Review – Cities and Agriculture

As people increasingly migrate to urban settings and with more than half of the world’s population now living in cities, it is vital to plan and provide for sustainable and resilient food systems which reflect this challenge. The book ‘Cities and Agriculture’ presents experience and evidence on key dimensions of urban food challenges and types of intra-and peri-urban agriculture, in 15 extremely well-researched and written chapters. The book has shed light on an urban challenge that has been ignored for a long time in urban studies as well as in urban policies and planning, i.e. food-provisioning. Neglecting the dynamics and sustainability of food provisioning in scientific research on sustainable urban development is a serious omission, because feeding cities arguably has a greater social and physical impact on us and our planet than anything else we do

On the Activity Privacy of Blockchain for IoT

Security is one of the fundamental challenges in the Internet of Things (IoT) due to the heterogeneity and resource constraints of the IoT devices. Device classification methods are employed to enhance the security of IoT by detecting unregistered devices or traffic patterns. In recent years, blockchain has received tremendous attention as a distributed trustless platform to enhance the security of IoT. Conventional device identification methods are not directly applicable in blockchain-based IoT as network layer packets are not stored in the blockchain. Moreover, the transactions are broadcast and thus have no destination IP address and contain a public key as the user identity, and are stored permanently in blockchain which can be read by any entity in the network. We show that device identification in blockchain introduces privacy risks as the malicious nodes can identify users' activity pattern by analyzing the temporal pattern of their transactions in the blockchain. We study the likelihood of classifying IoT devices by analyzing their information stored in the blockchain, which to the best of our knowledge, is the first work of its kind. We use a smart home as a representative IoT scenario. First, a blockchain is populated according to a real-world smart home traffic dataset. We then apply machine learning algorithms on the data stored in the blockchain to analyze the success rate of device classification, modeling both an informed and a blind attacker. Our results demonstrate success rates over 90\% in classifying devices. We propose three timestamp obfuscation methods, namely combining multiple packets into a single transaction, merging ledgers of multiple devices, and randomly delaying transactions, to reduce the success rate in classifying devices. The proposed timestamp obfuscation methods can reduce the classification success rates to as low as 20%

Error resilience analysis of wireless image transmission using JPEG, JPEG 2000 and JPWL

The wireless extension of the JPEG 2000 standard formally known as JPWL is the newest international standard for still image compression. Different from all previous standards, this new standard was created specifically for wireless imaging applications. This paper examines the error resilience performance of the JPEG, JPEG 2000 and JPWL standards in combating multi-path and fading impairments in Rayleigh fading channels. Comprehensive objective and subjective results are presented in relation to the error resilience performance of these three standards under various conditions. The major findings in this paper reveal that a CRC approach is not a viable option for protecting wireless image data when not used in conjunction with an efficient retransmission strategy. In addition, the Reed-Solomon error correction codes in JPWL provide strong protection for wireless image transmission. However, any stronger protection beyond RS(64,32) yields diminishing returns

Urban agriculture in Botswana

Botswana, a middle-income country, is experiencing a sluggish economic growth and a rapid urbanisation which has brought in its wake high unemployment, poverty and food insecurity. This has led some people to engage in subsistence and commercial urban and peri-urban agriculture (UPA) to address these problems. However, in spite of its known advantages, uptake of UPA has been low for a number of reasons including: high GDP before the economic meltdown of recent years; a harsh climate; lack of water; poor access to land; and over-reliance on generous government handouts. Nevertheless, the extent of its practice and its contribution to food security – albeit modest – shows that it is a sector that needs to be encouraged and supported. Both central and local government can play a big role by providing land and infrastructure, and also by implementing an enabling policy and regulatory environment which promotes small- and medium-scale urban food production