Humans have sent secret messages for millennia. A cousin to cryptography, steganography is the art and science of sending a secret message in the open by camouflaging the message carefully. Steganography can take many shapes, and its digital form often uses a digital image or video as a cover to hide the message. With a smartphone app, image steganography is easy to use, requires no expert knowledge of the science, and can be difficult to detect. To study mobile steganography properly, one must have a suitable database. This talk presents StegoAppDB, a database of digital photographs expressly created for studying mobile steganography, that will be used in NIST’s Open Media Forensic Challenge.