A family in a displaced persons camp lines up to get weekly food aid, but first someone scans their irises and fingerprints to verify their identities.

That sounds like it could be a scenario out of a dystopian novel — tying lifesaving supplies to biometric readings — rife with possibilities for abuse. But it’s actually becoming a crucial component of relief services in refugee camps, war zones, and other places where the United Nations operates.

In Sanaa, Yemen’s capital, concerns by political groups controlling the city over the potential privacy violations of a biometric reading system have disrupted the World Food Program’s ability to distribute food supplies to vulnerable populations in what has become the world’s worst humanitarian crisis, according to the humanitarian news website Devex.

An estimated 850,000 people could be denied food aid in the city because of these apprehensions. The WFP currently aims to deliver food to more than 12 million people in the country, which has been ravaged by a civil war since 2015. 

“The integrity of our operation is under threat and our accountability to those we help has been undermined,” WFP said in a statement announcing the partial suspension. “WFP has repeatedly appealed to the Sanaa-based authorities to grant us the space and freedom to operate according to the principles of humanity, impartiality, neutrality, and operational independence, which guide our work in 83 countries around the world.”

The Houthi, an ethnic group that controls most of the country, have told the UN that collecting biometric information goes against Yemeni law and has raised flags about the potential for privacy breaches.

Read More: UN May Suspend Aid to Yemen After Rebels Steal Food Donations

The WFP, on the other hand, argues that biometric information would allow it to more effectively deliver aid, reach the most vulnerable populations, and prevent the theft of food supplies. In recent months, the WFP has consistently reported that food aid has been stolen by Houthi groups and sold for profit.

The WFP also insists that all data is securely held and protected from misuse by other parties, including potentially hostile state governments.

UNHCR, the UN refugee agency, has deployed biometric scanning programs throughout the world in refugee camps and argues that the system gives people who have potentially lost paperwork and identification cards a chance to reclaim their identities and transition into a more stable living arrangement. The system also allows the UN to ensure families are getting the right amount of food to survive and thrive. 

Farah, 4, from Homs, #Syria, being registered using biometric iris scanning technology at UNHCR Amman #Jordanpic.twitter.com/BMWomtCtL6

— UNHCR, the UN Refugee Agency (@Refugees) May 6, 2014

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The rollout of biometric databases has occasionally faced resistance. For example, Rohingya refugees in Cox’s Bazar, Bangladesh, staged a hunger strike to oppose the collection of bodily information for fear that it would then be misused by the government in Myanmar, according to Devex. 

Humanitarian experts who spoke with Devex said that such programs need to be fully transparent with the targeted communities to be successful — otherwise, the act of collecting bodily data can seem overly invasive. 

If the benefits and privacy safeguards are explained, then there can be a smoother implementation of such programs. 

Even if there’s community buy-in and support from local political actors, carrying out a biometric scanning program is challenging on a few levels, experts argue. First, it’s difficult to enroll and scan everyone who requires aid in the program, especially when new people assimilate into the affected population all the time. Second, the system depends on reliable technology and oversight, which may be compromised in warzones and other humanitarian settings. 

#Uganda: UNHCR launching major biometric verification exercise of all refugees https://t.co/GIw54DMDPI

— UNHCR, the UN Refugee Agency (@Refugees) February 21, 2018

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The WFP isn’t backing down from its intention to enroll people in Sanaa in a biometric database because other efforts to properly deliver aid have been thwarted. 

“Too many Yemenis have suffered for too long during this ongoing conflict,” WFP said in a statement. “We will continue to seek cooperation from the Sanaa-based authorities and we remain optimistic that a way forward can be found. We are ready to immediately resume food distributions once we reach agreement on an independent beneficiary identification exercise and the roll out of a biometric registration system.”