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Questions tagged [random]

The generation of random or pseudorandom data, and the use of randomness in security protocols

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1answer
55 views

What does “probabilistic algorithm with random tape” mean?

I am new to the study of cryptography, and when reading papers they often mention that "probabilistic algorithm G with random tape w ...". What does it mean by "random tape w"? I mean why it does is ...
2
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1answer
91 views

Is it safe to use a passphrase to seed fernet key generation?

I have a cluster deployment that depends on a Fernet Key to secure some data. The deployment script generates the key with: FERNET_KEY=$(python -c "from cryptography.fernet import Fernet; k = Fernet....
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0answers
39 views

Can Lava Lamps enhance modern native entropy sourced from hardware and the Linux Kernel? [duplicate]

In this 2017 video by Computerphile's Tom Scott, "The Lava Lamps That Help Keep The Internet Secure", Scott tours Cloud Flare's facility and checks out their Wall of Entropy. This is essentially a ...
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1answer
148 views

How can I increase /proc/sys/kernel/random/entropy_avail

I have access to genuine random numbers - random.org, for example. I have a number of processes using /dev/random and my value for /proc/sys/kernel/random/entropy_avail is 143, which is pretty low. ...
4
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1answer
117 views

Is pressing random keys a secure way to seed a key generator?

There's a couple of programs that I've been using recently that ask you to type random keys as a source of randomness to seed an RNG for key generation. Is this considered a good practice still, or ...
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2answers
333 views

What research suggests that user's mouse movements are (not) sufficiently unpredictable for secret key generation?

I have not been able to find any credible source which tried to prove or disprove the randomness of mouse movements. A Google Scholar search for "mouse movement entropy" gives surprisingly few ...
7
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3answers
281 views

Is PuttyGen secure?

I'm using PuttyGen to generate ssh keys for various windows computers. It requires a lot of manual user input, specifically in the form of swirling the mouse around in the window pane. I understand ...
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2answers
64 views

How to solve the problem of secure randomly generated GUIDs when the size of the data outgrows the GUIDs

I've been struggling with this problem for a little while... How to hide the order that records were created in, basically. You typically do this by generating a "GUID". But this GUID is arbitrarily ...
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1answer
74 views

Size of a secure random number taking into account quantum computing and size of universe

Most random secure numbers are 256 to 512 bits. But given the size of the universe and eventually quantum computing, I am wondering what is a better sized randomly generated number, taking into ...
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0answers
44 views

Does using both a counter and a random nonce make sense for the purpose of reducing the likelihood of replay attacks?

I am aware that using a counter or a random value are both acceptable ways of generating nonces, depending on the circumstances. The tradeoff with using a counter is the necessity to keep state and ...
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2answers
1k views

Is there a loss of entropy by hashing an N-bit random key to produce an N-bit hash?

I read the following piece of code: dd if=/dev/urandom bs=16 count=1 2>/dev/null | md5sum Apparently, this code was used as a trick to produce a hex string key from a 128-bit binary pseudo-random ...
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1answer
89 views

What is the entropy of a call to java.lang.Math.random()?

Math.random() produces a double value (IEEE 754 binary64) in the range [0.0, 1.0). How many digits (or bits) of entropy does the return value of random() contain? If it simplifies things, I'm okay ...
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3answers
162 views

What should a secure passphrase look like?

We all know that passwords should not only be randomly generated, but also look random. The reason is that attackers can use patterns or existing words to be able to bruteforce the passwords faster, ...
3
votes
1answer
69 views

How do GnuPG smartcard generate reliable random data?

I'm generating a private key on my new GPG smartcard at this very moment. On linux, the random would be fed by the keystrokes on my keyboard, the network packets, the mouse movements etc. How does ...
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4answers
248 views

Are there any practical attacks on random number generators?

I'm creating an internal security course for developers. To make it more interesting, I'm trying to reinforce each chapter with some real-world attacks but stumbled upon insecure random usage section. ...
2
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3answers
181 views

Password-hash proofing SHA-3

I am in a situation where I need to harden a password hash, but not allowed to bring in any extra dependencies, so I am pretty much forced to do the one thing everyone seems to advise against - roll ...
0
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1answer
39 views

Is it necessary to verify that my order confirmation IDs are unique?

