Abstract: A method for providing and checking the validity of a virtual document on a first computer system is disclosed. The virtual document is provided by means of a mobile second computer system for a first computer system. The method includes receiving a password-protected storage address of a first database at which the virtual document can be read, reading the virtual document, displaying the virtual document on a display of the first computer system, receiving a unique second identifier of the mobile second computer system, calculating a third identifier using the received second identifier and a hash value of the virtual document, identifying the database entry of the second database in which a first identifier of a first pairing consisting of the mobile second computer system and the first virtual document is stored, comparing the calculated third identifier with the first identifier stored in the identifier database entry.

Abstract: A method for providing and checking the validity of a virtual document on a first computer system is disclosed. The virtual document is provided by means of a mobile second computer system for a first computer system. The method includes receiving a password-protected storage address of a first database at which the virtual document can be read, reading the virtual document, displaying the virtual document on a display of the first computer system, receiving a unique second identifier of the mobile second computer system, calculating a third identifier using the received second identifier and a hash value of the virtual document, identifying the database entry of the second database in which a first identifier of a first pairing consisting of the mobile second computer system and the first virtual document is stored, comparing the calculated third identifier with the first identifier stored in the identifier database entry.