post-quantum (PQ) cryptography, they will be protected against quantum threats.
+
+![Diagram of how post-quantum cryptography works in clientless connections to Access applications](~/assets/images/ssl/pqc-clientless-access.png).
+
+Here is how it works today:
+
+**1. PQ connection via browser**
+
+As long as the end-user uses a modern web browser that supports post-quantum key agreement (for example, Chrome, Edge, or Firefox), the connection from the device to Cloudflare's network is secured via TLS 1.3 with post-quantum key agreement.
+
+**2. PQ within Cloudflare's global network**
+
+If the user and origin server are geographically distant, then the user's traffic will enter Cloudflare's global network in one geographic location (such as Frankfurt), and exit at another (such as San Francisco). As this traffic moves from one data center to another inside Cloudflare's global network, these hops through the network are secured via TLS 1.3 with post-quantum key agreement.
+
+**3. PQ Cloudflare Tunnel**
+
+Customers establish a [Cloudflare Tunnel](/cloudflare-one/connections/connect-networks/) from their data center or public cloud — where their corporate web application is hosted — to Cloudflare's network. This tunnel is secured using TLS 1.3 with post-quantum key agreement, safeguarding it from [harvest now, decrypt later attacks](https://en.wikipedia.org/wiki/Harvest_now,_decrypt_later).
+
+Putting it together, Cloudflare Access can provide end-to-end quantum safety for accessing corporate HTTPS applications, without requiring customers to upgrade the security of corporate web applications.
+
+## Secure Web Gateway
+
+A [secure web gateway (SWG)](https://www.cloudflare.com/learning/access-management/what-is-a-secure-web-gateway/) is used to secure access to third-party websites on the public Internet by intercepting and inspecting TLS traffic.
+
+[Cloudflare Gateway](/cloudflare-one/policies/gateway/http-policies/) is now a [quantum-safe SWG for HTTPS traffic](/cloudflare-one/policies/gateway/http-policies/tls-decryption/#post-quantum-support). As long as the third-party website that is being inspected supports post-quantum key agreement, then Cloudflare's SWG also supports post-quantum key agreement. This is true regardless of the on-ramp that you use to get to Cloudflare's network, and only requires the use of a browser that supports post-quantum key agreement.
+
+![Diagram of how post-quantum cryptography works with Cloudflare's Secure Web Gateway](~/assets/images/ssl/pqc-secure-web-gateway.png).
+
+Cloudflare Gateway's HTTPS filtering feature involves two post-quantum TLS connections, as follows:
+
+**1. PQ connection via browsers**
+
+A TLS connection is initiated from the user's browser to a data center in Cloudflare's network that performs the TLS inspection. As long as the end-user uses a modern web browser that supports post-quantum key agreement (for example, Chrome, Edge, or Firefox), this connection is secured by TLS 1.3 with post-quantum key agreement.
+
+**2. PQ connection to the origin server**
+
+A TLS connection is initiated from a data center in Cloudflare's network to the origin server, which is typically controlled by a third party. The connection from Cloudflare's SWG currently supports post-quantum key agreement, as long as the third-party's origin server also already supports post-quantum key agreement. You can test this out by using https://pq.cloudflareresearch.com/ as your third-party origin server.
+
+Putting it together, Cloudflare Gateway is quantum-ready to support secure access to any third-party website that is quantum ready today or in the future.
+

src/content/docs/ssl/post-quantum-cryptography/index.mdx

@@ -16,6 +16,8 @@ With X25519, the [ClientHello](https://www.cloudflare.com/learning/ssl/what-happ
 
 This poses a question of how the origin servers - as well as other middleboxes (routers, load balancers, etc) - will handle this change in behavior. Although allowed by the TLS 1.3 standard ([RFC 8446](https://www.rfc-editor.org/rfc/rfc8446.html)), a split ClientHello risks not being handled well due to [protocol ossification](https://en.wikipedia.org/wiki/Protocol_ossification) and implementation bugs. Refer to our [blog post](https://blog.cloudflare.com/post-quantum-to-origins/) for details.
 
+Customers can also configure connections to origin servers via [PQ Cloudflare Tunnel](/ssl/post-quantum-cryptography/pqc-and-zero-trust/).
+
 ## ClientHello from Cloudflare
 
 To reduce the risk of any issues when connecting to servers that are not ready for hybrid key agreements, Cloudflare leverages HelloRetryRequest. This means that, instead of sending [X25519MLKEM768](/ssl/post-quantum-cryptography/#hybrid-key-agreement) immediately as a keyshare [^1], Cloudflare will by default only advertise support for it.