Enigmail speed geeking
wk at gnupg.org
Sun Mar 15 20:50:01 CET 2015
On Sun, 15 Mar 2015 16:32, stebe at mailbox.org said:
> Now, I'll look for information on how RNG in GnuPG exactly works. It *seems*
> that haveged should impact on the gathering of entropy (available) at the moment
> of keypair generation on any GNU/Linux PC/laptop equipped with it (specific
You can find this in the Libgcrypt manual:
Libgcrypt provides 3 levels or random quality: The level
'GCRY_VERY_STRONG_RANDOM' usually used for key generation, the level
'GCRY_STRONG_RANDOM' for all other strong random requirements and the
function 'gcry_create_nonce' which is used for weaker usages like
nonces. There is also a level 'GCRY_WEAK_RANDOM' which in general maps
to 'GCRY_STRONG_RANDOM' except when used with the function
'gcry_mpi_randomize', where it randomizes an multi-precision-integer
using the 'gcry_create_nonce' function.
There are two distinct random generators available:
* The Continuously Seeded Pseudo Random Number Generator (CSPRNG),
which is based on the classic GnuPG derived big pool
implementation. Implemented in 'random/random-csprng.c' and used
* A FIPS approved ANSI X9.31 PRNG using AES with a 128 bit key.
Implemented in 'random/random-fips.c' and used if Libgcrypt is in
Both generators make use of so-called entropy gathering modules:
Uses the operating system provided '/dev/random' and '/dev/urandom'
Runs several operating system commands to collect entropy from
sources like virtual machine and process statistics. It is a kind
of poor-man's '/dev/random' implementation. It is not available in
Uses the operating system provided Entropy Gathering Daemon (EGD).
The EGD basically uses the same algorithms as rndunix does.
However as a system daemon it keeps on running and thus can serve
several processes requiring entropy input and does not waste
collected entropy if the application does not need all the
collected entropy. It is not available in FIPS mode.
Targeted for the Microsoft Windows OS. It uses certain properties
of that system and is the only gathering module available for that
Extra module to collect additional entropy by utilizing a hardware
random number generator. As of now the only supported hardware RNG
is the Padlock engine of VIA (Centaur) CPUs. It is not available
in FIPS mode.
16.6.1 Description of the CSPRNG
This random number generator is loosely modelled after the one described
in Peter Gutmann's paper: "Software Generation of Practically Strong
A pool of 600 bytes is used and mixed using the core RIPE-MD160 hash
transform function. Several extra features are used to make the robust
against a wide variety of attacks and to protect against failures of
subsystems. The state of the generator may be saved to a file and
initially seed form a file.
Depending on how Libgcrypt was build the generator is able to select
the best working entropy gathering module. It makes use of the slow and
fast collection methods and requires the pool to initially seeded form
the slow gatherer or a seed file. An entropy estimation is used to mix
in enough data from the gather modules before returning the actual
random output. Process fork detection and protection is implemented.
The implementation of the nonce generator (for 'gcry_create_nonce')
is a straightforward repeated hash design: A 28 byte buffer is initially
seeded with the PID and the time in seconds in the first 20 bytes and
with 8 bytes of random taken from the 'GCRY_STRONG_RANDOM' generator.
Random numbers are then created by hashing all the 28 bytes with SHA-1
and saving that again in the first 20 bytes. The hash is also returned
---------- Footnotes ----------
(1) Also described in chapter 6 of his book "Cryptographic Security
Architecture", New York, 2004, ISBN 0-387-95387-6.
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