Signed links¶

A signed link is a time-limited address for an image or a rendition of it that a system can hand out without a Picsha account, for example a customer-facing app that shows photos from your library without making them public.

Inside Picsha¶

You do not need to sign anything to use Picsha DAM or Picsha Lab. Every image the apps show, download or send to a printer is fetched through a link that Picsha signs for you behind the scenes, so a copied address stops working and nothing in your library is reachable without signing in. Public image links are the one deliberately open kind of link.

For your own systems¶

Systems that integrate with the Picsha AI API directly can mint signed links themselves with their API key, with no call to Picsha for each link. The scheme, with test vectors, is published in the Picsha AI developer documentation: picsha.ai/docs/signed-urls. In short, the link's path and query are canonicalized, signed with HMAC-SHA256 under the API key, and the first sixteen hex characters are appended as sig; an optional exp (Unix seconds) inside the signed query makes the link expire. A changed parameter, a wrong signature or a passed expiry answers 403.

Your organization's API key is held by Picsha and your administrators; ask Picsha support to set up API access for an integration.