In short
- A SHA-256 hash is a 64-character fingerprint of a file's exact bytes; change one byte and the fingerprint changes completely.
- Vesta hashes every finished render and every export and records the fingerprint in an append-only ledger that cannot be edited or deleted.
- Anyone can check a file against the ledger on Vesta's compliance page; the file is fingerprinted in the browser and never uploaded.
- Listing sites usually recompress photos, so a copy downloaded from a portal will not match. Keep the file exactly as you exported it.
- The record is not required by AB 723. It is evidence, for the day a buyer or a board asks what you actually published.
AB 723 asks for a disclosure on every altered listing photo and a link to the original. It does not ask anyone to keep records. But disputes over listing photos tend to arrive months later, after the listing has changed, the portal has recompressed the images and nobody remembers which version went where. When that happens, the useful question is simple: can you show exactly what you published?
What a hash is
A cryptographic hash turns a file of any size into a short, fixed-length fingerprint. SHA-256, the one Vesta uses, produces 64 hexadecimal characters. Two properties make it useful as evidence.
- It is exact. The same bytes always give the same fingerprint, and changing a single byte gives a completely different one. There is no "close".
- It only works one way. You cannot work backwards from a fingerprint to the image, and you cannot practically construct a different image with the same fingerprint.
So if you hold a file whose fingerprint matches one recorded on a certain date, you hold that exact file — not a similar one, not a re-save of it.
What Vesta records
When a render finishes, Vesta applies the disclosure mark, fingerprints the finished file and writes a ledger entry: the fingerprint, the version of the disclosure it carries, and when. When you export, the delivered file is fingerprinted and recorded again, because an export may be resized or re-encoded and would otherwise not match.
The ledger is append-only at the database level. A trigger rejects any attempt to update or delete an entry once it is written, so the record cannot be quietly corrected after the fact — by a customer, by a support request, or by us.
How to check a file
The compliance page has a public lookup. Choose an image and your browser fingerprints it locally; only the 64-character fingerprint is sent. If Vesta produced that exact file, the lookup says so, with the disclosure version and the date it was recorded. It reveals nothing about who produced it.
Where it breaks: recompression
Most MLS systems and listing portals recompress photos when they are uploaded, to save space and bandwidth. Recompression changes the bytes, which changes the fingerprint. A copy downloaded from a portal will almost never match the file you exported, even though it looks identical.
That is a property of exact fingerprints, not a failure of the record. It does mean the evidence is only as good as your own copy:
- Keep every exported file exactly as it came out of Vesta. Do not re-save it, rename-and-resize it or run it through another editor.
- Store it with the listing's other records, alongside your original captures.
- When you need to prove what you published, check your kept copy — not the version on the portal.