A method for generating a pseudonym with the help of an ID token for a user, wherein the ID token is assigned to the user and the ID token has a protected memory area for storing at least one private key of a first asymmetric cryptographic key pair assigned to the ID token, and wherein the pseudonym of the user is assigned to a service computer system from a set of service computer systems (150, 150', 150",...), said method having the following steps: - calling up a website of one of the service computer systems, selected by the user, with a web browser of a user computer system via a network, - generating a request by the selected service computer system for the pseudonym of the user, - transmitting the request from the service computer system to an ID provider computer system via the network, - generating an ID token pseudonym by the ID token by cryptographic derivation of the ID token pseudonym from the private key and the public key, - temporarily storing the ID token pseudonym in the ID token, - transmitting the ID token pseudonym from the ID token to the ID provider computer system with end-to-end encryption via the network, - accessing a memory (186, 188) by the ID provider computer system with the help of the ID token pseudonym in order to read a virtual pseudonym (vP) of the user assigned to the ID token pseudonym, - deriving the pseudonym (RID') of the user assigned to the selected service computer system from the virtual pseudonym of the user by means of a cryptographic function specific for the selected service computer system by the ID provider computer system, - signing the derived pseudonym by the ID provider computer system, - transmitting the signed pseudonym from the ID provider computer system to the selected service computer system via the network, wherein each of the service computer systems is assigned a one-way function, so that the ID provider computer system, for derivation of the pseudonym (RID'), accesses the one-way function assigned to the selected service computer system in order to derive the pseudonym from the virtual pseudonym with the help of this one-way function. - calling up a website of one of the service computer systems, selected by the user, with a web browser of a user computer system via a network, - generating a request by the selected service computer system for the pseudonym of the user, - transmitting the request from the service computer system to an ID provider computer system via the network, - generating an ID token pseudonym by the ID token by cryptographic derivation of the ID token pseudonym from the private key and the public key, - temporarily storing the ID token pseudonym in the ID token, - transmitting the ID token pseudonym from the ID token to the ID provider computer system with end-to-end encryption via the network, - accessing a memory (186, 188) by the ID provider computer system with the help of the ID token pseudonym in order to read a virtual pseudonym (vP) of the user assigned to the ID token pseudonym, - deriving the pseudonym (RID') of the user assigned to the selected service computer system from the virtual pseudonym of the user by means of a cryptographic function specific for the selected service computer system by the ID provider computer system, - signing the derived pseudonym by the ID provider computer system, - transmitting the signed pseudonym from the ID provider computer system to the selected service computer system via the network,