Secret key management and dynamic security coding system

Digital information transmission systems must satisfy two requirements: reliability and confidentiality. In terms of reliability we tend nowadays to the Shannon´s capacity, i.e. the limit of errorless data rate. Concerning the confidentiality of transmissions, a perfect secrecy limit was also defined by Shannon but this aspect of the Shannon´s work was less adressed. Nevertheless, in order to enhance the security of transmissions, especially with wireless systems, an encryption is often used. In this contribution, we present an encryption scheme that jointly protect the exchange of information against eavesdropper as well as errors due to the propagation channel. The key controlling the encryption scheme is dynamically generated and propagation measurements will be used to illustrate the importance of the key length.