The app will be available to the public at the same time as it is being presented. The German government presented the app on Tuesday and it is available for use immediately.

Apple and Google have already created the conditions in May for the app to be downloaded to iPhones and Android devices. The iPhone requires that the current iOS 13.5 must be installed. This will not work on older iPhones 5, 5s or 6. On Android devices a 6s version is required for loading the app. Google Play Services must also be running on the devices, which is not the case with the latest Huawei models.

Theoretically yes. For example, key fobs could be equipped with technology for corona warning functions. Such an alternative has not yet been proposed by the federal government for the warning app. However, it is quite possible that such alternative options will become available at a later date.

Practice will show that. On a positive note, the federal government, together with SAP and Telekom, the companies commissioned to develop the app, has published the programming data in advance to give experts and interested laypersons who are not close to the federal government the chance to test it. According to the federal government, 285 suggestions for improvement have been received so far. This open procedure has led to the involvement of the critics, whose concerns have contributed to improving the product.

As soon as two users get close to each other at a distance of about two meters and remain at this distance for 15 minutes or longer, the apps exchange data via Bluetooth. If one of them performs a corona test due to symptoms or other indications and the result is positive, he has the possibility to feed the test result into his warning app. This app will then anonymously inform all stored contacts. Loading the app as well as the responsible handling of your own test result and the feeding of the data is voluntary. The app is not automatically loaded onto the phones. The health authorities have no access to the data.

You should immediately ensure you have a corona test done. To do this, you should either contact your family doctor, the doctors' hotline 116117 or the relevant health authority. The warning does not automatically lead to quarantine. However, it would make sense to isolate yourself if possible until the test result is available. An official quarantine can only be imposed by the public health department.

The decision to store the data collected by the app decentrally, i.e. only on the smartphone owners' data, was an important step to protect the users' data. In addition, the decision-making authority over the data remains with the affected parties. Anyone who tested positive for Corona must enter their results into the app themselves so that their own contact persons know about them. No server, no public health department and no regulatory authority will know about it.

There is no fundamental criticism on the part of data protectionists. The Federal Commissioner for Data Protection, Ulrich Kelber, had already incorporated some of the desired changes into the development. "It is particularly important to me that the relevant documents on data protection, especially the data protection impact assessment, are ready when the app is launched," he said last week. They should be made public from day one in order to create trust and acceptance among the population. A privacy impact assessment must be prepared by the manufacturers and submitted to the authorities if they see any risks in data processing. "I am confident that the companies and authorities involved will implement our recommendations as quickly as possible," said Kelber. The documentation and legal texts available so far make a solid impression overall.

Despite recent improvements, IT experts see a possible gateway for abuse when using a particular hotline. The hotline is necessary because not all Corona test labs have a digital connection to the app yet. If a person using the App is tested in such a laboratory and the test is positive, the laboratory cannot automatically and anonymously feed the result into the App, so that the user can warn other people. The infected person has to call a hotline and answer test questions from call center staff to ensure that the person has actually tested positive. The questions and answers must not allow any inference about the person. However, because this is the case, the questions could be answered by another person, who could then trigger a false warning message in the app. Whoever calls the hotline also runs the risk of disclosing their own telephone number.

Experts estimate that 60 percent of the population should participate. Minister of Health Spahn is pragmatic and says that everyone who downloads the app helps. For the first few weeks, he hopes for several million participants.

The development of the app has cost about 20 million Euro. The operation will cost between 2.5 and 3.5 million euros per month. A large part of the operating costs are accounted for by the hotline, which not only releases positive test results for uploading in the app, but is also available to answer any other questions.

So far only in those cases in which, for example, citizens from Germany meet in holiday resorts who use the Corona-Warn-App. The app is not yet compatible with other European developments. But we are working on it.

It would make sense to download the app to the device you always carry with you. There is no way to link the contacts of two smartphones in case of a positive corona test.

(Original text: Eva Quadbeck and Jan Drebes, Translation: Mareike Graepel)