Is Dev urandom secure?
There is also the Random package which uses the ISAAC algorithm; which is considered secure. These aren’t bad solutions, but if you are in a modern Linux based environment your kernel should have support for /dev/random and /dev/urandom.
Does urandom block?
/dev/urandom will never block. In rare cases very shortly after boot, the CSPRNG may not have had enough entropy to be properly seeded and /dev/urandom may not produce high-quality randomness.
What is cat Dev urandom?
/dev/urandom is a continuous stream of random data. It will never produce an end of file. Buffered reads will fill the read buffer, so even if you are piping the output of cat into some other program, the read won’t be terminated until the pipe is closed.
What happens if you try to write to Dev null and Dev Zero?
1 Answer. Yes, both accept and discard all input, but their output is not the same: /dev/null produces no output. /dev/zero produces a continuous stream of NULL (zero value) bytes.
What is Dev null used for?
The null device is typically used for disposing of unwanted output streams of a process, or as a convenient empty file for input streams. This is usually done by redirection. The /dev/null device is a special file, not a directory, so one cannot move a whole file or directory into it with the Unix mv command.
Can you get better randomness than / dev / urandom?
The long answer is also yes. /dev/urandom yields data which is indistinguishable from true randomness, given existing technology. Getting “better” randomness than what /dev/urandom provides is meaningless, unless you are using one of the few “information theoretic” cryptographic algorithm, which is not your case (you would know it).
Do you need to read from urandom before reading from random?
In NetBSD, you’d want to read from /dev/random at least once before reading from /dev/urandom to ensure it has been seeded properly. On FreeBSD and MacOS there is no difference between /dev/random and /dev/urandom. The short answer is still to use /dev/urandom.
How does randomness work in a virtual machine?
/dev/random: very high quality of randomness, extracted directly from the entropy pool (itself fed mostly by peripherals interrupts timings and block devices seek times); it will block if you request more bits than available in the entropy pool (as reported by cat /proc/sys/kernel/random/entropy_avail)
How to use VirtIO RNG on a virtual machine?
Using the QEMU/KVM VirtIO RNG device, you can make the physical, entropy-rich, hypervisor emulate a hardware RNG and pass it to the VM, where it will appear as a /dev/hwrng. Recent versions of the Linux kernel will automatically detect and use this hardware device, as reported by cat /sys/devices/virtual/misc/hw_random/rng_available => virtio_rng .