Ubuntu Manpage: haveged - Generate random numbers and feed linux random device.

NAME

       haveged - Generate random numbers and feed linux random device.

SYNOPSIS

       haveged [options]

DESCRIPTION

The HAVEGE (HArdware Volatile Entropy Gathering and Expansion) algorithm harvests the
indirect effects of hardware events on hidden processor state (caches, branch predictors,
memory translation tables, etc) to generate a random sequence. The effects of interrupt
service on processor state are visible from user land as timing variations in program
execution speed. Using a branch-rich calculation that fills the processor instruction and
data cache, a high resolution timer source such as the processor time stamp counter can
generate a random sequence even on an "idle" system.

In Linux, the hardware events that are the ultimate source of any random number sequence
are pooled for distribution by the /dev/random and /dev/urandom device interface. The
standard mechanism of harvesting randomness for the pool may not be sufficient to meet
demand, especially on those systems with high needs or limited user interaction. Haveged
provides a daemon to fill /dev/random whenever the supply of random bits in /dev/random
falls below the low water mark of the device.

Haveged also provides a direct file system interface to the collection mechanism that is
also useful in other circumstances where access to the dev/random interface is either not
available or inappropriate.

The size of the processor level 1 instruction and data caches are used to tune the HAVEGE
algorithm for maximum sensitivity. The sizes of these caches may be input directly on the
command line. For sizes not specified, haveged will attempt to determine the sizes
dynamically from the Linux sysfs and/or cpuid instruction with a fallback to a compiled
default (usually 16k) if better information is not available.

Haveged includes a run time test facility based upon the test suite defined in the AIS-31
specification from the The German Federal Office for Information Security (Bundesamt für
Sicherheit in der Informationstechnik). The test suite consists of 9 statistical tests
packaged into two test suites ("A" and "B"). The tests can be run at initialization
(a.k.a. a "tot" test), or continuously to monitor all output. Failure of a suite will
terminate execution unless explicitly waived in the onlinetest command line option.

Procedure A contains 6 test procedures. The first test, 'test0', is run once. This is
followed by 257 repetitions of the FIPS140-1 tests, 'test1' through 'test4', and an auto-
correlation test, 'test5'. The fixed size of the Procedure A input makes it ideal for
continuous use but test5 is several orders of magnitude slower than any other individual
AIS test. As an alternative for those who cannot tolerate this load, procedure A variants
A<n> are provided that execute all included tests but executes test5 only every 2^n
repetitions.

Procedure B contains 3 tests, 'test6', 'test7', 'test8'. Because first two tests check the
distribution of disjoint bit sequences, the input size for the test is variable. The last
test provides an entropy estimate of the input which makes this test well suited to the
haveged daemon role.

Each test procedure requires more than 1MB of data. In those cases where a continuous test
procedure cannot be completed in the available buffer space (see --buffer), the complete
buffer will be discarded on a single failed individual test and a refill initiated to
resolve the outcome of the built in retry before additional data becomes available.

OPTIONS

-b nnn, --buffer=nnn
Set collection buffer size to nnn KW. Default is 128KW (or 512KB).

-d nnn, --data=nnn
Set data cache size to nnn KB. Default is 16 or as determined dynamically.

-f file, --file=file
Set output file path for non-daemon use. Default is "sample", use '-' for stdout.

-F , --Foreground
Run daemon in foreground. Do not fork and detach, use '-' for stdout.

-i nnn, --inst=nnn
Set instruction cache size to nnn KB. Default is 16 or as determined dynamically.

-n nnn, --number=nnn
Set number of bytes written to the output file. The value may be specified using
one of the suffixes k, m, g, or t. The upper bound of this value is "16t" (2^44
Bytes = 16TB). A value of 0 indicates unbounded output and forces output to
stdout.

-o <spec>, --onlinetest=<spec>
Specify online tests to run. The <spec> consists of optional 't'ot and 'c'ontinuous
groups, each group indicates the procedures to be run, using "a<n>" to indicate a
AIS-31 procedure A variant, and "b" to indicate AIS procedure B. The specifications
are order independent (procedure B always runs first) and case insensitive. A "w"
can be appended to any test token to make the test advisory only. The default is
"ta8bcb" if run as a daemon and "ta8b" otherwise.

For example, the string "tbca8b" is suitable for an AIS NTG.1 device (use procedure
B for the "tot" test, then cycle between procedure A8 and procedure B continuously
for all further output). The default is "tb". Resources are allocated only for
tests used, in minimal resource situations, "tc" can be used to disable all testing
and avoid all test resource allocations.

