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0
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2answers
43 views

check two partitions by selecting random files and running sha1 hashes on two files of each partition

A previous answer to a post mentions to run sha1 hashes on an images of a dd drive clone image. Another answer to that post suggests mounting the dd image an then compare if the sha1 hashes of ...
2
votes
1answer
52 views

Generating file with ASCII numbers using /dev/urandom?

How can I generate 10 MB files from /dev/urandom filled with: ASCII 1s and 0s ASCII numbers between 0 and 9
1
vote
0answers
118 views

How to debug random reboots, with no kernel panic, of an embedded system?

I have two aValue RPC-10W1 embedded systems that reboots by themselves after 1-2 hours. Facts: The board will reboot within a time span of 1 to 2½ hours. The issue is present on two identical ...
15
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2answers
1k views

Why writing to /dev/random does not make parallel reading from /dev/random faster?

Typically reading from /dev/random produces 100-500 bytes and blocks, waiting for an entropy to be collected. Why doesn't writing information to /dev/random by other processes speed up reading? ...
3
votes
4answers
196 views

Generate random numbers in specific range

After googling a bit I couldn't find a simple way to generate with a shell command a random number included in a specific range, between a minimum and a maximum. I read about /dev/random, ...
6
votes
2answers
373 views

Adding “random number entropy” for GPG keys?

In the following video: Linux HOWTO: Secure Your Data with PGP, Part 2, you are shown how to create a key pair with gpg. At about 1:50, the instructor says the following: While the key is being ...
0
votes
0answers
43 views

xdotool random/more natural delay?

For automated testing of some applications, I would like to emulate the users behaviour. I know I can user the xdotool type --delay option, but I would like a more natural delay. The easiest thing ...
2
votes
4answers
169 views

Overwriting a Disk

Should I use: find / -type f -exec shred -uvz -nX or just good old dd if=/dev/urandom of=/dev/sda Is one faster or more secure than the other?
7
votes
1answer
120 views

/usr/bin/random using a lot of CPU

Using QNX 6.4.1, there is a command called pidin times that shows information about processes. I think it means PID INformation. Among other things, you can see how much CPU a process has used since ...
6
votes
1answer
193 views

Can you explain the entropy estimate used in random.c

/dev/random uses the timings of kernel interupts to add to the entropy pool. The amount of entropy in the pool is tracked in a variable named entropy_count. Here is the relevant snippet of code from ...
6
votes
2answers
612 views

Create random data with dd and get “partial read warning”. Is the data after the warning now really random?

I create a 1TB file with random data with dd if=/dev/urandom of=file bs=1M count=1000000. Now I check with kill -SIGUSR1 <PID> the progress and get the following: 691581+0 Datensätze ein ...
7
votes
2answers
1k views

RSA 2048 keypair generation: via openssl 0.5s via gpg 30s, why the difference?

RSA 2048 keypair generation: via openssl 0.5s via gpg 30s, why the difference There are several programs which can gerate RSA public/private keypairs GnuPG/OpenPGP for instance has a wizzard being ...
4
votes
1answer
134 views

measure amount of data read from /dev/random

background I have written a collection of bash scripts (most of them in German only yet but if you are interested; download the archive not the single scripts) which help users create high-quality ...
5
votes
3answers
2k views

Reading from /dev/random does not produce any data

I often use the command cat /dev/urandom | strings --bytes 1 | tr -d '\n\t ' | head --bytes 32 to generate pseudo-random passwords. This doesn't work with /dev/random. Specifically cat ...
5
votes
1answer
68 views

What does this command actually cause?

Once while talking with my friend I was trying to joke that we might stand a better chance of completing our project if we just run loads of random programs and expect one of them to solve our ...
10
votes
4answers
584 views

Shuffle file randomly with some additional constraints

I have a huge music playlist and, while some artists have many albums, others have just one song. I wanted to sort the playlist so the same artist won't play twice in a row, or his songs won't end up ...
4
votes
2answers
605 views

What keeps draining entropy?

If I do watch cat /proc/sys/kernel/random/entropy_avail I see that my systems entropy slowly increases over time, until it reaches the 180-190 range at which point it drops down to around 120-130. The ...
2
votes
1answer
312 views

Use the raspberry pi as a source of entropy for /dev/random

I'm trying to see if I can use my raspberry pi's hardware RNG as a source of entropy for /dev/random. Mostly to see if I can get it to work and find yet another use for this nifty little device. Of ...
2
votes
2answers
117 views

Feeding /dev/random with disk reads etc

Is there any way to feed /dev/random with sufficient entropy? The data doesn't have to be truly random, i.e. I can append time of day with pid and add 27 to it, it doesn't matter I just want to make ...
1
vote
1answer
374 views

