All Questions
395 questions
1
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45
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Usage of Mt_Rand in PHP
I am creating an exericse for my users, where I am trying to tell them that using mt_rand() is not a good option from security point of view. What I did is that I showed them a normal user who gets a ...
- 343
0
votes
2
answers
89
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Is PHP's mt_rand function insecure on every platform?
I was going through this article, https://www.ambionics.io/blog/php-mt-rand-prediction, which claims that if we use mt_rand(), we can get the seed value using two values instead of brute forcing.
In ...
- 343
0
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0
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25
views
exfiltred .rnd file exploitation
Context
During a CTF, as www-data, I managed to exfiltrate an .rnd file used by phpseclib on a PHP app (I exfiltrated the entire app). Since SSHD is configured with PubkeyAuthentication yes and ...
- 111
0
votes
1
answer
131
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Predicting math.random after math.floor
I know math.random() in javascript can be predicted if you know the exact outputs of it, but if I only know what it gives after doing math.floor(100 / (1.0001 - Math.random())), how would I use this ...
1
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0
answers
25
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Is it ok to use NativePRNGNonBlocking SecureRandom for making jwt? [duplicate]
I'm developing jwt auth feature with Spring WebFlux. And, I found the blocking calls in jjwt library by using BlockHound.
The reason of blocking calls was SecureRandom use /dev/random to make random ...
- 11
15
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4
answers
6k
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Security of a non-random password but that relies on information an attacker cannot possibly know
I am trying to figure out whether a non-random password that relies on information an attacker cannot possibly know can be secure.
To give an example, let’s say that I generate my password by putting ...
- 569
0
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0
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49
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What is a secure way to create a random number in Typescript? [duplicate]
I want to create a function that returns a random number in a given range, what is a secure way of doing that?
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-1
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1
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113
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Is encoding random with module insecure? [closed]
The ID library Nano ID claims that modulo based encoding (e.g. Base64) would lead to uneven distribution in the output:
Uniformity. random % alphabet is a popular mistake to make when coding an ID ...
- 99
0
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2
answers
2k
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Can UUID v7 be treated as a unguessable, opaque identifier?
RFC4122bis specifies UUID v7, a version which contains 74 bits of randomness.
Assuming I use a CSPRNG to generate the random bits: Are these UUIDs considered to be unguessable and are enough to ...
- 105
0
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0
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27
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Any idea on how this 36 character long string generated? [duplicate]
I have a personal id "U1KFhYtMqZhCYya6sy31PVLM8DlM5HLCkwy3", I have checked some hash functions but cannot make sure how this generated? Is this just random string generated with [a-zA-z0-9]?...
- 101
1
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1
answer
221
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Which algorithm does CryptGenRandom use on my laptop?
I have an Ideapad Gaming laptop by Lenovo, with an Intel(R) Core(TM) i5-10300H processor. On this laptop I have Windows 10 installed. To generate random numbers, I use the CryptGenRandom function. ...
- 113
0
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1
answer
170
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SecureRandom safety?
I need to randomly pick 10 numbers from 1 to 2000. It is very important that this rng cannot be predicted/hacked in any way. Would this be a safe/proper way to do it:
int randomInt;
SecureRandom ...
0
votes
2
answers
322
views
Is using weak random numbers for the initialization vector of AES just a theoretical issue?
I'm the maintainer of pypdf, a Python library for reading/manipulating PDF documents. I recently discovered that pypdf used random instead of secrets for ...
Generating the initialization vector (IV) ...
- 3,952
0
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1
answer
109
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Randomness of seeded cryptographically secure random number generator
If I generate a large true random number and I seed a CSPRNG with it, then can the output of this CSPRNG be used anywhere where there is a need for a true random number?
For example, if Alice and Bob ...
- 339
5
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5
answers
6k
views
Randomly generated secrets: encoding the random bytes in base64 vs keeping them
Today this came to my attention.
When generating random secrets for e.g. JWT (in node.js the most common way is using the crypto.randomBytes() method), I have noticed a lot of people save these tokens ...
- 169
1
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2
answers
156
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exploiting the scenario and how to generate a secure reset password token
I am using the following line of code to create a reset password code sent to the user in her/his email. when scanned with brakeman to my ruby code, this line of code is catched and describes it as it ...
- 131
1
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3
answers
1k
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Is it possible to retrieve seed from a few random numbers?
Let's say I have generated 16 integers (between 0 and 128) using Python
from random import seed, randint
seed(1234)
randoms = [randint(0, 128) for _ in range(0, 16)]
If we have a rough knowledge of ...
- 13
0
votes
1
answer
155
views
Pre-generate random numbers or generate it on the spot
We are developing a lottery platform, and we are discussing what the best way to implement it would be.
As we have it right now, the system pre-generates, using a TRNG device, all the winning numbers ...
- 103
1
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2
answers
135
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Is there any encryption method that uses TRNGs?
Can we create a true random generator whose entropy source is the loss of electrical signals that a binary architecture cannot detect?
If we have a system that let's say could do this, could we be ...
