The third -party doctrine significantly affects the security of Bitcoin transactions by allowing the police to access negotiation data shared with third -party services, such as cryptocurrency exchange, without entrusting.  

This principle confirms that individuals do not have reasonable expectations for the security of information that is voluntarily shared with third parties. Therefore, when users make transactions through exchanges such as Coinbase, their trading data can be accessed by police without entrusting. This principle also applies to Bitcoin blockchain, evidenced by the United States c. Gratkowski (USA c. Gratkowski, 964 F.3D 307 (5 CIR. 2020)), which is a case at the US appellate court for the fifth circuit regarding the meaning of the fourth Bitcoin transaction amendment. The incident focused on Richard Nikolai Gratkowski, who was charged with being the leader of adolescence content and was the leader of accessing websites with the intention of seeing adolescence content. Evidence against Gratkowski has been taken through a search command based on information collected from the analysis of Bitcoin transactions on the blockchain and customer data of the virtual exchange corner. 

Court rules that blockchain trading files can access the public and are not protected by privacy. This means that the two transactions on the exchange and blockchain can be tested, reducing the overall security and the security of Bitcoin transactions despite its pseudonym. Therefore, third -party doctrine limits the security of Bitcoin transactions, facilitating the monitoring and research of activities related to it.