Abstract: Method and apparatus for preventing illegal copying of copyright material. Encrypted data is transmitted from a first computer to a second computer, and the decryption key has to be requested each time the user want to gain access to the data in an unencrypted form. The encryption key is subsequently rendered unfit for use and/or the decrypted data is rendered unfit for use. The decryption key may be stored in a non-accessible part of a hardware processor of the second computer. Access to the data in an unencrypted form, e.g. the number of copies, may thus be controlled. Further, a method of distributing electronic data from a number of publishers to a number of recipients. Each publisher makes data available from e.g. a web site, and the recipients may purchase the data via a global computer network. The data is distributed in a safe manner as described above. Makes it possible to publish small editions of data while still protecting the copyright.