Feign East, Strike West! Constructing Covert Channel on TLS 1.3

Researchers developed CCCC, a method for hiding secret messages within standard TLS 1.3 connections (the protocol that encrypts web traffic) in a way that appears completely normal to network auditors and censors. The technique uses collision ciphertexts (specially crafted encrypted data that can be decrypted to different messages depending on which secret key is used) and embeds hidden information inside digital signatures, so an eavesdropper with only the public session key sees innocent messages while someone with a pre-shared secret key can extract the hidden communication.