Information services

• In contrast to unidirectional distribution services, interactive information services work on the basis of handling direct requests by the system user. The user normally authenticates himself or herself to the system and can then access the system functions and the data contents. The communications may be eavesdropped and/or manipulated by unauthorized third parties. Protection mechanisms for confidentiality, integrity, and authenticity, as well as copyright, can be implemented in a user specific way, because there is always exactly one communication relationship between the provider and the consumer the following section describes one example: video archives.

• Video Archives: When considering video archives, we first have to determine whether or not the video data stored include confidential contents in the sense of the data privacy law, e.g. in police archives. if it is necessary to constantly access the data in real time, then a complete encryption of the archived data should be considered, to ensure that the data are protected, also in case of burglary or hardware theft. However, when the constant availability of the data should be kept in a closed system or a system properly shielded from the outside with corresponding access control and authentication of all users, to ensure sufficient protection.

• Many public or private film archives, however, contain video data with non-confidential material which has been publicly distributed, e.g on the radio. An encryption of such video data is not aimed at protecting the contents against eavesdropping, but rather represents a possibility of controlling access to the video material. alone the gigantic quantities of film material. e.g. of the size of the order of several terabytes, would make it impossible or meaningless to fully encrypt the archived material. An encryption method used in such a case should have the following properties:

1. The method should work at high speed, due to the enormous data volume, to allow encryption of a full archive within an acceptable time and the calculation of hardware cost.

2. The encrypted video data should allow fast retrival and other database operations, so that the protected data can be found within the repository and reused.

3. The space requirement for video data should not increase when this data is encrypted, to avoid any resulting resorting and copying of the video material in the archive database. It is often meaningful for such system to leave the video data unencrypted and to develop a sophisticated access strategy to the archive system instead.