The Republic's Health Minister Stephen Donnelly said the new Covid-19 tracker app has "privacy at its core" as he appealed to people to download it.
The app has been downloaded by more than 250,000 people since it became available last night.
Mr Donnelly said "today is a good news day" for the Republic's fight against Covid-19.
"Please download this app," he said.
The app informs you if you have been in close contact with someone who has tested positive for Covid-19.
Mr Donnelly said he understands people's concerns about data privacy regarding the tracker.
He said: "Those concerns are very real and reasonable. The app has been developed with privacy by design at its core. We are also encouraging friends and families to help those that may not be as technically literate, to download and use the app."
"We've ensured that from the very first version, the app is available in English and in Irish, and we are very much open to incorporating other languages in future upgrades as we receive feedback."
Mr Donnelly said privacy is built into the app at every point in the process.
He said if someone tests positive for Covid-19, they will receive a phone call where they will receive advice.
"If you have the tracker app, you will be asked your permission for your phone to share the close contact information. You can say no at this point. The app is opt in - no-one is being forced to download or use it."
HSE chief executive Paul Reid confirmed that as of this morning, the app has been downloaded by 250,000 people since it was launched on Monday night.
Mr Reid said he "had a dream that we had a quarter of a million users of this app".
"I can confirm that it isn't a dream, we have that many users. It is a phenomenal achievement."
Mr Reid appealed to people to tell everyone in their networks to download it.
He said: "If every one of us asks all of our network to download the app today, we will capture everyone we need. If everyone asks everyone in their network to download this app - that's the level we're looking for in uptake."
Mr Reid added the app is not a "silver bullet" and said the app will complement the existing contact tracing system.
He said the app has cost 850,000 euro to develop and that this is "on the margins" in terms of the overall health spending on coronavirus.
Acting chief medical officer Ronan Glynn said that until there is a vaccine against Covid-19, social distancing, hand hygiene, and mask wearing will be key to battling the virus.
He said: "The Covid-19 tracker app will be a very important addition to this and will increase our capacity to combat the spread of the disease."
Dr Glynn added: "We realise that high uptake requires public trust and confidence... This is why such attention has been paid to data protection and privacy."
He said research shows that a large majority of the Irish public said they would download the app, and he is confident people will get on board.
Mr Donnelly said the Covid-19 tracker app's coverage is "effectively all-island" and that it will work everywhere in the country, regardless of internet access.
"The app works with Bluetooth technology - it works phone-to-phone. If two people meet on top of Carrauntoohil in Co Kerry for 15 minutes - the phones will log that.
"The app is not active in the six counties (of Northern Ireland) right now. We would very much like it to be across the entire island, but certainly for now, anyone who is crossing the border should absolutely download the app."
No new Covid-19 deaths were reported yesterday in the Republic while there were four more confirmed cases.
