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 ...

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Why doesn't the number of bytes required by GnuPG generating the key decrease?

I ran a gpg --gen-key on a remote machine connected with SSH and left it to do its job. It finished successfully, however during the execution time it asked to perform random actions to collect more ...
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Convert SHA-256 to SHA-1 and MD5 - Increase bit length/entropy?

I know this is a real dumb question and I am certainly talking complete rubbish, but let me explain: We have a long SHA-256 hash, e.g.: ...
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HPET effects on CSPRNG for Linux OS

HPET or High Precision Event Timer is a hardware built-in clock source available in most processors. I would use the computer to generate CSPRNG and do cryptographic operations. My question is: Is ...
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Would a Password Using All Possible Unicode Code Points Cause Problems in Traditional Hashing Algorithms, such as Bcrypt?

I've been toying around with this idea, but hypothetically, if you had a password manager that would use any possible renderable (e.g. not control characters such as BEL, NUL, DEL, etc., or surrogate ...
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Is it better to choose less-vulnerable random password?

I have created a random password generator function (which can be found here if anyone wants a look), which will churn out passwords with a random mix of letters, numbers, and other characters. This ...
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What are possible methods for calculating password entropy?

I noticed there are tons of questions and answers about password entropy on this forum, some even suggesting formulas for calculating it. None did answer my exact question. What are possible or ...
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What's eating my entropy? Or what does entropy_avail really show?

Below are graphs with the value of /proc/sys/kernel/random/entropy_avail on a Raspberry Pi. This answer which might not be correct describes it as: The pattern always comes to the same "stable" saw ...
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Why are low-entropy passwords considered OK in many cases?

When talking symmetric encryption, a 56 bit key is known to be so weak. If you use it for your encryption, you are considered a goner as you wont survive brute-force. When talking passwords however, ...
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How secure are these password schemes?

On One liner to create passwords in linux?, I see advice generally of the form head -c16 /dev/urandom | md5sum. They're all random combinations of text manipulation commands, sha1, base64 and md5sum ...
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philosophical: restricting the password space increases security

This is more of a philosophical question. Suppose that you are trying to choose a good password for a particular online service, say your bank's e-banking service. Now the bank has some restrictions ...
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How fast is it to bruteforce a 48-bit key with current technology?

Say you have a truly random hexadecimal key formatted as 1234.5678.ABCD, with 48-bit entropy. Assuming the key is stored with no hashing/salting, how fast/easy would it be to brute force it with ...
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Entropy in Address Randomization

I am trying to understand the concept behind address randomization (ASLR). I'm reading the related wikipedia article which states: Security is increased by increasing the search space. Thus, ...
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Can I generate a random 32 bit key by using the Java hashCode and random English words?

I want to generate and communicate a 32 bit key to Bob over a phone conversation. I know he happens to have the same Java and OS installed as I have. Suppose I have a dictionary of 100,000 (English) ...
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Would a multilingual Diceware password be more secure than a monolingual one? [duplicate]

I've been reading up on Diceware recently, and I'm wondering if using a mix of languages would make it even more secure. On the face of it, it would force a potential attacker to consider an even ...
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Why do Google 2-factor authentication SMS codes never start with a 0? [closed]

When you use 2-step authentication to log to your Google Account, you can get an SMS on your mobile-phone with a G-123456 style code. I think that I never got a code with a leading zero. Is there a ...
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Is there a threshold of bits of entropy below which hashing becomes meaningless?

I just read a help page by a mail provider in which they state that all mobile phone numbers will be stored as a salted hash. This strikes me as interesting, since phone numbers don't contain a lot ...
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Does eliminating the possibility of repeat words make Diceware passwords significantly less secure?

I read about Diceware passphrases and whipped up a little program to generate passwords in that style. I do this by taking the list of dictionary words to create passwords and "ordering them" by a ...
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273 views

With openssl des3, what are the passphrase parameters?

I'm using OpenSSL's des3 tool to encrypt a file, e.g. openssl des3 -salt -k SUPER_SECURE_PASSPHRASE < inputFile > outputFile Everything's working, but now I have to choose a final, fixed ...
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Is there any practical weakness to using MT19937 to generate passphrases?

Suppose I use MT19937 to choose random words out of (say) the Diceware word list. I know MT19937 is not considered a cryptographically secure PRNG, but Wikipedia suggests the weakness is rather ...
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Strength of variable-length generated password

I am contributing to the Word Sequencer plugin for KeePass password manager, which can generate diceware-style passwords using a high-quality PRNG. Something in particular I'm working on is estimating ...
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How much entropy should passphrases for encrypting ssh keys have?

When one generates keys using ssh-keygen one gets prompted for a passphrase to encrypt the generated key with. How strong should such a passphrase be, entropywise, to withstand a full-blown brute-...
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55 views

Securing a Secure Entropy Service

Many moons ago, I answered a question about Java blocking due to a lack of entropy in /dev/random. (http://security.stackexchange.com/a/53025/41709) My main suggestion was to use /dev/urandom, but I ...
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Resetting the Windows RNG

According to this research, Windows seems to produce the same sequence of random numbers indefinitely when a process is kicked off before a VM snapshot is taken. This is a huge issue obviously when ...
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Does using NATO's phonetic alphabet increase password strength?

Given an alphanumeric password intended to be strong yet easy to remember, we change each alphabetic character by its NATO alphabet counterpart (e.g. 'cat' becomes 'charliealphatango'). I understand ...
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What would typically be considered an acceptable string entropy for passwords?