I'm generating 9-character order confirmations such as K1YBFRG17, O1D15ZCOM, etc and using them as order confirmation numbers. It's basically just picking at random from the string '...
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1answer
85 views

The NIST randomness tests for a generated key

Does different tests for key randomness provided by NIST are available online? where one can test that which test for key generated are passed and which are failed?
2
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1answer
181 views

Is RDRAND used in a safe way by Windows 10?

This question was already answered by Linus Torvalds for Linux, and is also cited in this Q/A on this stack: We use rdrand as _one_ of many inputs into the random pool, and we use it as a way to ...
2
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2answers
191 views

When you XOR a random number with non-random number, does that give you a new random number?

XOR has the following truth table: 0, 0 : 0 0, 1 : 1 1, 0 : 1 1, 1 : 0 So per bit in an XOR operation, there is a 50% chance of that result being 1 and 50% chance of it being 0. If you XOR a random ...
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2answers
61 views

Should you use SecureRandom.getInstance() with or without a provider?

So, I am new to cryptography and I was learning about SecureRandom and all of the ways it calls implementations with or without providers. When I looked up some sites for information, it says not to ...
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2answers
228 views

/dev/random generate session key

if a server uses /dev/random to generate the random session key with a client. How you can launch a Denial-Of-Service (DOS) attack on such a server?
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1answer
111 views

Mobile application authentication using UUID

I write back-end code for mobile applications. I am needing to write the code for authentication and the simplest yet secure solution I can think of is: When user signs in, device sends username and ...
2
votes
1answer
121 views

For a “normal” computer user, does it make a difference to have a good entropy source?

Let's take, for example, Linux. From my understanding, there are different sources and different ways that can be used to gather entropy (RNG daemon, Intel rrandr, TPM, etc). Some produce entropy that ...
72
votes
5answers
14k views

What makes Random Number Generators so fragile?

It seems to me that a hardware component which generates random numbers is extremely simple - just measure tiny vibrations in the hardware with a sensor, right? Maybe I'm wrong but it seems like if ...
1
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1answer
87 views

What function is used to generate client random in TLS

I've been learning TLS. During the Client-Server Hello their random values are shared. The client generates a 28 byte random and combine it with 4 bytes of epoch time to generate a 32 byte random ...
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1answer
199 views

How to reverse engineer str_shuffle (PHP) to get its mt_rand outputs

$output = str_shuffle("12345"); E.g. $output is now 25134 How do I find out what numbers came out of mt_rand() to allow for the shuffle I want to know this because I want the seed of mt_rand() and ...
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1answer
163 views

Is a substring of base64 encoded random_bytes less secure then just using random_bytes

$bytes = random_bytes(15); $encoded = base64_encode($bytes); $output = substr($encoded, 0, 15); Does this code affect the complexity of the output vs just using $output = random_bytes(15); I think ...
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1answer
235 views

Would `cat /dev/random` be a denial of service to any other users of `/dev/random`?

As in the question. Wouldn't cat /dev/random decrease the entropy estimate until it blocks, which forces the random device to block for all applications on the current system?
21
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2answers
3k views

Is “always use /dev/urandom” still good advice in an age of containers and isolation?

In short: Instead of another question asking about when to use /dev/random instead of /dev/urandom, I present the following scenario, in which I find myself in an application I'm building: A VM or ...
1
vote
1answer
152 views

Does OpenSSH use padding of random lengths?

According to the end of RFC 4253 § 6, the random padding introduced to each SSH packet is an arbitrary multiple of 8. It mentions that random padding lengths can mitigate traffic analysis: Note ...
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1answer
207 views

Injecting data into the Windows entropy pool

On Linux, it is possible for userspace to mix arbitrary data with the kernel entropy pool by writing to the /dev/urandom device. Is there any equivalent on Windows which does not require SYSTEM?
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0answers
133 views

Problem in Cracking PHP rand() seed on windows

I read this article https://www.sjoerdlangkemper.nl/2016/02/11/cracking-php-rand/ about cracking php rand() function. and I involved with some problems on testing methods mentioned in article. I used ...
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1answer
2k views

How to correctly use dev/urandom for random generation [closed]

