In tense situations, often there are requirements to communication current messaging systems aren’t able to meet. While systems like Signal offer cryptographic protections to ensure confidentiality, authenticity, and more, using a separate messaging system sometimes is not possible. Those systems might be censored in a given region, it might be illegal to have their apps installed (and one could get into trouble in road checks), or communication via, e.g., WhatsApp is preferred, because using it is free in that country and all contacts are there. WhatsApp officially states that it is using end-to-end encryption, but this can’t be confirmed independently.
In addition to that, some high-risk users need additional protections against physical attacks on their devices. To someone inspecting their devices, it should not be visible at the first glance that some secret communication is happening.
Oculta (Spanish for „hidden“) is a free and open-source Android application that allows to have cryptographically protected communication that is exchanged in a hidden manner via existing messaging systems like WhatsApp, Telegram, or email. For this, messages composed in Oculta are protected using state-of-the-art cryptography and hidden inside images or text using techniques from steganography.