Method for server assisted keystore protection

A method to access a data store previously locked using a passphrase from a device, said method including the preliminary steps of:

• for the device, requesting the user to enter a personal code on the device;
• for the device, calculating a first function of at least the personal code;
• for the device, sending, for storage, said first function to a server having access to the passphrase;
• said method further comprising the following steps, when the user requests access to the data store:
• for the device, requesting the user to enter the personal code,
• for the device, generating an access code by applying said first function to at least the entered personal code;
• for the device, sending out, to the server, at least an identifier of the device and the access code;
• for the server, comparing the access code with the preliminary received first function;
• for the server, if the access code is correct, returning the passphrase to the device;
• for the device, unlocking the data store using the received passphrase in combination with the entered personal code.