content addressing is a way of looking up pages or files by hashes of their contents rather than the URL of their origin server.
Use in existing web standards
Content-Security-Policy: default-src 'self'; script-src 'self' https://example.com 'sha256-base64 encoded hash'
Sub-resource Integrity does too
Conformant user agents must support the SHA-256, SHA-384 and SHA-512 cryptographic hash functions for use as part of a request’s integrity metadata and may support additional hash functions. User agents should refuse to support known-weak hashing functions like MD5 or SHA-1 and should restrict supported hashing functions to those known to be collision-resistant.
Request.integrity Read only Contains the subresource integrity value of the request (e.g., sha256- BpfBw7ivV8q2jLiT13fxDYAe2tJllusRSZ273h2nFSE=).
Proposed new standards
Some discussion at IETF - see this presentation and drafts:
Note the use of this header:
Strange de facto standards
HTTP Extensions for a Content-Addressable Web (2001) no longer on the web except as a mailing list archive
If servers use a prefixed hash in the above format as an ETag, that could enable incremental usage of content hashes.