A computer implemented method, server computer and computer program for securely storing a data file via a computer communication network. The method includes: providing a computer device of a user with code for providing a unique user name for the user; asking the user for a password; generating an asymmetric key pair for the user having one public key and one private key; encrypting the private key via the hash of the password; generating a file-specific symmetric key specific for the data file; encrypting the data file via the file-specific symmetric key; encrypting the file-specific symmetric key via the public key of the user; where the code is executed by a web browser on the computer device. The server is then receiving the encrypted data file, the encrypted file-specific symmetric key, the encrypted private key of the user and the public key of the user from the computer device.