With the current fast paced growth in the number of devices connected to the internet, many of these having limited computational capability, security concerns are of increasing importance. To meet the necessity of providing secure encryption to constrained devices many lightweight cryptographic schemes have been developed. This paper provides a comparative study of four of these schemes, namely TEA, XTEA, PRESENT and Simon, explaining how they work and discussing their vulnerabilities and performances. This paper specifically considers the performance of Application Specific Integrated Circuit (ASIC) implementations with regards to their size, throughput, power usage and energy usage per bit encrypted. TEA and PRESENT were found to have potentially problematic vulnerabilities, while no attacks on XTEA and Simon are known that do not reduce the number of rounds used during encryption. Simon and PRESENT were found to perform well, while XTEA implementations were found to be too large for constrained devices. Out of the four, Simon seems the most promising for use in constrained devices. As such, further research into its vulnerabilities is advisable.