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

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48 views

How many bytes for password reset token? Should one take steps to hash or conceal raw CSPRNG bytes?

I'm trying to follow the OWASP 'Forgot Password Cheat Sheet' recommendations for password reset functionality via email. This requires my server to generate a token. OWASP says that PHP's random_bytes(...
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2answers
120 views

Is it bad to reveal random bytes from a system?

Let's say you cat /dev/random or /dev/urandom all day from boot to system shutdown, either redirecting the output to a file, or just catting it (in a terminal, or whatever) doesn't matter. Is this ...
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1answer
76 views

Is Python's `secrets` module using the same code as the `random` module?

The secrets module is marketed as a safe alternative to random for things that are meant to be secret. But what's the actual difference? Looking at their code, in some cases these libraries actually ...
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1answer
78 views

Are weak entropy sources worth it?

I maintain an operating system that can be deployed to embedded devices with highly diverse capabilities. One of the aspects of porting the OS to a device is declaring the available entropy sources (...
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5answers
219 views

Attacks Relying on Poor Entropy

I'm creating a quantum random number generator as part of my thesis. As part of the research phase, I'm trying to substantiate my aspertion that encryption is significantly weakened if a computer ...
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1answer
125 views

Security Implications of Caching Randomness

Is it a bad idea to cache randomness in the general case? My feeling is yes, but I'm having a hard time articulating why. Scenario: A programming language of your choice (e.g. node) uses a native call ...
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1answer
114 views

What is “environmental noise”?

I'm looking at way to generate random numbers for cryptographic purposes. More specifically, I looked at the Linux /dev/urandom function, which is considered a real random number generator. There are ...
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1answer
124 views

So I just got a voicemail from a random person, where it says 3 random numbers (for example 354) and then “goodbye” [closed]

So basically, i was just playing games as always, and I get a voicemail. It reads-"396 (random numbers just incase the numbers are sensitive information), goodbye" It sounds automated but i'...
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0answers
42 views

Weird GET request on internet facing Nginx [duplicate]

I spun up an internet facing nginx server in AWS and the logs started showing weird get requests with a search engine's spider as user agent. 172.31.43.193 - - [19/Aug/2020:20:09:19 +0000] "GET /...
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1answer
107 views

Security of PHP's str_shuffle()

I'm doing some research on PHP's str_shuffle function, I already asked this question multiply times on StackOverflow but got no answer https://stackoverflow.com/questions/61968859/is-it-possible-to-...
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2answers
241 views

Randomly selected words converted into sentence. Did I lose passphrase strength or gain it?

I got 5 dice and opened EFF's wordlist, and generated a random five-word passphrase (all letters small with spaces, no punctuation) for my PC. The words were making up a meaningful scene in my mind, ...
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1answer
911 views

Is it cryptographically safe to use veracrypt in a virtualbox virtual machine?

Does virtualbox provide enough entropy (random numbers) for the veracrypt program on the virtual machine? Is it cryptographically safe to use veracrypt inside a virtualbox in a windows 10 guest?
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67 views

Random URLs to hide assets [duplicate]

Say I own a domain name www.example.com and I'd like to host some resources on it, but being reasonably hidden from the public. Since a 256 bits has a sufficiently large entropy to prevent an ...
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1answer
73 views

Randomly generating invoice IDs

I'm in the process of setting up a local (i.e. offline and very limited) business, and I'm thinking of generating invoice IDs randomly to avoid the clients knowing that they're customer number #...
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1answer
148 views

Did PHP's rand() get better?

I know that PHP used the system implementation for its rand() function, which is usually a weak LCG or LFSR implementation. Did this change? In case it still does, I am using Fedora 32. PHP states in ...
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3answers
78 views

Is a random number secure (enough) for card numbers and pins?

I've been given the task of generating some gift tokens which comprise a serial number and a pin number, analagous to a pre-paid credit card. The serial and pin will be printed on a card, with the pin ...
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33 views

Is it possible to exploit “naive” shuffling algorithms to find the original order?

