One of the security conditions of Vernam’s cipher is that the encryption key must be greater than or equal to the open text we want to encrypt. At the same time, this key must not be repeated in another encryption. Then, each change of the encryption key adds security to the encryption process. If a cipher is changed several times while encrypting a single open text, it becomes very difficult to decrypt the message. Therefore, our goal is to design a mechanism to generate an encryption key using a Tree Parity Machine and a Genetic Algorithm that will be able to create the same encryption keys on both sides that enter the encryption process. These keys should change during encryption. One of the first tasks is to create an input population for the genetic algorithm from the synchronized Tree parity machine. Therefore, this article presents one of the possible ways to create an input population without using too many synchronizing TPMs.