Questions tagged [entropy]

In computing, entropy is the randomness collected by an operating system or application for use in cryptography or other uses that require random data. This randomness is often collected from hardware sources, either pre-existing ones such as mouse movements or specially provided randomness generators.

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Should I be concerned if a website has password restrictions that reduce complexity?

Chase banking has two odd restrictions on their accepted passwords. Passwords have a maximum length of 32 characters Passwords can not contain special characters or punctuation I am a software ...
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How many bits of entropy should a password have to be reasonably future proof (10+ years)?

I’ve seen estimations that the NSA is capable of at least 1 trillion (PGP pass phrase) guesses per second, which would mean a password with 80 bits of entropy would take, on average, over 15,000 years ...
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What is the entropy of a password made from the initial letters from an English sentence [duplicate]

One way to build a password is to take the first letter from each word in a sentence. For example, the password "Itsfrqbtwaawwnsl" comes from the sentence "I tried searching for related ...
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How much entropy is needed for encrypting data locally?

I understand that, when storing data on the cloud or something else that might get leaked to the public, the security margin should be at least 128 bit, 256 bit should be used for data that should ...
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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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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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Does a TPM replace the default device's security, or add to it?

Does a TPM replace the default device's security, or add to it? I will try to re formulate it into 2 questions, just to explain what my question is, since I am not very good at English writing. If we ...
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Why use entropy at all in considering password strength?

I don’t understand the password vs. passphrase analyses that I read. Let me explain. Here is a pass phrase. It has 5 words using only lower case (I’m ignoring randomness for this purpose): friend ...
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Feeding entropy pool with my own data [duplicate]

Let's state that I have a huge bunch of truly unpredictable random data in file "random.bin". The random data has been created outside of my system and has been securely transfered into my ...
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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-...
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Chance of guessing any valid credit card data

What's the chance of guessing valid credit card data that could be used to make a payment online? To me, it looks like it's not extremely hard to guess, but I'm not able to calculate the probability. ...
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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, ...
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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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How long does a secret URL need to be?

I'm currently creating a small service where users can upload images (just a free time project). The images are either private, public (unlisted) or public (listed). Now I'm wondering for public ...
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Specific character based policy for passwords

I'm wondering, would it be clearer to declare a company wide requirement with regard to password theoretical entropy, rather than the usual "at least one big letter, and a small latter, and special ...
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Limiting number of combo attempts with Fail2ban and 128 bits of entropy

Apps such as Fail2ban and DenyHosts enable unix administrators to limit username/password combo attempts to typically 3 attempts. But why 3? Some admins enable more, like 6 or 8 giving honest users a ...
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What affect does modulus have on CSPRNG outputs?

I work in security and I've seen modulus (modulo) used in many encoding and crypto algorithms. However, today, a friend of mine mentioned that using modulo like this: unsigned long int result = ...
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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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Will extra rules to my diceware list generation scheme decrease security?

I finished reading the Code Book by Simon Singh, I'm interested in playing with some of the ideas in the book to help increase my own understanding. I don't intend to implement the following in any ...
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How safe is a password generated from words? [duplicate]

I loathe passwords with completely random letters and digits. It's so much nicer to have a password made up of proper words. Even if the total length is much longer, it's easier to memorize, ...
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Does Docker affect the quality of cryptographic operations?

Is running cryptographic operations (encryption / decryption / signing / verifying / key-exchange / key-generation) in a Docker container affecting the quality of the crypto or entropy? If it does ...
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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 ...
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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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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 ...
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Quantify security strength from entropy and lifetime

Entropy or randomness is a quantitative measure of security strength for various types of passcodes, but in current times with digital technology, breaches, and cracking tools it seems that lifetime ...
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How much entropy does Apple Touch ID sensor read fingerprint has?

Iphone uses by default 6-digit PIN that has an entropy of 19.93 bits When iPhone processes the fingerprint, how much entropy does it have? How long should standard passphrase be until it is as ...
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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 ...
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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 ...
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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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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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How long should zip encryption password be for it take 10 years to crack?

I am using zip 3.0.0 on macOS High Sierra and Ubuntu. Here is my zip version on macOS: $ zip --version | head Copyright (c) 1990-2008 Info-ZIP - Type 'zip "-L"' for software license. This is ...
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Generate cryptographically safe int

How can you generate a cryptographically safe integer that falls within a range in C#? I am trying to satisfy a Veracode issue reporting CWE-331: Insufficient Entropy. Obviously the code below is not ...
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When knowing an individual's plaintext password history, how much information is expected to be gained with a new password? Do we know this?

The premise: Knowing a persons password history should provide information to help when guessing a new password of theirs. At an extreme end, with a password history of wildcats, wildcats1, then ...
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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 ...
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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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256-bit Symmetric Keys As Passwords

Would using a 256-bit binary string, for e.g. ...
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How can ECDSA offer stronger security with the same key length (same amount of entropy)? [duplicate]

It's always been told that ECDSA is more secure "per bit of key size", such that it offers same security with a shorter key, or offers stronger security with the same key length. However, per my ...
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Is Diceware more secure than a long passphrase?

I recently investigated best-practices in regards to passwords, and the overwhelming majority of sources recommended using a password manager. This is great advice, but not usable in every situation. ...
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Length of a stretched gnupg passphrase that is comparable in strength to an unstretched string of 256 random bits

Assume that we want to encrypt a file with gnupg using AES-256 as the encryption algorithm. (Hence, symmetric encryption.) In this mode, gnupg requires a passphrase from the user. I understand that ...
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Hashing password to increase entropy

Is it secure to hash a password before using it in an application to increase password entropy? Does this practice increase entropy when a PBKDF is used in the application itself or does the PBKDF ...
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Impact on required password entropy when introducing two-factor authentication [duplicate]

Is there a best practice or rule of thumb for the impact of introducting two-factor authentication on the required entropy of a used password? Say we consider 80 bits of entropy to be sufficient for ...
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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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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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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 ...
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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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Doesn't the choice of encryption algorithm add entropy by itself?

Let's say someone has my encrypted data and he wants to decrypt it. People always talk about how the length of the key (e.g. 256 bits) decides about the entropy of the encryption, which totally makes ...
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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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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, ...
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Does this attack on RSA keys reveals a major flaw, or this is no big deal with good entropy?

William Kuszmaul published a study of an attack for RSA public keys on his blog https://algorithmsoup.wordpress.com/2019/01/15/breaking-an-unbreakable-code-part-1-the-hack/ The basic idea is, when ...
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How much less secure is a password with a repetitive pattern of characters?

I want to make sure my password is very difficult to bruteforce but also easy to remember and convenient. So my idea is to just use a short password and repeat it a few times like this: ...

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