New iPhone App Uses Cryptographic Hashing to Verify Photo Authenticity

A new iPhone app called Veridenz allows users to create a cryptographic witness for photos without uploading the original image. The app hashes the file, signs the hash using a dedicated identity stored in Apple Keychain, and publishes the witness to Nostr relays while keeping the photo secure within the app. This method verifies if a photo file matches the original witnessed, rather than confirming the authenticity of the scene itself. The developer emphasizes that the app does not collect any data and is designed for scenarios where stronger documentation could be useful later, such as contractors documenting completed work or homeowners capturing insurance damage. Comments discuss the technical aspects, including whether the hash is based on the actual file or perceptual hashing of the image scene. Critics argue that the method is fragile due to potential alterations during file compression or metadata stripping, while others highlight niche use cases where this verification could be valuable. The app’s tagline, ‘Capture. Prove. Verify,’ underscores its purpose in providing cryptographic proof of photo authenticity without compromising privacy.