srandom is a Linux kernel module that can be used like the built-in /dev/urandom & /dev/random device files. In the standard mode (ChaCha8) it is about 20%-40% faster than built-in urandom and should be secure enough for crypto. In ultra high speed mode it is about 500% faster (5x faster) than the built-in urandom generator. YMWV depending on hardware and software configuration. It should compile and install on any Linux 3.17+ kernel. Both ChaCha8 and (UHS)XorShift pass all the randomness tests using dieharder.
srandom was created as a performance improvement to the built-in PRNG /dev/urandom number generator. I wanted a much faster random number generator to wipe ssd disks. The UHS algorithm is many times faster than urandom, but still produces excellent random numbers that dieharder finds indistinguishable from true random numbers. You can easily wipe multiple SSDs at the same time.
The built-in PRNG generators (/dev/random and /dev/urandom) uses Chacha20 and are technically not flawed. They are just very slow when compared to srandom. /dev/random and /dev/urandom are BOTH PRNG generators.
Truth is, when state-of-the-art hash algorithms are broken, or when state-of-the-art block ciphers are broken, it doesn't matter that you get “philosophically insecure” random numbers because of them. You've got nothing left to securely use them for anyway.
What makes srandom a great PRNG generator?
- Higher speed vs the built-in random devices.
- It's configurable to use ChaCha8 or UHS(XorShift) depending on your use-case.
- ChaCha8 and UHS both pass Dieharder tests.
- Plug and play.
-
Use standard mode (ChaCha8) for any security type applications that rely heavily on random numbers. For example, Apache SSL (Secure Socket Level), PGP (Pretty Good Privacy), VPN (Virtual Private Networks). All types of Encryption, Password seeds, Tokens would rely on a source of random numbers. There is many examples at https://www.random.org/testimonials/.
-
Use UHS for disk wiping or any application that does not involve crypto, or if you're not overly concerned about random numbers affecting security.
To build & compile the kernel module. A pre-req is "kernel-devel". Use yum or apt to install.
make
To load the kernel module into the running kernel (temporary).
make load
To unload the kernel module from the running kernel.
make unload
To install the kernel module on your system (persistent on reboot).
make install ; make load
To uninstall the kernel module from your system.
make uninstall
This mode uses the two 64bit XorShift PRNGs. This mode performs much faster than ChaCha8, but still passes dieharder tests. To enable this mode, set the following line in the source code before running make.
#define ULTRA_HIGH_SPEED_MODE 1
You can load the kernel module temporary, or you can install the kernel module to be persistent on reboot.
- If you want to just test the kernel module, you should run "make load". This will load the kernel module into the running kernel and create a /dev/srandom accessible to root only. It can be removed with "make unload". You can monitor the load process in /var/log/messages.
- When you run "make install", the srandom kernel module is moved to /usr/lib/modules/.../kernel/drivers/. If you run "make load" or reboot, the kernel module will be loaded into the running kernel, but now will replace the /dev/urandom device file. The old /dev/urandom device is renamed (keeping it's inode number). This allows any running process that had /dev/urandom to continue running without issues. All new requests for /dev/urandom will use the srandom kernel module.
- Once the kernel module is loaded, you can access the module information through the /proc filesystem. For example:
# cat /proc/srandom
-----------------------:----------------------
Device : /dev/srandom
Module version : 2.0.0 UHS (XorShift)
Current open count : 3
Total open count : 42
Total K bytes : 38030518
-----------------------:----------------------
Author : Jonathan Senkerik
Website : https://www.jintegrate.co
github : https://github.com/josenk/srandom
- Use the /usr/bin/srandom tool to set srandom as the system PRNG, set the system back to default PRNG, or get the status.
# /usr/bin/srandom help
# /usr/bin/srandom status
Module loaded
srandom if functioning correctly
/dev/urandom is LINKED to /dev/srandom (system is using srandom)
- To completely remove the srandom module, use "make uninstall". Depending if there is processes accessing /dev/srandom, you may not be able to remove the module from the running kernel. Try "make unload", if the module is busy, then a reboot is required.
A simple dd command to read from the /dev/srandom device will show performance of the generator. The results below are typical from my system. Of course, your performance will vary.
