This research investigates the problem of reward distribution in social networks to increase the effectiveness of crowdsourcing tasks for sponsors. Our goal is to design reward mechanisms that encourage early adopters to actively recruit more contributors, thereby streamlining task completion. However, participants may resort to strategic manoeuvres such as withholding invitations, exaggerating their task skills, or fabricating identities (Sybil attacks) to maximize personal gains. To address this dilemma, we introduce a novel mechanism, called the Propagation Reward Distribution Mechanism (PRDM), which effectively motivates agents to exert maximum effort, disseminate tasks throughout their social networks, and discourages Sybil attacks.