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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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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GPG keys generated with diceware entropy?

Considering the absolutely critical role that entropy plays in the generation of keys, I am wondering if there is an easy way to use diceware (true random numbers) to generate an OpenPGP key with ...
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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 Debian. Here is my zip version on macOS: $ zip --version | head Copyright (c) 1990-2008 Info-ZIP - Type 'zip "-L"' for software license. This is Zip 3.0 (...
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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 character, get ...
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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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Effects of new random Session token for each HTTP Request

On successful authentcation, a web application issues a session cookie that is a constant length string of apparently random hex characters. ...
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Is it possible to bruteforce a file encrypted with a keyfile?

If someone used a keyfile (4092 bit of entropy) to encrypt a file, and bruteforced it with Hashcat... would Hashcat have to guess the blob data in the keyfile to crack the encrypted file? $ dd if=/...
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rng-tools entropy sources

Using rng-tools 6.3.1, I list the entropy sources: $ rngd -l Entropy sources that are available but disabled 4: NIST Network Entropy Beacon Available and enabled entropy sources: 2: Intel RDRAND ...
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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 ...
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Chrome generated passwords not high entropy?

On Chrome, if you open a sign up page, it will offer to fill and remember the password field. I did this and got the following sequence of passwords offered as generated: suCipAytAyswed0 ...
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Why would Bill Burr of NIST say N3v$r M1^d?

Wall Street Journal wrote that Bill regrets his password recommendations NIST SP 800-63 Appendix A. Apprendix A is titled "Estimating Password Entropy and Strength". It is about how we might assess ...
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How can an Android device be unlocked, and how long would that take?

The original question was about the minimum password (or PIN) length (or entropy) for the screen lock in Android. Seeing that nobody answered, and following Schroeder's advice, I'm going to edit it ...
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Calculating Entropy using md5sum, sha256sum etc

We can calculate the Entropy S of a string simply like this: S = L * log_2(N) Where L stands for used characters in the string And N for every possible character Example: We want to calculate the ...
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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?
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How much entropy is required for a Grid Card?

We're in the process of implementing multifactor authentification. One good candidate for this was the "Grid Card" - a small table with random letters and digits. Upon login, the user would be queried ...
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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 ...
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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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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 ...
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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 ...
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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). ...
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How to convert zxcvbn entropy to score

I want to use zxcvbn-c but it gives the entropy number, not score like the javascript library does. How do I convert entropy number to a score? (0 to 4) The zxcvbn blog/source mentions that the score ...
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What is the benefit with passwords that are always 50% numbers and 50% letters?

In Teamviewer, I am using "secure (8 characters)" passwords that are changed daily. I noticed that the password is always 4 numbers and 4 lower case letters, with random positions. I might be naive, ...

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