Imagine a digital medical history: every record is a block. This entry has a label: the date and time of the entry. Initially, it is considered mandatory to prohibit the modification of records hindsight, because it is necessary that records of diagnosis, treatment, etc. They did not allow different interpretations and remained in the original form. Only a doctor who has one private key and a patient who has another one can access the records. Then, access this information only to those who have one of these users to obtain a private key (for example, the hospital as a whole or a separate specialist). Thus, for example, blocking technology can be used in a medical database.