This weekend I am not going back in time to fundamentals, but looking forward to the future. Encryption techniques to protect sensitive information such as personal identifiable information are becoming more and more practical, and ubiquitously. Whether in-the-cloud or on-premise there is a shift to a model where individual applications need to protect themselves instead of relying on firewall-like techniques. That goes especially for the interaction between applications and storage engines, and between applications and databases. In last year's SOSP Hari Balakrishnan's group at MIT CSAIL team presented a paper on CryptDB which has a novel SQL-aware encryption approach.
"CryptDB: Protecting Confidentiality with Encrypted Query Processing", Raluca Ada Popa and Catherine Redfield and Nickolai Zeldovich and Hari Balakrishnan,Symposium on Operating Systems Principles Cascais, Portugal, October 2011
You can download the CryptDB software from here