What is a primary disadvantage of the Caesar cipher?

The primary disadvantage of the Caesar cipher lies in its vulnerability to frequency analysis. This method involves analyzing the frequency of letters in the encrypted message and comparing it to typical letter frequency in the language. Since the Caesar cipher is a substitution cipher that shifts letters by a fixed number, the pattern of letter frequencies remains largely intact. Attackers can utilize the predictability of the cipher to decode messages relatively easily. Once they identify a few common letters, they can deduce the shift used in the cipher, allowing them to break it swiftly.

The complexity of implementation does not present a significant drawback since the Caesar cipher is simple to execute, and while there are a limited number of key combinations (specifically 25 for the English alphabet), this does not constitute a major disadvantage compared to its susceptibility to analysis methods. Additionally, the cipher's restriction to letters does not inherently weaken its security; rather, it defines the scope of its application. Therefore, the ease with which the Caesar cipher can be compromised, particularly through frequency analysis, stands out as its most significant weakness.