How to speed up OpenSSL/GnuPG Entropy For Random Number Generation On Linux

Posted on in Categories Howto, Open Source, Security last updated November 7, 2016

Entropy is nothing but the measure of “randomness” in a sequence of bits. The PRNG ( pseudorandom number generator ) is a special device (e.g. /dev/random on Linux) to create randomness from server hardware activities. It uses interrupts generated from the keyboard, hard disk, mouse, network and other sources. The random number generator gathers environmental noise from device drivers and other sources into an entropy pool. The randomness usually used for security purposes like creating TLS/SSL keys and the quality source of random bits is critical. For example, OpenSSL APIs can use quality randomness to make your program cryptographically secure. However, a poor source of randomness could result in loss of security. In this post, I will cover haveged and rng-utils/rng-tools to generate random numbers and feed linux random device for your virtual or dedicated Linux server.

Running out of entropy on server or VMs is common

To see available entropy on Linux, enter:
$ cat /proc/sys/kernel/random/entropy_avail
Sample outputs:

378

It is rather low (anything below =< 1000) is going to take a long time to generate randomness using /dev/random as apps will block until you have enough entropy. In other words, you will see slow speed while generating keys or while using OpenSSL APIs. I recently asked on Twitter about it:


I was suggested to look into the haveged project. The haveged software provides an easy-to-use, unpredictable random number generator based on an adaptation of the HAVEGE algorithm. Another suggested option was to use rng-tools/rng-utils to speed up entropy.

Finding out your current availability of entropy and quality of randomness

You need to use the rngtest command as follows. Install it from rng-tools without starting rng in background:
$ sudo RUNLEVEL=1 apt-get install rng-tools
$ cat /dev/random | rngtest -c 1000

It is going to take forever to run last command due to low quality randomness. Let us see how to install haveged or rng-tools.

Option #1: Install haveged

Linux entropy source using the HAVEGE algorithm and can installed as follows:

Debian/Ubuntu Linux

Type the following apt-get command:
$ sudo apt-get install haveged
Sample outputs:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  libhavege1
The following NEW packages will be installed:
  haveged libhavege1
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Need to get 49.8 kB of archives.
After this operation, 196 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://01.archive.ubuntu.com/ubuntu xenial/universe amd64 libhavege1 amd64 1.9.1-3 [21.8 kB]
Get:2 http://01.archive.ubuntu.com/ubuntu xenial/universe amd64 haveged amd64 1.9.1-3 [28.0 kB]
Fetched 49.8 kB in 0s (58.6 kB/s)  
Selecting previously unselected package libhavege1:amd64.
(Reading database ... 233574 files and directories currently installed.)
Preparing to unpack .../libhavege1_1.9.1-3_amd64.deb ...
Unpacking libhavege1:amd64 (1.9.1-3) ...
Selecting previously unselected package haveged.
Preparing to unpack .../haveged_1.9.1-3_amd64.deb ...
Unpacking haveged (1.9.1-3) ...
Processing triggers for libc-bin (2.23-0ubuntu4) ...
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for systemd (229-4ubuntu12) ...
Processing triggers for ureadahead (0.100.0-19) ...
ureadahead will be reprofiled on next reboot
Setting up libhavege1:amd64 (1.9.1-3) ...
Setting up haveged (1.9.1-3) ...
Processing triggers for libc-bin (2.23-0ubuntu4) ...
Processing triggers for systemd (229-4ubuntu12) ...
Processing triggers for ureadahead (0.100.0-19) ...

RHEL/CentOS Linux

First, turn on EPEL repo and type:
$ sudo yum install epel-release
$ sudo yum install haveged

Sample outputs:

Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: centos.excellmedia.net
 * epel: epel.mirror.angkasa.id
 * extras: centos.excellmedia.net
 * updates: centos.excellmedia.net
Resolving Dependencies
--> Running transaction check
---> Package haveged.x86_64 0:1.9.1-1.el7 will be installed
--> Finished Dependency Resolution
 
Dependencies Resolved
 
=================================================================================
 Package           Arch             Version                 Repository      Size
=================================================================================
Installing:
 haveged           x86_64           1.9.1-1.el7             epel            61 k
 
Transaction Summary
=================================================================================
Install  1 Package
 
Total download size: 61 k
Installed size: 181 k
Is this ok [y/d/N]: y
Downloading packages:
warning: /var/cache/yum/x86_64/7/epel/packages/haveged-1.9.1-1.el7.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID 352c64e5: NOKEY
Public key for haveged-1.9.1-1.el7.x86_64.rpm is not installed
haveged-1.9.1-1.el7.x86_64.rpm                            |  61 kB  00:00:00     
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
Importing GPG key 0x352C64E5:
 Userid     : "Fedora EPEL (7) <[email protected]>"
 Fingerprint: 91e9 7d7c 4a5e 96f1 7f3e 888f 6a2f aea2 352c 64e5
 Package    : epel-release-7-6.noarch (@extras)
 From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
Is this ok [y/N]: y
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : haveged-1.9.1-1.el7.x86_64                                    1/1 
  Verifying  : haveged-1.9.1-1.el7.x86_64                                    1/1 
 
Installed:
  haveged.x86_64 0:1.9.1-1.el7                                                   
 
Complete!

