Digital Signing of VoIP Communication

A unique method for the digital signing of Voice over IP communication was developed in the self funded research project VoIPS. The signature is applied during the conversation and does not interfere with the quality of the call. The VoIP Signature (VoIPS) technology introduces non-repudiation into calls as well as continuous authentication of callers, and allows to enter into binding contracts by phone without having an actual witness present.

Internet telephony combines conventional telephony technology with information technology. The fusion of these two technologies pioneers new possibilities for companies to develop business models and functionalities in this domain. This opens new application areas for well-known tools, technologies, and methods from the IT-Security. One example is the archiving of voice communication to establish non-repudiation as it is required in the areas of aviation, broadcast radio, or telephone banking.

For the application area of voice recording Fraunhofer SIT implemented software to demonstrate the capabilities of the VoIPS technology. The software creates legally binding recordings of conversations which can be archived in an appropriate, long term archive. The underlying use case aims to establish legally binding contracts on the technological foundation of VoIP between unacquainted partners without witnesses.

Digital signatures provide the technological foundation for the VoIPS technology and provide the well- known means to reach level of security required to establish non-repudiation. In the case of VoIP communication IP data packets are transferred between the involved parties. VoIPS defines intervals and signs all packages transmitted within these intervals. To protect the ordering and coherence of the signatures a Hash value of each interval is created and included in the meta data of the next package. This results in a strong cryptographic chain. At the same moment VoIPS bundles both channels between the participants so it can be applied also in full duplex environments without restrictions.

VoIPS is well suited for all situations where companies, authorities, or even private individuals want to store digital communication tamper-proof to circumvent later legal uncertainties. This holds true for telephone banking as well as the oral documentation in a medical operation. In combination with other technologies like biometrics or smart cards VoIPS is a corner stone for legally binding contracts and documentation in digital communication scenarios.