-p file, --pidfile=file
Set file path for the daemon pid file. Default is "/var/run/haveged.pid",

-r n, --run=n
Set run level for daemon interface:

n = 0 Run as daemon - must be root. Fills /dev/random when the supply of random
bits
falls below the low water mark of the device. This argument is required if the
daemon interface is not present. If the daemon interface is present, this takes
precedence over any -r value.

n = 1 Display configuration info and terminate.

n > 1 Write <n> kb of output. Deprecated (use -n instead), only provided for
backward compatibility.

-v n, --verbose=n
Set output level 0=minimal, 1=config/fill items, use -1 for all diagnostics.

-w nnn, --write=nnn
Set write_wakeup_threshold of daemon interface to nnn bits. Applies only to run
level 0.

-?, --help
This summary of program options.

DIAGNOSTICS

       The following diagnostics may be issued to stderr upon termination:

       Cannot fork into the background
              Call to daemon(3) failed.

       Cannot open file <s> for writing.
              Could not open sample file <s> for writing.

       Cannot write data in file:
              Could not write data to the sample file.

       Couldn't get poolsize.
              Unable to read /proc/sys/kernel/random/poolsize

       Couldn't initialize HAVEGE rng
              Invalid data or instruction cache size.

       Couldn't open PID file <s> for writing
              Unable to write daemon PID

       Couldn't open random device
              Could not open /dev/random for read-write.

       Couldn't query entropy-level from kernel: error
              Call to ioctl(2) failed.

       Couldn't open PID file <path> for writing
              Error writing /var/run/haveged.pid

       Fail:set_watermark()
              Unable to write to /proc/sys/kernel/random/write_wakeup_threshold

       RNDADDENTROPY failed!
              Call to ioctl(2) to add entropy failed

       RNG failed
              The random number generator failed self-test or encountered a fatal error.

       Select error
              Call to select(2) failed.

       Stopping due to signal
              Signal caught

       Unable to setup online tests
              Memory unavailable for online test resources.

EXAMPLES

       Write 1.5MB of random data to the file /tmp/random
              haveged -n 1.5M -f /tmp/random

       Generate a /tmp/keyfile for disk encryption with LUKS
              haveged -n 2048 -f /tmp/keyfile

       Overwrite partition /dev/sda1 with random data. Be careful, all data on the partition will
       be lost!
              haveged -n 0 | dd of=/dev/sda1

       Generate random ASCII passwords of the length 16 characters
              (haveged  -n  1000  -f  - 2>/dev/null | tr -cd '[:graph:]' | fold -w 16 && echo ) |
              head

       Write endless stream of random bytes to the pipe. Utility pv measures the speed  by  which
       data are written to the pipe.
              haveged -n 0 | pv > /dev/null

       Evaluate speed of haveged to generate 1GB of random data
              haveged -n 1g -f - | dd of=/dev/null

       Create a random key file containing 65 random keys for the encryption program aespipe.
              haveged -n 3705 -f - 2>/dev/null | uuencode -m - | head -n 66 | tail -n 65

       Test the randomness of the generated data with dieharder test suite
              haveged -n 0 | dieharder -g 200 -a

       Generate  16k  of  data, testing with procedure A and B with detailed test results. Note c
       test never completes
              haveged -n 16k -o tba8ca8 -v 33

       Generate 16k of data as above with larger buffer. Note c test completion
              haveged -n 16k -o tba8ca8 -v 33 -b 256

       Generate 16m of data as above, Note c test completions with default buffer size.
              haveged -n 16m -o tba8ca8 -v 33

References

       HArdware Volatile Entropy Gathering and Expansion: generating unpredictable random numbers
       at user level by A. Seznec, N. Sendrier, INRIA Research Report, RR-4592, October 2002

       A  proposal  for: Functionality classes for random number generators by W. Killmann and W.
       Schindler, version  2.0,  Bundesamt  fur  Sicherheit  in  der  Informationstechnik  (BSI),
       September, 2011

       A  Statistical  Test Suite for the Validation of Random NUmber Generators and Pseudorandom
       Number Generators for Cryptographic Applications, special publication  SP800-22,  National
       Institute of Standards and Technology, revised April, 2010

AUTHOR

       Gary Wuertz <gary@issiweb.com> and Jirka Hladky <hladky jiri AT gmail DOT com>

REFERENCES

       http://www.issihosts/haveged/