I have gained interest in creating a way to check password strength (think password strength meters - yes - another one). I've found many ways to award a score on a policy driven approach (one capital,...
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Password security and entropy - degeneracy question

I have written a short password generator which uses a mixture of words from a dictionary and randomly generated passwords, and I'm wondering if I did the entropy calculations correctly. Usually I use ...
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330 views

Do you need more then 128bit entropy

UUID use 128 bit numbers. Currently it is not feasible to randomly produce two UUIDs that are the same. Does that means 128 bits of entropy is suitable for all cryptographic operations? I would ...
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191 views

What is the entropy of a password made with pwgen?

pwgen is a unix utility that generates "memorable" passwords randomly. The man page says the entropy is lower than truly random passwords with the same specification. What is the actual entropy of a ...
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Entropy on payload

How can I guess if a payload is obfuscated or encrypted? in other words can I apply Shannon Entropy algorithm to a binary payload? any advice will be appreciated, thanks in advance
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How much stronger does a paragraph/sentence based password becomes with random characters added?

I was reading some questions on here regarding the correct horse battery staple method, and the conclusion was that, assuming any words in the list of most common English words, every word adds about ...
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183 views

Does manipulating a random password significantly reduce its entropy?

Suppose I generate a password using a secure random number generator and all the available character classes. For example, c.hK=~}~$Nc!]vFp9CgE. Consider that this password may need to be used in an ...
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Password: ham,ham,ham,bacon,bacon,ham

Why do we bother with dice ware? Is rolling dice and looking up in a printed book (or using a digital analogue) a string of N random words any more secure than simply repeating a word or two N times? ...
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A simple question about entropy and random data

Let's say I roll a 6-sided die 100 times and record the results into a 100 character string, for example: //this is obviously an example (and very unlikely) outcome "...
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Which format of secret would be the most efficient for human memory? [closed]

I am talking about something-you-know identification factor. Examples of those formats are passwords, passphrases, pin-s, picture passwords ( http://blogs.msdn.com/b/b8/archive/2011/12/16/signing-in-...
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How much entropy is good enough for seeding a CSPRNG?

I have some fundamental questions on using Cryptographically Secure Pseudorandom Number Generators (CSPRNGs). What should be the size of the seed that I initialize a CSPRNG with? How often should I ...
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Password rules: Should I disallow “leetspeak” dictionary passwords like XKCD's Tr0ub4dor&3

TLDR: We already require two-factor authentication for some users. I'm hashing, salting, and doing things to encourage long passphrases. I'm not interested in the merits of password complexity rules ...
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How much is the entropy of a randomly generated password reduced if I regenerate until I get a password I like? [duplicate]

In many of the answers and comments on the well-known XKCD #936: Short complex password, or long dictionary passphrase? question, the importance was stressed of generating the password randomly, and ...
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How secure is Snowden's MargaretThatcheris110%SEXY password?

In an extra from Edward Snowden's interview with John Oliver, Snowdon advises that a good password to use is one such as MargaretThatcheris110%SEXY.. Also, on the Errata Security blog, Robert Graham ...
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output from CryptGenRandom [closed]

Can we capture the output of Windows CryptGenRandom function. Suppose an application is utilizing CryptGenRandom, as a user can we know what is the Random Number generated and given to the ...
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How to check randomness of a hash?

I have a REST api in which the server allots a unique token each time a user is logged in. Its a hash containing numbers,letters and a one or two special chars. I want to check the entropy of these ...
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How secure are “pattern” passwords?

I was watching a TED Talk about password security recently which covers quite a few different types of passwords and compares how secure they are and how easy they can be remembered. One type of ...
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/dev/random in EC2 cloud

is /dev/random any good in AWS EC2 for use in making a shared key that will be passed over a secure channel? i am concerned that a launched instance would have not much entropy to begin with. what ...
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General Entropy as opposed to Password Entropy [duplicate]

I know that the formula for the entropy of a message is: (I believe b can be set to 2) but when calculating the entropy of a password websites usually only compute log2(p-1), ignoring the first term....
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VM production server and low entropy

I'm monitoring a VM functioning as our production server. I noticed it has at many times, quite low entropy (/proc/sys/kernel/random/entropy_avail). On average our server(which among other stuff does ...
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Linux kernel entropy - does it matter to /dev/urandom and what is a minimum?

This question had been asked several times, but still something's not clearly understood from other answers I have a few servers running with a custom built linux kernel (minimal driver modules etc), ...
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142 views

Evaluating the Entropy of the PRNG in OpenSSL

I've have a question on the PRNG in OpenSSL. I would like to understand how do you evaluate the diversity/entropy of the PRNG used in the OpenSSL (Cryptographic Library). If this is the wrong forum,...
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Why does the user pick the password?

Almost every web service I can imagine has the user pick the password. Why is this? Couldn't the system choose a better password? It doesn't have to be some complicated mess; see http://security....
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What is the most efficient password scheme in terms of entropy per convenience [closed]

Although the main points are right, but now six words are needed, which is both inconvenient to remember, and inconvenient to type. My question is, has then been any case studies on the most ...
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Password strength metrics

In the question Source code as password I suggested using a combination of entropy and as @Lawtonfogle put it 'meatspace difficulty'. As suggested in the xkcd comic correct staple horse battery is a ...
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Random padding in hash functions

In this answer, it was recommended that you add random padding when hashing messages for a trusted timestamp, such as for predictions, in order to avoid dictionary and brute force attacks (at least ...