A process for storing data on a central server, wherein there is a multitude of users each having a user password which is used at least for generating a user key and wherein at least one client with stored data is assigned to each of at least some of said users and wherein at least some of said data are assigned as required to at least one data block to be uploaded and wherein, based on a unique data block ID value, each data block is compared to the data blocks on the server to find out whether a corresponding data block is already present on the server and wherein the data blocks which are not present on the server are uploaded to the central server and wherein a data-data block list, based on which data can be regenerated in their original form in a data recovery step when requested by the user from the central server, which is to be uploaded is created and uploaded to the central server, characterized in that the following steps are carried out for each unencrypted data block on the client to identify the data blocks to be uploaded to the central server and create the data-data block list to be uploaded to the central server: - generating a data block key exclusively based on the unencrypted data block using a key generation protocol so that the user password and other user-relevant data are not used for generating said key, - encrypting the unencrypted data block based on said generated data block key using an encryption protocol to obtain an encrypted data block, - generating a unique data block ID value based on the unencrypted data block and, optionally, on the information retrieval and/or key generation and/or encryption protocol and assigning said data block ID value to the encrypted data block using a data block ID generation protocol predefined for said user, - transmitting said unique data block ID value from the client to the central server to receive a response indicating whether the encrypted data block assigned to said data block ID value is already present on the central server and uploading the encrypted data block if it is not already present on the central server, - adding said unique data block ID value to the data-data block list which is to be uploaded to the central server, - adding said data block ID value and said data block key into a data block-key list, if said data block ID value is not already included in said data block-key list, wherein it is possible for said data block-key list to be part of the data-data block list, and in that based on all identified data blocks to be uploaded the following steps may be carried out: - encrypting the data-data block list using a data-data block list key which is generated using a data-data block list key generation protocol which is managed by the user and only known to said user, - encrypting said data block-key list using the user key, - uploading the encrypted data-data block list and the encrypted data block-key list from the client to the central server, the unencrypted data blocks, the unencrypted data-data block list, the unencrypted data block-key list and the generated data block keys and the user key remaining on the client, the server sending data which are stored on the server in their encrypted form and cannot be decrypted by the server to the client in said data recovery step, so that data can only be recovered on the client. - generating a data block key exclusively based on the unencrypted data block using a key generation protocol so that the user password and other user-relevant data are not used for generating said key, - encrypting the unencrypted data block based on said generated data block key using an encryption protocol to obtain an encrypted data block, - generating a unique data block ID value based on the unencrypted data block and, optionally, on the information retrieval and/or key generation and/or encryption protocol and assigning said data block ID value to the encrypted data block using a data block ID generation protocol predefined for said user, - transmitting said unique data block ID value from the client to the central server to receive a response indicating whether the encrypted data block assigned to said data block ID value is already present on the central server and uploading the encrypted data block if it is not already present on the central server, - adding said unique data block ID value to the data-data block list which is to be uploaded to the central server, - adding said data block ID value and said data block key into a data block-key list, if said data block ID value is not already included in said data block-key list, wherein it is possible for said data block-key list to be part of the data-data block list, - encrypting the data-data block list using a data-data block list key which is generated using a data-data block list key generation protocol which is managed by the user and only known to said user, - encrypting said data block-key list using the user key, - uploading the encrypted data-data block list and the encrypted data block-key list from the client to the central server,