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 tool addresses the need to verify whether a photo file matches the original witnessed, rather than confirming the authenticity of the scene itself. Users don't need a Nostr account, as the app generates its own signing identity, separating private documentation from public profiles. The developer emphasizes that no data is collected from this app, with the tagline 'Capture. Prove. Verify.' Potential use cases include contractors documenting work, landlords recording property conditions, homeowners capturing insurance damage, and delivery workers documenting drop-offs. Critics question whether the app uses perceptual hashing for scene verification, but the developer clarifies it employs a file-based hash. While some argue the method is fragile due to potential file alterations, the app's focus on file integrity rather than scene authenticity makes it useful for legal and documentation purposes. The Slashdot article highlights both the app's technical approach and its practical applications in everyday scenarios.

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.

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