Dear Readers,
 
 It is the great honor for us to publish seventh volume, second issue of Contemporary Educational Researches Journal.
 Journal welcomes original empirical investigations and comprehensive literature review articles focusing on educational issues. The journal an international peer-refereed that promotes researches in field contemporary teaching learning approaches ...

We put forward a new model for understanding the security of symmetric-key primitives, such as block ciphers. The model captures the fact that many such primitives often consist of iterating simpler constructs for a number of rounds, and may provide insight into the security of such designs. We completely characterize the security of four-round Luby-Rackoff ciphers in our model, and show that t...