Catch the leaker.

You send one private photo to someone you trust. Weeks later it turns up in a WhatsApp group you were never in. Save that copy, drop it into PrivateMark, and it names exactly who you sent it to, from an invisible, per-recipient watermark woven into their copy alone. All on-device. No servers, no accounts.
Plus Hidden Photo: send a real picture disguised as an innocent cover only your trusted contact can open.