It's more like the parts that have to be secret should be small and easily changed (passwords, keys, etc.) rather than your protocols (which are going to be ver

It's more like the parts that have to be secret should be small and easily changed (passwords, keys, etc.) rather than your protocols (which are going to be very hard to change). There's no harm in a layer of obscurity over a secure system, but there's a social problem where it's more often used to obscure the workings of insecure systems than anything else. So all things being equal, one would prefer the cipher that's been well-studied by academics without being broken vs. the mystery cipher that claims to use all the most secure cryptographic constructs without giving anyone the details.