MCOOKIE(1) Linux Programmer's Manual MCOOKIE(1)NAME
mcookie - generate magic cookies for xauth
SYNOPSIS
mcookie [-v] [-f filename]
DESCRIPTION
mcookie generates a 128-bit random hexadecimal number for use with the X authority system. Typical usage:
xauth add :0 . `mcookie`
The "random" number generated is actually the output of the MD5 message digest fed with various pieces of random information: the current
time, the process id, the parent process id, the contents of an input file (if -f is specified), and several bytes of information from the
first of the following devices which is present: /dev/random, /dev/urandom, files in /proc, /dev/audio.
BUGS
The entropy in the generated 128-bit is probably quite small (and, therefore, vulnerable to attack) unless a non-pseudorandom number gener-
ator is used (e.g., /dev/random under Linux).
It is assumed that none of the devices opened will block.
FILES
/dev/random
/dev/urandom
/dev/audio
/proc/stat
/proc/loadavg
SEE ALSO X(1), xauth(1), md5sum(1)AVAILABILITY
The mcookie command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
25 September 1995 MCOOKIE(1)
Check Out this Related Man Page
RANDOM(4) BSD Kernel Interfaces Manual RANDOM(4)NAME
random , urandom -- random data source devices.
SYNOPSIS
pseudo-device random
DESCRIPTION
The random device produces uniformly distributed random byte values of potentially high quality.
To obtain random bytes, open /dev/random for reading and read from it.
The same random data is also available from getentropy(2). Using the getentropy(2) system call interface will provide resiliency to file
descriptor exhaustion, chroot, or sandboxing which can make /dev/random unavailable. Additionally, the arc4random(3) API provides a fast
userspace random number generator built on the random data source and is preferred over directly accessing the system's random device.
/dev/urandom is a compatibility nod to Linux. On Linux, /dev/urandom will produce lower quality output if the entropy pool drains, while
/dev/random will prefer to block and wait for additional entropy to be collected. With Yarrow, this choice and distinction is not necessary,
and the two devices behave identically. You may use either.
The random device implements the Yarrow pseudo random number generator algorithm and maintains its entropy pool. The kernel automatically
seeds the algorithm with additional entropy during normal execution.
FILES
/dev/random
/dev/urandom
HISTORY
A random device appeared in the Linux operating system.
Darwin September 6, 2001 Darwin
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