This Coding horror article talked about the danger of "naive" shuffling solutions and how using the Fisher-Yates shuffle manages to prevent this problem. If one has a large dataset of naive shuffle ...
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56 views

Generating trusted random numbers for a group?

Alice and Bob need to share some cryptographically-secure random numbers. Alice does not trust Bob, and Bob does not trust Alice. Clearly, if Alice generates some numbers, and hands them to Bob, Bob ...
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1answer
122 views

What vulnerabilities would this type of “password manager” have?

When I was searching for a password manager to use I stumbled upon the concept of Master Password which instead of encrypting and saving your passwords, generates them by using your master password ...
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1answer
44 views

Does OAuth2 state parameter need to be cryptographically secure?

In OAuth2, as part of the authorization request, we generate a random string and pass it with the state parameter, so that when we get the response, we can ascertain that the response is a result of ...
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1answer
173 views

Does rngd -r /path/to/file inject into /dev/urandom in addition to /dev/random?

I'm new to the /dev/random and /dev/urandom pipes in general and have an application calling from /dev/urandom which I'm attempting to inject entropy into. I'd prefer not to change the source for ...
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0answers
46 views

Anonymous (privacy-preserving) random walk

Quoting this paper - SmartWalk (https://dl.acm.org/doi/pdf/10.1145/2976749.2978319): For graph privacy, strong link privacy relies on deep perturbation to the original graph, indicating a large ...
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0answers
42 views

Anonymous (privacy-preserving) random walks for graphs

Quoting this paper - SmartWalk (https://dl.acm.org/doi/pdf/10.1145/2976749.2978319): For graph privacy, strong link privacy relies on deep perturbation to the original graph, indicating a large ...
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1answer
117 views

Cracking .NET random

I know .NET has two PRNGs, one secure and one insecure. What is the approach to cracking the insecure one (I want to use it to test an .aspx site)? I searched all over but I only found references to ...
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2answers
101 views

Should I generate a lot of random serial keys and pick one for each registration or generate 1 for each user?

I'm talking about Online activation. My current workflow is: User pays via paypal (without registration) Paypal performs a request to my API. My API returns a serial key to the user. Then the user ...
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1answer
96 views

How can I validate that a PRNG's output is insecure and predictable?

Say I talk to a developer who is using some output of a Pseudo-random number generator in order to do some security task. I know based upon common knowledge that only Cryptographically Secure Pseudo ...
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3answers
199 views

How can one test if a password generator is cryptographically secured?

Given the plethora of random password generators (RPG) available, I'd like to do some black box testing on some. Let's take https://passwordsgenerator.net/ for example. Assuming the whole generator ...
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0answers
203 views

Is it safe to generate a temporary API key from a random generator seeded by a secure random generator?

I have a need to generate a key consisting of a given number of random characters that will be used to access resources via a public API. It should not be possible to predict the key. This is done in ...
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1answer
2k views

Is reading from /dev/urandom on macOS Catalina a safe way to produce cryptographically secure data?

I'm reading a lot about entropy on macOS... I know it doesn't use Yarrow anymore as per this FIPS 140-02 doc a NIST compliant DRBG. I read a lot: https://github.com/briansmith/ring/pull/398 How ...
2
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1answer
222 views

entropy change when reading from /dev/urandom vs /dev/random

I noticed that when reading from /dev/random, I have a very real impact on the entropy available on my linux box. (reading from /proc/system/kernel/random/entropy_avail), Yet when reading from /dev/...
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0answers
73 views

Is it possible to get the original UUID1 from a timestamp?