Runs before main: d -c 30 /dev/urandom > random.bytes Access the randomly generated numbers int main() { FILE *fp; int fd = open("random.bytes",O_RDONLY); fp = fopen("file.txt" , ...
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votes
1answer
604 views

Unix command to generate cryptographically secure random string

Is the following Unix command cryptographically secure to randomly generate 20 characters (a-zA-Z0-9 only)? dd if=/dev/urandom bs=256 count=1 2> /dev/null | LC_ALL=C tr -dc 'A-Za-z0-9' | head -c20 ...
10
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1answer
269 views

Random seed not propagating to the entropy pools in a timely manner

The Linux kernel's randomness driver collects entropy from the environment. Because there will be little entropy during boot, a random seed is often kept at /var/lib/misc/random-seed or a similar ...
3
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0answers
238 views

Entropy sources used by modern Windows

A comment on a Microsoft blog from 2005 mentions over 150 sources of entropy for the Windows CryptGenRandom function. The majority of sources come from low-level system information (precise stat ...
212
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11answers
42k views

Why is Math.random() not designed to be cryptographically secure?

The JavaScript Math.random() function is designed to return a single floating point value n such that 0 ≤ n < 1. It is (or at least should be) widely known that the output is not cryptographically ...
3
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1answer
133 views

Linux 'add_interrupt_randomness' implementation - low entropy contribution by cycles and jiffies?

Currently I'm analyzing the process of entropy generation of a Linux 64-bit kernel during system startup (for educational purpose). The system is hosted as/on a (64 bit) virtual machine (Xen domU). ...
3
votes
1answer
5k views

Need advices on API key & secret generation?

While working on a Java project using Spring-boot, Spring-security and JWT token, I need to provide access via API key and secret. After searching on Google for a while about key/secret generation, ...
0
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1answer
72 views

Key Generation on FIPS device or using SW with FIPS generator

I would like to understand the difference between these two options how to generate AES key. AES key is generated directly in FIPS 140-2 Level 3 device with validated AES algorithm AES key is ...
2
votes
3answers
135 views

XOR of many prime sized cycles: secure?

I thought of a PRNG which is dependent on a large amount of good salt. The method is to use the salt to fill many arrays whose lengths are prime numbers, and cycle through each array, and ouput the ...
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vote
1answer
134 views

Generating a secret on a compromised computer

Suppose we are on a compromised computer (for example infested with trojans logging key presses or taking screenshots) and for some reason we have to generate a number that's supposed to be secret for ...
4
votes
2answers
263 views

What role do hashing and block ciphers play in random number generation?

I read about pseudo random number generators and there were certain demands on which "underlying hash function" and "underlying block cipher" to use. What role do hashing algorithms and block ciphers ...
5
votes
1answer
173 views

How would someone attack a not truly random secret produced by a human?

Especially in cryptocurrencies you often hear people say that private key/seeds should not be typed "randomly" by humans, but rather use a truly random number generator. I understand, that humans ...
3
votes
1answer
195 views

Are many rounds of SHA needed for a random veracrypt key

Assume that I've used white noise from the classic "zener breakdown" circuit to produce 512 bits of random data. If I use these as the key to a Veracrypt volume, is there any benefit to running 200,...
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2answers
922 views

Is it possible to predict Python's random.random() if it is constantly seeded with high entropy values?

I am interested in understanding if it is possible to predict Python 3 random.random() when seeded with high entropy value from a physical system, like a dice toss. In other words, is random.random() ...
2
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3answers
606 views

Does the existence of two-factor recovery codes mean that my 2-factor code isn't completely random?

With some services that use standard 6-digit TOTP codes, they also offer the ability to have a set of backup codes, in case you lose your two factor device. With Google, for example, you can print ...
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1answer
244 views

Most widely used non Cryptographic random number generators

I want to research pseudo random number generators, and I see that a lot of the random number generators are not as secure as people assume. What I would like to know is what are the most widely used ...
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0answers
80 views

What's the difference between random number evaluation among AIS-31 AIS-20 and NIST sp800-22

I'm trying to know about the evaluation of random number generated by smart card chip. But these standards AIS-31, AIS-20 and NIST sp800-22 confuse me. Could someone help me with a brief explanation ...