You might be interested in format transforming encryption then.[0] It is used in tor to prevent deep packet inspection from detecting the initial connection to tor.
Using FTE you can make ciphertext match an arbitrary regex. In the case of tor they are making ciphertext match HTTP traffic.
Using FTE you can make ciphertext match an arbitrary regex. In the case of tor they are making ciphertext match HTTP traffic.
[0] https://kpdyer.com/publications/ccs2013-fte.pdf