1# Entropy
2
3Generating cryptographic keys needs a lot of entropy. Especially `gnupg --gen-key`
4depletes the kernel entropy pool (`/dev/random`) quite fast and may appear to be
5stuck when it's waiting for new entropy.
6
7If you wonder how to speed this up consider installing `rng-tools`
8if this is available on your platform.
9
10After installing `rng-tools` please make sure `rngd` is actually running and
11replenishing your entropy pool.
12
13You can do so by keeping a watch on your available entropy and running an entropy
14consuming process as follows:
15
16```bash
17watch -n1 cat /proc/sys/kernel/random/entropy_avail
18# switch to another terminal / screen
19cat /dev/random | rngtest -c 1000
20```
21
22The second command should complete within a few seconds and report no errors.
23If it takes much longer you probably don't have an hardware RNG and will have
24to generate some entropy by triggering some network activity and input.
25
26You should avoid `havaged`.
27
28### Debian / Ubuntu
29
30```bash
31sudo apt-get install rng-tools
32```
33
34### CentOS / Fedora / Red Hat
35
36```bash
37sudo yum install rng-tools
38```
39
40## Further Information
41
42* [RNG-Tools on the Arch Linux Wiki](https://wiki.archlinux.org/index.php/Rng-tools)
43* [gopass Issue #486](https://github.com/gopasspw/gopass/issues/486)
44