ИИТ Пользователь ЦСК-1 is a free Android application developed by АТ ІІТ. This utility and tool app is designed to manage personal keys and certificates of open user keys of ЦСК users. It also provides users with the ability to create electronic signatures and encrypt their data. The app offers a wide range of features, including key management, access to ЦСК certificates and servers, access to other user certificates, and the ability to protect user files. Users can generate keys, write private keys on NCI, and create certificate formation requests. They can also verify the certificate's formation, backup the private key, change the password of the private key, and destroy the private key on NCI. In addition, users can access the certificates stored in the file repository, search for certificates using the OCSP protocol, and determine the certificate's status using SOS and the OCSP protocol. The app enables users to sign files, verify file signatures, and encrypt and decrypt files.