Cipher
How could we ever know that we have a “good” cipher, or how “good” it is?
There is no way to measure strength for an arbitrary practical cipher.
Theoretical strength “proofs” almost never apply in practice.
Nobody “on our side” can know that our ciphers are “good,” no matter how well-educated, experienced or smart they are, because that is determined by adversaries in secret.
Conventional cryptography often instils belief in “known” cipher strength, ignoring logic and lessons learned while a state of metanoia plays into the hands of potential adversaries. A healthy dose of paranoia without landing ourselves in a state of (over)protectionism is required.