It is my understanding that the raw output from
non-blocking /dev/random (where the kernel's entropy_avail estimate is equal to or greater than the number of random bits required)
- or properly-initialized /dev/urandom (i.e., after roughly 256 bits of entropy have been collected by the system)
can be used without further post-processing as strong keymat for long-term symmetric crypto keys.
The output is gathered thusly (for the symmetric key):
//output 256 bits of entropy in 64 hex digits od -N 64 -x /dev/random
Is there any weakness in this method as I have been recently led to believe (with no justification other than 'it's common knowledge', supposedly), or is raw /dev/[u]random output usable for long-term (>10 year) keymat?
Edit: remove any reference to asymmetric crypto to make its own question.