The public have been urged to download the upcoming NHS coronavirus contact-tracing app, amid questions over the privacy and security safeguards it will have.

The new updates on the working of the app comes as the first testing on the Isle of Wight begins, with NHS bosses hoping that the app will become a key part of the government's "test, track and trace strategy".

The app works by using a phone's Bluetooth connection to look for other phones that have it installed. It logs the phones – and people – that a person has been in contact with, and anonymously alert them if anyone in that network starts showing the symptoms of covid-19.

Experts have warned that the app's usefulness will depend largely on how many people download it, though those behind the app have said that even with a limited take-up it will still play an important part in fighting the spread of the disease and allowing the UK to come out of lockdown.

"We do have some uncertainties about how many people will download the app, and it will be important that a significant proportion of the population downloads the app for it to have the greatest chance of giving us additional oomph in the contact tracing space, which in turn will give us additional room for manoeuvre in terms of other social distancing easements that we can consider in the weeks and months to come," said Professor Jonathan Van-Tam, deputy chief medical officer for England.

"It's highly unlikely that the Covid-19 virus is going to go away, very likely that we are going to have to live with this virus in our communities to a greater or lesser extent until we find long-term solutions such as effective vaccines.

"Therefore, testing and contact tracing is going to have to become part of our daily lives for the future."

Those who have worked to develop it say that the app has been built to protect the privacy of the people who use it. Privacy and security concerns have been one of the key questions about the app.

"As we have developed the app, we've put privacy right at the heart of it and the way it works," said Matthew Gould, chief executive of NHSX.

"The app is designed so that you don't have to give it your personal details to use it... it doesn't know who you are, it doesn't know who you've been near, it doesn't know where you've been."

Gould also defended the decision by the NHS to use a centralised design for the app, meaning that information will be sent to the health service for storage rather than kept on individual users' phones. He said that the decision had been made because health experts could use that same information for future research.

The decision to build the app in such a centralised way has led to criticism from some privacy campaigners, who have cautioned that it could put the data at risk of being stolen or manipulated if hackers are able to access it.

Mr Gould confirmed the app collected no specific personal data from users, instead relying on the anonymous keys assigned to each app user which could not be linked back to them. That will limit the use of the data to any hacker who manages to gain access to it, he claimed.

"The app is designed so you don't have to give it your personal details to use it - it does ask for the first half of your postcode but only that," he said.

"You can use it without giving any other personal details at all – it doesn't know who you are, it doesn't know who you've been near, it doesn't know where you've been."

The National Cyber Security Centre (NCSC), which has helped with the app's development, said privacy-preserving gateways had been built into the system so that all app data would be kept separate from other NHS data and to prevent individuals from being identified.

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