Amid ever-increasing government internet control, surveillance, and censorship in Iran, a new Android app aims to give Iranians a way to speak freely.

Nahoft, which means “hidden” in Farsi, is an encryption tool that turns up to 1,000 characters of Farsi text into a jumble of random words. You can send this mélange to a friend over any communication platform—Telegram, WhatsApp, Google Chat, etc.—and then they run it through Nahoft on their device to decipher what you’ve said.

Released last week on Google Play by United for Iran, a San Francisco–based human rights and civil liberties group, Nahoft is designed to address multiple aspects of Iran’s internet crackdown. In addition to generating coded messages, the app can also encrypt communications and embed them imperceptibly in image files, a technique known as steganography. Recipients then use Nahoft to inspect the image file on their end and extract the hidden message.

Iranians can use end-to-end encrypted apps like WhatsApp for secure communications, but Nahoft, which is open source, has a crucial feature in its back pocket for when those aren’t accessible. The Iranian regime has repeatedly imposed near-total internet blackouts in particular regions or across the entire country, including for a full week in November 2019. Even without connectivity, though, if you already have Nahoft downloaded, you can still use it locally on your device. Enter the message you want to encrypt, and the app spits out the coded Farsi message. From there you can write that string of seemingly random words in a letter, or read it to another Nahoft user over the phone, and they can enter it into their app manually to see what you were really trying to say.

“When the internet goes down in Iran, people can’t communicate with their families inside and outside the country, and for activists everything comes to a screeching halt,” says Firuzeh Mahmoudi, United for Iran’s executive director, who lived through the 1979 Iranian revolution and left the country when she was 12. “And more and more the government is moving toward layered filtering, banning different digital platforms, and trying to come up with alternatives for international services like social media. This is not looking great; it’s the direction that we definitely don’t want to see. So this is where the app comes in.”

Iran is a highly connected country. More than 57 million of its 83 million citizens use the internet. But in recent years the country’s government has been extremely focused on developing a massive state-controlled network, or intranet, known as the “National Information Network” or SHOMA. This increasingly gives the government the ability to filter and censor data, and to block specific services, from social networks to circumvention tools like proxies and VPNs.

This is why Nahoft was intentionally designed as an app that functions locally on your device rather than as a communication platform. In the case of a full internet shutdown, users will need to have already downloaded the app to use it. But in general, it will be difficult for the Iranian government to block Nahoft as long as Google Play is still accessible there, according to United for Iran strategic adviser Reza Ghazinouri. Since Google Play traffic is encrypted, Iranian surveillance can’t see which apps users download. So far, Nahoft has been downloaded 4,300 times. It’s possible, Ghazinouri says, that the government will eventually develop its own app store and block international offerings, but for now that capability seems far off. In China, for example, Google Play is banned in favor of offerings from Chinese tech giants like Huawei and a curated version of the iOS App Store.