- 11
1
vote
2
answers
248
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Random identifier vs identifier plus HMAC
Suppose I have a resource that I want to be accessible only using a specific link. I could generate a link using a 256 bit random identifier, e.g. https://example.com/aMXtSQufIxntoMSnTQGdgMfs84VzM-...
- 113
1
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2
answers
308
views
How does /dev/random not leak future bytes from old ones
I want to generate 6 random words using Wiktionary and random numbers from /dev/random. I'll get a random number with /dev/random and then use the word from that index.
I know /dev/random should be ...
- 13
1
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0
answers
326
views
How do in-memory unrandomizers (like in Cheat Engine) work?
Cheat Engine is a rather known memory editing and manipulation tool for Windows.
It has this feature to screw up your randomness generation, how does it achieve it?
My guess would be that it makes the ...
- 1,675
0
votes
1
answer
144
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Why GNU libc's salt alphabet for `crypt` is limited to ./0-9A-Za-z?
According to docs:
To hash a new passphrase for storage, set salt to a string consisting of [a prefix plus] a sequence of randomly chosen characters ...
and
In all cases, the random characters ...
- 103
1
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0
answers
156
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Comparing HAVEGE and Jitter Entropy algorithms
How does the HAVEGE method (or rather, the specific adaption of it as used in haveged) for generating randomness from timing differ from that of the Jitter Entropy method? Is there any research ...
- 67.3k
16
votes
5
answers
6k
views
Pseudorandom vs. True Random
Proper security algorithms demand true random numbers. For instance, secret keys & initialization vectors should never not be true random.
However, generating numbers using Java's Random library ...
- 287
0
votes
1
answer
168
views
Is it necessary to use cryptographically-secure randomness in order to create URLs for user activation?
Usually once you register in a website you need to visit a url like:
https://example.com/user_activate/^random_string^
Does the ^random_string^ necessarily need to be cryptographically pseudorandom ...
1
vote
1
answer
207
views
Should a user refill their 2FA when they login into a different account and back?
Some of our users on our website have two or more accounts they use to log in. With each device they log in a specific device ID is generated. This device ID is stored on the device itself and on the ...
- 113
1
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1
answer
326
views
Can I evaluate the quality of my OS random numbers? [duplicate]
Is there a software or website that implements tests of randomness to check if my random numbers are of cryptography quality ?
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11
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2
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8k
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Is "Math.random" the same as "crypto.getRandomValues" (JavaScript security)
This question may be a little off-topic, but is Math.random the same as crypto.getRandomValues? (JavaScript)
Here's an example:
Math.random(); // 0.11918419514323941
self.crypto.getRandomValues(new ...
- 289
1
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0
answers
592
views
How many random characters must an unguessable string contain?
I want to add a suffix to my URLs that makes them distinctive and therefore only findable by a person who knows that suffix. I considered using a UUID or hash, but these are usually very long. However,...
- 127
1
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1
answer
361
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Does combining a non-cryptographically secure string with a cryptographically secure string result in a cryptographically secure string?
I'm using php, but the general question applies to any confirmed cryptographically secure pseudo-random string concatenated with a non-cryptographically secure string.
I know random_bytes generates a ...
- 366
10
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6
answers
4k
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Can iterated hashes be used to create cryptographically secure random data from strong random seed?
I was wondering if generation of sequential hashes from random seed can be considered "random enough" to be used in cryptographic operations?
By sequential hashes I mean the following:
First ...
1
vote
1
answer
211
views
Verifying public key visually
Verifying a string of long numbers is hard (think of cert public key). I remember there is a tool to visualize this randomness into a "randomness graph" but I cannot recall what is the graph ...
- 113
2
votes
3
answers
2k
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Is a simple random+hmac session cookie breakable?
I make session cookies of form session_id+'|'+hmac_sha256(session_id, static_secret) where session_id = random_string(16 bytes) made with a PRNG (not a CSPRNG!) seeded on the server's timestamp at ...
- 123
1
vote
1
answer
542
views
Randomness of hash of (password + suffix)
Suppose I have a password, say "thisIsThePassword".
Then I have MD5 hashes of that password followed by an increasing numeric suffix:
MD5("thisIsThePassword1") = ...
- 15.9k
0
votes
3
answers
809
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(...
- 226
1
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2
answers
257
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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 ...
- 177
3
votes
1
answer
2k
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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 ...
- 31
0
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1
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279
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 (...
2
votes
5
answers
1k
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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 ...
- 194
5
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1
answer
301
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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 ...
- 171
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1
answer
428
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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 ...
0
votes
1
answer
770
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'...
1
vote
2
answers
333
views
How to select a random node when nodes are untrusted in a distributed network?
Assume in a distributed network, where the nodes are not trusted and are identified by their public keys, we intend to select one of them in a random process. In such a situation, all of the nodes ...
- 1,357
0
votes
0
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421
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 /...
- 101
0
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1
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818
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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-...
8
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2
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370
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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, ...
- 275
6
votes
2
answers
4k
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?
- 61
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0
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512
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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 ...
- 215
3
votes
1
answer
289
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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