Secure Message of Integers

Alice wants to send a secret message to Bob over an insecure channel by encrypting it so that no hacker can eavesdrop. $\underline{\textbf{Assumptions:}}$ - $P$ is the plaintext which represents the original message and consists of $m$ 8-bit unsigned integer numbers separated by one whitespace, i.e., $P$ = $\{n_0 n_1 n_2 n_3 \cdots n_{m-1}\}$ where each $n_i$ is an 8-bit unsigned integer number.