Signing with a Qualified Certificate is the recommended signing method for diaries maintained under the Construction Act. A signing certificate can be obtained from a qualified trust service provider, such as PostSignum, a subsidiary of Česká pošta, or První certifikační autorita.

[PostSignum](https://www.postsignum.cz/?utm_source=chatgpt.com)
[První certifikační autorita (I.CA)](https://www.ica.cz/?utm_source=chatgpt.com)

The signing certificate can be stored on your computer, mobile device, token, or another secure storage device.

To sign with a qualified certificate from the web application, you need to install an auxiliary application on your computer.

To sign in the mobile application, you need to transfer the certificate to your mobile device and import it into the Buildary mobile application.