Vesselin Tzvetkov

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The rapid growth of the SIP implementations clearly shows that the classical PSTN network will be exchanged by Internet telephony. All Service Providers (SP) are currently deploying SIP infrastructure for offering the next generation networks. The implementations and network concepts used by the SP are different then the original designed in SIP standard.(More)
Internet is major communication media and staying "online" becomes a key requirement. Commonly, the broadband access and enterprise networks involve devices with dynamic NAPT(NAT) and statefull firewalls functionality. Keeping open connection behind such an intermediate device is not a trivial task. The intermediate device closes the connection without(More)
The public key infrastructure (PKI) is an important part of almost all security implementations from secure portals for banks and e-shops to VPN devices. In spite of its strengths there is a critical design issue causing a single point of failure for the PKI infrastructure. Once the CA (certification authority) key has been stolen, the integrity of the(More)
  • V. Tzvetkov
  • 2008 Third International Conference on…
  • 2008
The mobile usage of Internet is characterized by frequent changes of the access network and consequently, changes of the application's IP address or port. Intermediate NAT devices can exchange additionally the transport and network headers. Not using the current IP and port parameter leads to lost packets and service interruption. To overcome these(More)
  • V. Tzvetkov
  • 2008 Third International Conference on…
  • 2008
The Internet is becoming the dominating medium for modern communications. The SIP protocol delivers the majority of VoIP services. The SIP usage in mobile environments becomes reality due to the widespread of portable devices together with dynamic lifestyle. Unfortunately, SIP is not designed to work in mobile environments where access network and IP(More)
The Public Key Infrastructure (PKI) is an important part of almost all security implementations, from secure portals for banks and e-shops to vpn devices. Although it has advantages, there is a critical design issue due the single point of failure of the root (CA) certificate. This issue is solved by decentralization of the infrastructure. Since a lot of(More)
Abstract- The security of complex networks with multiple elements is very difficult to evaluate and characterize by numbers. The interaction between the network elements, the different layer topologies and the numerous features makes the security quantification almost impossible. On the other side, the lack of security benchmarking is very problematic for(More)
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