Every check in one place

Hidden messages in images come in many forms, and puzzle makers mix them. The Image analyzer runs all of CacheCrack's image checks at once and lists anything interesting at the top.

It reads the photo's details, including GPS location, comments, IPTC captions and XMP fields. It scans the whole file for other files tucked inside it, like a ZIP after the end of a JPEG or a PNG hidden in a comment, and lets you download each one. It shows the small thumbnail many cameras store inside the file, which sometimes still shows the picture before it was edited. It tests the pixel bits for hidden text the way the zsteg tool does, and shows every bit plane so you can spot a hidden picture.

Codes drawn in the picture

Many puzzle images are simply a code drawn as a picture. CacheCrack reads rows of arrows, Morse dots and dashes, tap code, braille dots, pigpen symbols, dice, Mayan numerals and POSTNET barcodes, plus runes, ogham and semaphore drawn the way CacheCrack's own tools draw them, and passes what it finds to the cipher identifier. So it can tell you, for example, that the picture is the Matrix Walker cipher and spells A, or that the pigpen letters are themselves a Caesar cipher and what they say. It reads typed and drawn symbols, dark on light or light on dark. Pigpen is read with the usual layout, as in the Pigpen tool, so a puzzle with its own layout may come out scrambled. Semaphore pictures from other sites vary too much to read reliably, so use the Semaphore tool for those.

Reading text in the picture

Press Read text in this picture to turn letters and numbers in an image into text you can copy, such as a cipher printed on a sign or a screenshot of a puzzle. The result goes straight to the cipher identifier. The first time, this downloads the text reader, about 6 MB, from CacheCrack itself. After that it works offline. Text reading can confuse look-alike characters, like l and I or O and 0, so check anything that looks off. Very small text is harder to read, so use the largest or original copy of the image you can.

PNG size tricks

A classic puzzle trick is to change the height written in a PNG's header so part of the picture is cut off. Every PNG header carries a checksum, so CacheCrack works out the real size from it and shows the repaired picture. If the checksum was fixed too, it counts the rows in the image data instead.

Private by design

Many online analyzers upload your image to their server. CacheCrack does all of this in your browser, so your puzzle images never leave your device, and it keeps working offline.

steghide

JPEGs and BMPs are also checked for files hidden with steghide, using an empty passphrase and a list of common guesses. For other passphrases, use the steghide tool.

Two pictures, one secret