>That is very convenient, since it's easy to detect when people are communicating on a secure channel. This is a fairly complicated question. Disk/file encrypt

>That is very convenient, since it's easy to detect when people are communicating on a secure channel. This is a fairly complicated question. Disk/file encryption is not easy to detect without access to the disk , however I won't discuss that here because you only addressed communication. Generally when policy people talk about encryption they mean technologies which protect confidentiality, but not technologies which protect authentication e.g. signature algorithms, MACs, etc. Authentication technologies often contain random fields such as nonces this provides a very obvious location to store encrypted data in a message. Given that ciphertexts should be indistinguishable from randomness, an attacker should not be able to tell that a random field is not random without the key. There are already tools which hide ciphertexts in nonce fields. Compression also provides a useful place to hide ciphertexts since it looks random as well. Most criminals will not go to the lengths above. Most people including most criminals prefer convenience over security. That being said, if communication security is important to a crime (and it usually isn't), and the criminals are competent at INFOSEC (they usually aren't) they can and will use encryption which is not easily detectable (spies can and will use hard to detect encryption even if encryption is illegal). We are moving toward a society in which almost anything done in public is recorded and analyzed via video, RFID/cell tower access patterns/social media/license plate readers. Police have never had more tools to investigate crime and never had more evidence to convict people. If LEOs so wished and had the resources to handle the caseload and arrests they could get ~90% clearance for jaywalking.