That is all. Test it:
$ cat /proc/sys/kernel/random/entropy_avail
$ cat /dev/random | rngtest -c 1000
$ haveged -n 2g -f - | dd of=/dev/null

Option #2: Install rng-utils/rng-tools

The rngd is hardware RNG entropy gatherer daemon. Type the following yum command on a CentOS/RHEL based system:
$ sudo yum install -y rng-utils
Sample outputs:

Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: centos.excellmedia.net
 * epel: epel.mirror.angkasa.id
 * extras: centos.excellmedia.net
 * updates: centos.excellmedia.net
Resolving Dependencies
--> Running transaction check
---> Package rng-tools.x86_64 0:5-7.el7 will be installed
--> Finished Dependency Resolution
 
Dependencies Resolved
 
=========================================================================
 Package            Arch            Version          Repository     Size
=========================================================================
Installing:
 rng-tools          x86_64          5-7.el7          base           34 k
 
Transaction Summary
=========================================================================
Install  1 Package
 
Total download size: 34 k
Installed size: 68 k
Is this ok [y/d/N]: y
Downloading packages:
rng-tools-5-7.el7.x86_64.rpm                        |  34 kB   00:00     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : rng-tools-5-7.el7.x86_64                              1/1 
  Verifying  : rng-tools-5-7.el7.x86_64                              1/1 
 
Installed:
  rng-tools.x86_64 0:5-7.el7                                             
 
Complete!

Debian / Ubuntu Linux users type the following apt-get command:
$ sudo apt-get install rng-tools
Sample outputs:

[sudo] password for vivek: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
  rng-tools
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 21.9 kB of archives.
After this operation, 139 kB of additional disk space will be used.
Get:1 http://01.archive.ubuntu.com/ubuntu xenial/universe amd64 rng-tools amd64 5-0ubuntu3 [21.9 kB]
Fetched 21.9 kB in 0s (34.3 kB/s)    
Selecting previously unselected package rng-tools.
(Reading database ... 233574 files and directories currently installed.)
Preparing to unpack .../rng-tools_5-0ubuntu3_amd64.deb ...
Unpacking rng-tools (5-0ubuntu3) ...
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for systemd (229-4ubuntu12) ...
Processing triggers for ureadahead (0.100.0-19) ...
ureadahead will be reprofiled on next reboot
Setting up rng-tools (5-0ubuntu3) ...
Processing triggers for systemd (229-4ubuntu12) ...
Processing triggers for ureadahead (0.100.0-19) ...

That is all. Test it:
$ cat /proc/sys/kernel/random/entropy_avail
$ cat /dev/random | rngtest -c 1000

Fig.01: Testing availability of entropy & quality of randomness on Linux
Fig.01: Testing availability of entropy & quality of randomness on Linux

Examples

To generate a strong DH group or GPG keys using CLI, run:
Now you should see speed up while using the following commands. To use perfect forward secrecy cipher suites, you must set up Diffie-Hellman parameters on the server side:
$ openssl dhparam -out dhparams.pem 2048
OR
$ openssl dhparam -out dhparams.pem 4096
OR
$ openssl dhparam -out dhparams.pem -dsaparam 4096
Type the following command to generates a key pair that consists of a public and a private key, execute:
$ gpg2 --gen-key
To generate a /root/keyfile for disk encryption with LUKS, enter:
$ sudo haveged -n 2048 -f /root/keyfile
To generate random ASCII passwords of the length 16 characters, run:
$ (haveged -n 1000 -f - 2>/dev/null | tr -cd '[:graph:]' | fold -w 16 && echo ) | head -1
To test the randomness of the generated data with dieharder test suite (use ‘apt-get install dieharder‘ to use dieharder on Debian/Ubuntu Linux):
$ haveged -n 0 | dieharder -g 200 -a
Sample outputs:

Writing unlimited bytes to stdout
#=============================================================================#
#            dieharder version 3.31.1 Copyright 2003 Robert G. Brown          #
#=============================================================================#
   rng_name    |rands/second|   Seed   |
stdin_input_raw|  2.22e+07  |2467094284|
#=============================================================================#
        test_name   |ntup| tsamples |psamples|  p-value |Assessment
#=============================================================================#
   diehard_birthdays|   0|       100|     100|0.57766651|  PASSED  
      diehard_operm5|   0|   1000000|     100|0.18806468|  PASSED  
  diehard_rank_32x32|   0|     40000|     100|0.94961511|  PASSED  
    diehard_rank_6x8|   0|    100000|     100|0.89699673|  PASSED  
   diehard_bitstream|   0|   2097152|     100|0.01373793|  PASSED  
        diehard_opso|   0|   2097152|     100|0.33382051|  PASSED  
        diehard_oqso|   0|   2097152|     100|0.59662327|  PASSED  
         diehard_dna|   0|   2097152|     100|0.18392060|  PASSED  
diehard_count_1s_str|   0|    256000|     100|0.35838284|  PASSED  
diehard_count_1s_byt|   0|    256000|     100|0.93169702|  PASSED  
 diehard_parking_lot|   0|     12000|     100|0.25432384|  PASSED  
    diehard_2dsphere|   2|      8000|     100|0.19976795|  PASSED  
    diehard_3dsphere|   3|      4000|     100|0.72109364|  PASSED  
     diehard_squeeze|   0|    100000|     100|0.70961203|  PASSED  
...
..
....

A note about ChaosKey

There is a hardware based True Random Number Generator that attaches via USB:

Chaoskey v 3.0
Chaoskey v 3.0

References:

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

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