A new iPhone app called Veridenz allows users to create cryptographic witnesses for photos without uploading the original images. The app hashes photos, signs them with a secure identity stored in Apple Keychain, and publishes these witnesses to Nostr relays. Veridenz aims to verify if a photo file matches the one that was initially witnessed, rather than attempting to authenticate the scene's genuineness. Users do not require a Nostr account as the app manages its own signing identity, and the developer states no data from the app is collected.