# Mono-alphabetic substitution **Mono-alphabetic substitution** is a simple substitution cipher where **each letter of the plaintext is substituted with a fixed corresponding letter** of the ciphertext, based on a single shared alphabet or a key. It is considered to be easily broken due to the lack of complexity in the substitution process and the predictability of letter frequency patterns in the language used. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://www.ctfrecipes.com/cryptography/mono-alphabetic-substitution.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.