Blockchains primarily enable credible accounting of digital events, e.g., money transfers in cryptocurrencies. However, beyond this original purpose, blockchains also irrevocably record arbitrary data, ranging from short messages to pictures. This does not come without risk for users as each participant has to locally replicate the complete blockchain, particularly including potentially harmful content. We provide the first systematic analysis of the benefits and threats of arbitrary blockchain content. Our analysis shows that certain content, e.g., illegal pornography, can render the mere possession of a blockchain illegal. Based on these insights, we conduct a thorough quantitative and qualitative analysis of unintended content on Bitcoin's blockchain. Although most data originates from benign extensions to Bitcoin's protocol, our analysis reveals more than 1600 files on the blockchain, over 99 % of which are texts or images. Among these files there is clearly objectionable content such as links to child pornography, which is distributed to all Bitcoin participants. With our analysis, we thus highlight the importance for future blockchain designs to address the possibility of unintended data insertion and protect blockchain users accordingly.

No abstract

No abstract

No abstract

No abstract

No abstract

The HIP Diet EXchange (DEX) is an end-to-end security protocol designed for constrained network environments in the IP-based Internet of Things (IoT). It is a variant of the IETF-standardized Host Identity Protocol (HIP) with a refined protocol design that targets performance improvements of the original HIP protocol. To stay compatible with existing protocol extensions, the HIP DEX specification thereby aims at preserving the general HIP architecture and protocol semantics. As a result, HIP DEX inherits the verbose HIP packet structure and currently does not consider the available potential to tailor the transmission overhead to constrained IoT environments. In this paper, we present Slimfit, a novel compression layer for HIP DEX. Most importantly, Slimfit i) preserves the HIP DEX security guarantees, ii) allows for stateless (de-)compression at the communication end-points or an on-path gateway, and iii) maintains the flexible packet structure of the original HIP protocol. Moreover, we show that Slimfit is also directly applicable to the original HIP protocol. Our evaluation results indicate a maximum compression ratio of 1.55 for Slimfit-compressed HIP DEX packets. Furthermore, Slimfit reduces HIP DEX packet fragmentation by 25 % and thus further decreases the transmission overhead for lossy network links. Finally, the compression of HIP DEX packets leads to a reduced processing time at the network layers below Slimfit. As a result, processing of Slimfit-compressed packets shows an overall performance gain at the HIP DEX peers.

No abstract