Nitrokey is an USB key to enable highly secure encryption and signing of emails and data, as well as login to the Web, networks and computers. Other than ordinary software solutions, the secret keys are always stored securely inside the Nitrokey. Their extraction is impossible which makes Nitrokey immune to computer viruses and Trojan horses. The user-chosen PIN and the tamper-proof smart card protect in case of loss and theft. Hardware and software are both available as Open Source to allow verifying the security and integration with other applications.