Say, for example, I generate a time based UUID with the following program. import uuid uuid = uuid.uuid1() print uuid print uuid.time I get the following: 47702997-155d-11ea-92d3-6030d48747ec ...
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1answer
198 views

using HW random number generator as source of entropy

Currently I am using haveged on my server as source of entropy. My Server is used as KVM hypervisor, to run virtual machines. I did not use haveged at the beginning, and I noticed the VMs were ...
2
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1answer
131 views

TLS handshake random bytes reused

What would happen if the random bytes provided by the client and the server in the first two messages would be reused by one peer/by both peers? I think it would highly reduce the provided security, ...
2
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1answer
122 views

Is this schema between a Desktop App and an API secure?

From my previous question: How secure is this schema between a Desktop App (c++) and an API (php). Introduction I made a paid Desktop-app that required constant internet connection (because of its ...
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3answers
92 views

Benefits of signing a random number?

Is there any benefit to signing a random number? E.g. a link for password reset, sent to email, often includes a base64 encoded random number to prevent someone guessing what the password reset link ...
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2answers
127 views

If I seed a CSPRNG with a truly random number and call the output, does this make the number more, less or equally “random”?

If I have a JavaScript CSPRNG such as isaac.random(), and I seed it using a truly random number T as such: isaac.seed(T), does this make the result of the CSPRNG more, less, or equally random? I ...
3
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1answer
171 views

What are some viable, secure sources of entropy for a CSPRNG?

I need some viable sources for entropy to seed a CSPRNG. So far, I have: JS Events Web Crypto API performance.now() Timing for xmlHTTPRequests etc. Are there any other viable/secure entropy sources ...
2
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1answer
84 views

Is getting 1-2 outputs from a CSPRNG to seed another CSPRNG less entropy than getting say 5000 outputs from a CSPRNG and using that to seed?

This question builds off of this question. I want to create more entropy from a viable entropy source to seed another CSPRNG. If I use window.crypto.getRandomValues(newUint8Array(1)) To seed a ...
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3answers
115 views

Is using multiple instances of a browser-PRNG to seed another PRNG more secure?

Say I have Math.random() (which supposedly generates ~32 bits of entropy.) If I use Math.random() + Math.random(), both of them generate ~32 bits of entropy. I will use the solution of Math.random() +...
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1answer
209 views

Find seed used in Math.random LCG given a list of outputs [duplicate]

Given one or two sequential Math.random outputs generated with Internet Explorer's linear congruential generator, is it possible to find the seed used in the LCG and find subsequent outputs? Here is ...
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1answer
679 views

Predicting Math.random() sequence using V8's MWC1616 algorithm

If you have the seeds for Math.random() using mwc1616, are the random numbers generated in the same order every time / are they repeating? Basically wondering if, given a seed, can I predict past ...
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0answers
292 views

How long will it take to crack a hashed random string

If I generate 128 bit, 512 bit and 1024 bit random strings using either: A native rand() function (C, PHP, Python, etc) OpenSSL random bytes Hardware generated random number And hash the random ...
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0answers
59 views

Generating a secret token: security concerns other than min-entropy?

I'm trying to compare two techniques for generating an OAuth 2 PKCE code_verifier. For each character, get a random byte and "mod 66" to map to one of the 66 valid characters. For each character, get ...
3
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3answers
523 views

Determining the entropy of a string if each character has a slight bias

Let's say I need to generate a 32-character secret comprised of ASCII characters from the set '0'..'9'. Here's one way of doing it: VALID_CHARS = '0123456789' generate_secret_string() { random =...
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1answer
119 views

Am I making my One-Time Passcode less secure?

I am using some "magic link" one-time passcodes for automatically logging users in for a specific purpose on our website. My plan is to generate a hash based on the datetime, users specific "ID" and ...
2
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3answers
670 views

Exactly how is a pseudorandom number generator a security risk?

I was recently reading about Diceware, which is essentially a list of words from which several can be picked to form a long passphrase. The website stresses that these words should be picked randomly ...
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1answer
119 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 ...
3
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1answer
642 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
50 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 ...
2
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1answer
2k 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. ...

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