Universal composability (UC) framework is a method for design and analysis of provable secure cryptoprotocols and it was introduced by Ran Canetti in 2001. Although the framework provides strong theoretical background, and several protocol analysis appears in the literature, the most usual case is the security analysis of protocols that already designed according to the UC framework. In contrast, practical analysis of already existing cryptographic protocols can be rarely find in the literature. In this work our aim is to propose an UC-based practical method for the security analysis of cryptographic protocols, where the protocol was not designed along UC-techniques, rather by traditional practical techniques. The main attractive feature of the UC approach is modular analysis. Our first modularization step is carried out along appropriate idealization of communication channels between parties of the protocol instance. We only describe the method for lower layer tasks, and we also give some example protocol to demonstrate the method.