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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412 views

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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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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1answer
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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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1answer
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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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1answer
48 views

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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1answer
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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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1answer
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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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837 views

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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1answer
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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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1answer
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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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1answer
258 views

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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1answer
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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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1answer
232 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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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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1answer
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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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1answer
573 views

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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1answer
290 views

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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1answer
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Password entropy boosting [closed]

Can the process of generating a password based on the transformation of random 3D data into a 2D data chain have better entropy than other methods of generating 2D random data chains?
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1answer
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Passphrase vs. password entropy

For a while now I have been interested in the passphrase concept as a potentially more secure replacement for classical passwords. My interest stemmed from a gut feeling that passphrases would be of a ...
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2answers
441 views

Entropy on native memorable password on macosX keychain

I have been trying to find information on this. But I haven't found anything online. When you use the password manager on mac, it can provide "memorable" passwords. For example pick3"enigma. (You ...
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1answer
232 views

Are encrypted files safe in Windows 10 when using PINs?

In Secrets and Lies, Bruce Schneier writes: Many keys are generated from passwords or passphrases. A system that accepts 10-character ASCII passwords might require 80 bits to represent, but has ...
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multiple dice ware lists to make memorable passphrases?

I understand the basics of why diceware produces good security and why seven word passphrases are a good idea these days. The EFF has helpfully produced updated diceware lists that eliminate lots of ...
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How was the concept of password entropy developed?

I understand how to calculate password entropy and what the Length and Character values represent. I also have a reasonable understanding of other types of entropy (e.g. Shannon). However, password ...
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2answers
269 views

Check the “security” of a password [closed]

I'm trying to find a tool to validate the security of a password and I've come across cracklib or libcrack2 (on Debian), which seems to be used a lot for the task and appears to do exactly what I ...
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1answer
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Approximately how much entropy in each of these low entropy sources?

We need a lot of entropy. Let's be a little unrealistic and assume that we don't have access to entropy pools like dev/random, and must do all the entropy collection ourselves. The program is running ...
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2answers
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On an embedded system with no external input, can haveged provide entropy?

Take an example embedded system: Microprocessor Flash memory SDRAM There is no UI and no network connection. Can the CPU timing jitter that is used by haveged provide adequate true entropy to seed /...
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1answer
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How to determine how entropy changes when using uppercase, numbers and special characters in a dictionary based passphrase?

I know the general math behind using character-based and dictionary-based passwords/passphrases and how to determine the entropy of the result. But I am unclear how adding uppercase letters, numbers ...
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Expert quote on entropy for uncrackable password

Could anyone point to a quote in a published work - or suggest a recognised expert who might provide a quote - which answers the following question How much entropy in a password would guarantee ...
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2answers
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How does the password Tr0ub4dor&3 have ~28 bits of entropy? [duplicate]

I rencently seen this : I can't figure out, how he computes 28 bits of entropy for a password like "Tr0ub4dor&3" seems really few...
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2answers
216 views

Research about entropy of human randomness?

An argument people often use in favor of password managers is: Human-generated passwords have less entropy than randomly generated ones! Is there any research to back this up? Can we quantify it? ...
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4answers
822 views

Should I vary the length of my completely-random passwords for the best security?

I use LastPass comprehensively, and for each new site/password I almost always have it generate a random password of the same number of characters, allowing letters, numbers, and symbols (except when ...
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1answer
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Should Longer Random Data Have More or Less Entropy?

I have been making a random number generator using an Arudino's analog pins, bitwise shifts, and XOR. I have been using the Unix command 'ent' to measure my entropy. I have tested different sizes of ...