Securely booting a computer from a user trusted device

A method for allowing a computer to boot from a user trusted device, wherein:

• the computer comprises a long-term data storage device storing operating system (OS) services;
• and
• the user trusted device is separate from the computer and stores:
• a boot loader, detectable and executable by a firmware of the computer, upon detecting a connection of the user trusted device to said computer;
• an OS loader designed to load an OS, of the computer;
• and
• one or more crypto drivers designed for allowing access to the OS and data stored encrypted on said long-term data storage device of the computer;
• wherein the user trusted device is designed to prevent unauthenticated access of each of:
• the boot loader;
• the one or more crypto drivers;
• and the OS loader, as stored thereon, the method comprising:
• upon connection of the user trusted device to the computer, letting the boot loader be detected by said firmware for a subsequent execution of the boot loader at least partly at the computer to cause to transfer the OS loader of the user trusted device from the user trusted device to the computer, by loading the OS loader into a main memory of the computer, without storing any part of the loaded OS loader on the long-term data storage device of the computer;
• and
• executing the transferred OS loader at least partly at said computer, to cause to execute the one or more crypto drivers of the user trusted device for access to said OS and said data stored encrypted on said long-term data storage device by providing at least one cryptographic key from the user trusted device to the one or more crypto drivers during the execution of the one or more crypto drivers, to start said OS services and complete booting of the computer.