The Hidden Message inside the Photo. We launch the app and allow it to access the photos stored on our phone. We choose any picture: our cat, the pizza we ate the other night, a street scene. A text field then appears, letting us write the private message we want to send to a confidential source — for example: “Meet tomorrow at 11am, usual place.” Once the message is written, PixelKnot asks us to set a password and rates its strength. The app then creates a special JPEG image that contains the hidden note. With a tap, we can send the picture using any tool at hand — text message, email, WeTransfer or WhatsApp. The recipient sees only the cat or the pizza. But if they open the image with PixelKnot — and they know the password we set — they can read the concealed message. This two-step barrier, requiring both the app and the password, makes PixelKnot an effective tool.