A Note on Keys and Keystreams of Chacha20 for Multi-key Channels
In this paper we analyze the keystreams generated by the Chacha20 stream cipher. We also compare these to the ones generated by its predecessor, the RC4 stream cipher. Due to the proposed multi-key channels in the upcoming TLS 1.3 standard we analyze the behavior of the keystream in the boundary case where there is a single bit difference between two keys used for the initiation of the stream cipher algorithms. The goal is to check whether a single bit change in the key has any predictable influence on the bits of the keystream output.
Algorithmic Complexity Vulnerability Analysis of a Stateful Firewall
Algorithmic complexity vulnerabilities are an opportunity for an ad-versary to conduct a sophisticated kind of attack i.e. on network infrastructure services. Such attacks take advantage of worst case time or space complexity of algorithms implemented on devices in their software. In this paper we address potential risks introduced by such algorithmic behavior in computer networks in particular on a stateful firewall. First we introduce the idea and theoretical background for the attack. We then describe in full detail a successfully con-ducted attack which takes advantage of the worst case computational complexi-ty of O(n2) of a hash table data structure used to store active sessions. The …