Oblivious HTTP (OHTTP)
What is Oblivious HTTP (OHTTP)?
Oblivious HTTP (OHTTP)An IETF-standardized HTTP-over-HPKE relay protocol (RFC 9458) that decouples client identity from request content by splitting trust between a relay (sees IP, not content) and a gateway (sees content, not IP).
Oblivious HTTP (OHTTP), specified in RFC 9458 (2024), is a privacy-preserving relay protocol for HTTP requests. The client encrypts the inner request with HPKE (Hybrid Public-Key Encryption, RFC 9180) using the gateway server's public key, then sends the encrypted payload over a normal TLS connection to a separate relay server. The relay decrypts only the outer envelope, sees the client's IP but not the request, and forwards the encrypted payload to the gateway; the gateway decrypts and processes the request, sees the request and response, but never sees the client's IP. This split-trust model means no single party knows both 'who' and 'what'. Use cases include Apple Private Relay-style web access, DNS over Oblivious HTTP, telemetry pipelines (Mozilla, Cloudflare), 'private prefetch proxy' deployments, and certificate-revocation lookups. The companion 'oblivious DoH' (ODoH, RFC 9230) is an OHTTP-style relay specific to DNS resolution. OHTTP requires the client to trust that the relay and gateway are run by non-colluding parties, which is the central operational assumption.
● Examples
- 01
An operating system fetches certificate-revocation status via OHTTP so that revocation lookups cannot be tied to user IPs by either the CA or the network operator alone.
- 02
A telemetry pipeline ships product-usage events through OHTTP, routing through a Fastly relay to a vendor's gateway, ensuring the vendor cannot tie events to client IPs.
● Frequently asked questions
What is Oblivious HTTP (OHTTP)?
An IETF-standardized HTTP-over-HPKE relay protocol (RFC 9458) that decouples client identity from request content by splitting trust between a relay (sees IP, not content) and a gateway (sees content, not IP). It belongs to the Network Security category of cybersecurity.
What does Oblivious HTTP (OHTTP) mean?
An IETF-standardized HTTP-over-HPKE relay protocol (RFC 9458) that decouples client identity from request content by splitting trust between a relay (sees IP, not content) and a gateway (sees content, not IP).
How does Oblivious HTTP (OHTTP) work?
Oblivious HTTP (OHTTP), specified in RFC 9458 (2024), is a privacy-preserving relay protocol for HTTP requests. The client encrypts the inner request with HPKE (Hybrid Public-Key Encryption, RFC 9180) using the gateway server's public key, then sends the encrypted payload over a normal TLS connection to a separate relay server. The relay decrypts only the outer envelope, sees the client's IP but not the request, and forwards the encrypted payload to the gateway; the gateway decrypts and processes the request, sees the request and response, but never sees the client's IP. This split-trust model means no single party knows both 'who' and 'what'. Use cases include Apple Private Relay-style web access, DNS over Oblivious HTTP, telemetry pipelines (Mozilla, Cloudflare), 'private prefetch proxy' deployments, and certificate-revocation lookups. The companion 'oblivious DoH' (ODoH, RFC 9230) is an OHTTP-style relay specific to DNS resolution. OHTTP requires the client to trust that the relay and gateway are run by non-colluding parties, which is the central operational assumption.
How do you defend against Oblivious HTTP (OHTTP)?
Defences for Oblivious HTTP (OHTTP) typically combine technical controls and operational practices, as detailed in the full definition above.
What are other names for Oblivious HTTP (OHTTP)?
Common alternative names include: OHTTP, RFC 9458.
● Related terms
- network-security№ 374
DNS over HTTPS (DoH)
A protocol that encrypts DNS queries by transporting them inside HTTPS, preventing on-path observers from reading or modifying lookups.
- network-security№ 376
DNS over TLS (DoT)
A protocol that encrypts DNS queries inside a dedicated TLS session, protecting them from eavesdropping and tampering on the wire.
- network-security№ 375
DNS over QUIC (DoQ)
A DNS transport (RFC 9250, 2022) that runs DNS queries over QUIC, providing the confidentiality and integrity of DoT/DoH with lower handshake latency, better connection migration, and head-of-line blocking immunity from QUIC.
- network-security№ 557
HTTPS
HTTP carried over a TLS-protected connection, providing confidentiality, integrity, and server authentication for web traffic.
- privacy№ 960
Privacy Sandbox
Google's umbrella initiative for replacing third-party cookies and cross-site identifiers with privacy-preserving alternatives — Topics, Protected Audience (FLEDGE), Attribution Reporting, and on-device APIs — under heavy regulatory and competitor scrutiny.
- network-security№ 1279
TLS (Transport Layer Security)
The IETF-standardized cryptographic protocol that provides confidentiality, integrity, and authentication for traffic between two networked applications.