This thesis studies the cryptanalysis and design of some cryptographic algorithms in \emph{symmetric key ciphers}. \emph{Block ciphers} and \emph{Stream ciphers} are two backbone elements in symmetric key ciphers. We cryptanalyze \emph{ZUC} stream cipher, \emph{SERPENT}, \emph{KASUMI} and \emph{SMS4} block ciphers by using some new improved cryptographic methodologies, tools and algorithms. Based on the results obtained in cryptanalysis, we propose some modifications in the designs of \emph{ZUC}, \emph{KASUMI} and \emph{SMS4} to enhance their security. Additionally, we introduce several methodologies to enable and efficiently implement 3-share Threshold Implementation to any 4-bit S-box. Threshold Implementation is widely accepted as a countermeasure against first order Differential Power Analysis in Side Channel Attack and 3-share version is the most efficient in terms of hardware implementation. To support the theoretical results, we construct 3-share Threshold Implementations to S-boxes of \emph{PRESENT}, \emph{SERPENT} ciphers. Notably, 3-share version was believed to be not possible for some S-boxes of \emph{SERPENT} until now.