As computing becomes pervasive, embedded systems are deployed in a wide range of domains, including industrial systems, critical infrastructures, private and public spaces as well as portable and wearable applications. An integral part of the functionality of these systems is the storage, access and transmission of private, sensitive or even critical information. Therefore, the confidentiality and integrity of the resources and services of said devices constitutes a prominent issue that must be considered during their design. There is a variety of cryptographic mechanisms which can be used to safeguard the confidentiality and integrity of stored and transmitted information. In the context of embedded systems, however, the problem at hand is exacerbated by the resource-constrained nature of the devices, in conjunction with the persistent need for smaller size and lower production costs. This paper provides a comparative analysis of lightweight cryptographic algorithms applicable to such devices, presenting recent advances in the field for symmetric and asymmetric algorithms as well as hash functions. A classification and evaluation of the schemes is also provided, utilizing relevant metrics in order to assess their suitability for various types of embedded systems.