The smart city development has been grown faster way, so that such smart cities need requirement that it should be safe, reliable as an infrastructure that can handled the complex system for computations of data in the real time environment. Cryptographic methods make data even safer, more private, and more reliable.  The study discus the blockchain and cryptographic models that used for building smart city which more reliable and resilient to attacks. The proposed approach maintains the stability, efficiency, and longevity of urban systems by emphasizing consensus models, security frameworks, and resiliency indicators.