The "UHS" srandom number generator
time dd if=/dev/srandom of=/dev/null count=64k bs=64k
65536+0 records in
65536+0 records out
4294967296 bytes (4.3 GB, 4.0 GiB) copied, 1.88435 s, 2.3 GB/s
real 0m1.886s
user 0m0.004s
sys 0m1.866s
The built-in urandom number generator
time dd if=/dev/urandom of=/dev/null count=64k bs=64k
65536+0 records in
65536+0 records out
4294967296 bytes (4.3 GB, 4.0 GiB) copied, 9.75787 s, 440 MB/s
real 0m9.760s
user 0m0.015s
sys 0m9.680s
The most important part of the random number device file is that is produces random/unpredictable numbers. The golden standard of testing randomness is the dieharder test suite (http://www.phy.duke.edu/~rgb/General/dieharder.php). The dieharder tool will easily detect flawed random number generators. After you install dieharder, use the following command to put /dev/srandom through the battery of tests.
A note about the possibility of a test showing as "WEAK"... If a test is repeatedly "FAILED" or "WEAK", then that is a problem.
dd if=/dev/srandom |dieharder -g 200 -f - -a
#=============================================================================#
# dieharder version 3.31.1 Copyright 2003 Robert G. Brown #
#=============================================================================#
rng_name | filename |rands/second|
stdin_input_raw| -| 5.85e+07 |
#=============================================================================#
test_name |ntup| tsamples |psamples| p-value |Assessment
#=============================================================================#
diehard_birthdays| 0| 100| 100|0.81047982| PASSED
diehard_operm5| 0| 1000000| 100|0.05511543| PASSED
diehard_rank_32x32| 0| 40000| 100|0.01261989| PASSED
diehard_rank_6x8| 0| 100000| 100|0.47316309| PASSED
diehard_bitstream| 0| 2097152| 100|0.74346434| PASSED
diehard_opso| 0| 2097152| 100|0.98820557| PASSED
diehard_oqso| 0| 2097152| 100|0.38452940| PASSED
diehard_dna| 0| 2097152| 100|0.23079735| PASSED
diehard_count_1s_str| 0| 256000| 100|0.35819763| PASSED
diehard_count_1s_byt| 0| 256000| 100|0.18753110| PASSED
diehard_parking_lot| 0| 12000| 100|0.29327315| PASSED
diehard_2dsphere| 2| 8000| 100|0.35160725| PASSED
diehard_3dsphere| 3| 4000| 100|0.49118105| PASSED
diehard_squeeze| 0| 100000| 100|0.33775434| PASSED
diehard_sums| 0| 100| 100|0.37711818| PASSED
diehard_runs| 0| 100000| 100|0.54179533| PASSED
diehard_runs| 0| 100000| 100|0.73976903| PASSED
diehard_craps| 0| 200000| 100|0.66525469| PASSED
diehard_craps| 0| 200000| 100|0.84537370| PASSED
marsaglia_tsang_gcd| 0| 10000000| 100|0.10708190| PASSED
marsaglia_tsang_gcd| 0| 10000000| 100|0.87071126| PASSED
sts_monobit| 1| 100000| 100|0.30011393| PASSED
sts_runs| 2| 100000| 100|0.91175959| PASSED
<<< etc... >>>
If you installed the kernel module to load on reboot, then you do not need to modify any applications to use the srandom kernel module. It will be linked to /dev/urandom, so all applications will use it automatically. However, if you do not want to link /dev/srandom to /dev/urandom, then you can configure your applications to use which ever device you want. Here is a few examples....
Java: Use the following command line argument to tell Java to use the new random device
-Djava.security.egd=file:///dev/srandom switch
or
-Djava.security.egd=file:/dev/./srandom
Java: To make the setting as default, add the following line to the configuration file. ($JAVA_HOME/jre/lib/security/java.security)
securerandom.source=file:/dev/./srandom
https: (Apache SSL), Configure /etc/httpd/conf.d/ssl.conf
SSLRandomSeed startup file:/dev/srandom 512
SSLRandomSeed connect file:/dev/srandom 512
Postfix: Change the following line in /etc/postfix/main.cf
tls_random_source = dev:/dev/srandom
PHP: Change the following line in PHP config file.
session.entropy_file = /dev/srandom
OpenLDAP: Change the following line in /etc/openldap/slapd.conf
TLSRandFile /dev/srandom
*** This will DESTROY DATA! Use with caution! ***
*** Replace /dev/sdXX with your disk device you want to wipe.
dd if=/dev/srandom of=/dev/sdXX bs=64k
Copyright (C) 2019 Jonathan Senkerik
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.