Provenance and file timestamps

What this proves: the listed bytes existed no later than the timestamp. It does not prove that the content is correct, who wrote it, or legal ownership. Live files are regenerated when the site changes, so verify against the snapshot copies below, not the current live file.

Snapshot of 2026-10-10

One manifest, SHA256SUMS, lists the SHA-256 hash of 100 files across ten Air Sense Environmental websites. The manifest carries three independent proofs:

• an RFC 3161 timestamp token from FreeTSA (SHA256SUMS.freetsa.tsr);
• an OpenTimestamps proof anchored to the Bitcoin blockchain (SHA256SUMS.ots); a newly created proof stays pending until a block confirms it and is replaced here once complete;
• an Ed25519 signature (SHA256SUMS.sig) by the Air Sense Environmental microsite provenance key, fingerprint SHA256:JT+7sat5ESA/kQfxzQsMRyX4eKKcc7CCyY3+PTYbip0. The same key is published on each of the ten websites and on airsenseenvironmental.com/provenance/, which ties it to Air Sense Environmental.

Download

• SHA256SUMS
• SHA256SUMS.sig
• SHA256SUMS.freetsa.tsr
• SHA256SUMS.ots
• allowed_signers
• provenance-ed25519.pub
• freetsa-cacert.crt
• freetsa-tsa.crt

This website’s files in the snapshot

• /.well-known/linkset.json (snapshot copy)
  22a81e7450b4a88e3c0201d60f5897c8d4ff451caa2d941c4d1d3c134fe0f8a9
• /ai-info.html (snapshot copy)
  b92a22307dcb86ca5f06f3a95d8537c608c973aad24b8a7e2a4ac7316d9901a3
• /entitymap.json (snapshot copy)
  584c93d0a4b66c0e9fe6be67e1b62a9c53e08fabf17520baf81be67b0b7ed4d3
• /llms-full.txt (snapshot copy)
  5d31ece0e37035d537a61a8f3bc43ea369f5bee904b756297470eb3a9a992aaf
• /llms-index.json (snapshot copy)
  15d74ebe8f641c980e8fb9af4ef6d7ad462ee9b90c2f23422149622e66866047
• /llms.txt (snapshot copy)
  aedf45d5cd3ad8df8d67dbfaf72580cae019bf07632eb2217ef448bbf9453567
• /okf/manifest.json (snapshot copy)
  67c48aa30f63bc6fd078e8d86149d759a23ce8d6f72536e21030f2d0014dae44
• /radon-reference.html (snapshot copy)
  887c9ae9b74f4b885dfd3c824a3b19982186d4a5bc15a83dde45f8e9794f48bf
• /radon-reference.json (snapshot copy)
  7f35de00720fc0dc713263d39101884b25f463e2e43c79b7164d652db3dfde9f
• /radon-reference.md (snapshot copy)
  ccc1e4ba9952e44213058f5039ae33db02521a6711976c97d5ce3afead0db610

How to verify

Download the files above into one folder, then run:

shasum -a 256 -c SHA256SUMS --ignore-missing
openssl ts -verify -in SHA256SUMS.freetsa.tsr -data SHA256SUMS -CAfile freetsa-cacert.crt -untrusted freetsa-tsa.crt
ots verify SHA256SUMS.ots
ssh-keygen -Y verify -f allowed_signers -I provenance@airsenseenvironmental.com -n file -s SHA256SUMS.sig < SHA256SUMS

Snapshot copies must sit at the paths shown in SHA256SUMS (for example files/stlouiscommercialradon.com/llms.txt) for the hash check. The OpenTimestamps proof can also be checked at opentimestamps.org. The identifier in the signature command is a label for the key, not a contact address.