Starting rng-tools in SLES guest in VirtualBox

I am trying to start rng-tools in a SLES 11 SP3 installation inside of VirtualBox. vagrant@sles11sp3x64:~> uname -a Linux sles11sp3x64 3.0.93-0.8-default #1 SMP Tue Aug 27 08:44:18 UTC 2013 ...
4
votes
2answers
281 views

How to determine which processes are using how much entropy from /dev/urandom

Doing fuser -v /dev/urandom tells me which processes currently have /dev/urandom open, but only that. Is there any was to determine anything about how much entropy each one is using up over time? ...
0
votes
1answer
76 views

Random bug in Linux

Some time ago, I remember reading an article on randomization in computing, and how random you can actually get a system to be. The article came about, if I'm not mistaken, because of some seemingly ...
0
votes
2answers
78 views

Daemon not running when started over ssh

I'm trying to start the rngd daemon by remotely starting it via ssh. Unfortunately it does not seem to run until I log onto the machine. The command I'm using is: ssh -n -o StrictHostKeyChecking=no ...
15
votes
3answers
854 views

Run commands at random

I want to run one of the two commands C1 and C2 at random. How do I do that on commandline (bash)? Will appreciate if a one-liner is possible.
3
votes
2answers
305 views

Why doesn't `head -c 2 /dev/hwrng` work?

I have an Atmel 97SC3201 in my computer and set the following in the kernel: CONFIG_HW_RANDOM_TPM CONFIG_TCG_TPM CONFIG_TCG_ATMEL /dev has tpm0 and hwrng, but running this command returns the ...
3
votes
3answers
2k views

Fast Way to Randomize HD?

I've read about how to make hard drives secure for encryption, and one of the steps is to write random bits to the drive, in order to make the encrypted data indistinguishable from the rest of the ...
7
votes
1answer
2k views

Writing /dev/random to file?

If you ran the following, what would happen? cat /dev/random > ~/randomFile # don't run Would it be written until the drive runs out of space, or would the system see a problem with this and ...
7
votes
3answers
4k views

Why can't tr read from /dev/urandom on OSX?

A colleague suggested creating a random key via the following command: tr -dc A-Za-z0-9_\!\@\#\$\%\^\&\*\(\)-+= < /dev/urandom | head -c 32 | xargs It gave me the error: tr: Illegal byte ...
1
vote
2answers
1k views

random number needed

I need a command line script that will generate a random integer between 1 and 6. I'm using Ubuntu with bash. I was working on this a couple of months ago using 'bc', but never got it to work ...
0
votes
2answers
238 views

How to generate Zipf-like samples, by using scripting language

Is there any scripting language function (like in python or bash) that samples from a zipf-like distribution, for exponent 0<a<=1. PS: I am aware of existence of a numpy function that can ...
19
votes
2answers
7k views

How can I populate a file with random data?

How can I create a new file and fill it with 1 Gigabyte worth of random data? I need this to test some software. I would prefer to use /dev/random or /dev/urandom.
17
votes
3answers
4k views

Why does dd from /dev/random give different file sizes?

I am running the following command on an ubuntu system: dd if=/dev/random of=rand bs=1K count=2 However, every time I run it, I end up with a file of a different size. Why is this? How can I ...
9
votes
3answers
2k views

Tool for measuring entropy quality?

Is there a tool available for Linux systems that can measure the "quality" of entropy on the system? I know how to count the entropy: cat /proc/sys/kernel/random/entropy_avail And I know that some ...
-1
votes
2answers
2k views

How to generate random IP addresses

$ nmap -n -iR 0 -sL > RANDOM-IPS-TMP.txt $ grep -o "[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*" RANDOM-IPS-TMP.txt | egrep -v "10.*|172.[16-32].*|192.168.*|[224-255].*" > RANDOM-IPS.txt egrep: Invalid ...
6
votes
3answers
780 views

Lightweight utility/program to run a command after a random delay

I need to randomize the time before a given command starts. I realize it's relatively trivial to do this within a script, or to write a "wrapper" script to do this, but I'm wondering if anyone knows a ...
7
votes
1answer
965 views

Is /dev/random data a psuedo-random AES cypher, and where does the entropy come from?

My current understanding of an entropy pool is that it gathers truly random bits of data at a slow rate. I'd like to know how Unix & Linux collect entropy, and how that entropy is used by ...
5
votes
2answers
3k views

dd if=/dev/random is 'randomly' bottlenecked with BIG time lags, but I have no idea why

I get wildly different real times when I run the following command. dd if=/dev/random bs=1k count=1 It doesn' happen for if=/dev/null, nor does it happen for if=/dev/urandom I've run it 500 ...
1
vote
3answers
1k views

How can I randomize file names in a given directory?

Ok, this may sound like an odd request but it really has a good purpose! I have a Panasonic Plasma TV with an SD card slot, via which I can display a slideshow of JPEG photos. This is useful for ...