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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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 ( ...
6
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2answers
278 views

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 ...
75
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12answers
14k views

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 ...
5
votes
5answers
593 views

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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4answers
3k views

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 ...
3
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1answer
43 views

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 ...
1
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0answers
17 views

Evaluating a noise source for a RNG - defining a one-paramter family for RNG [closed]

I am trying to evaluate a noise-source as a means of providing entropy to a random number generator. I am running into trouble when it comes to determining the probability distribution that has the ...
1
vote
1answer
49 views

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 ...
2
votes
3answers
158 views

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 ...
4
votes
1answer
128 views

/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 ...
2
votes
0answers
27 views

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 ...
4
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1answer
84 views

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 ...
6
votes
2answers
466 views

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), ...
2
votes
1answer
97 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 ...
48
votes
10answers
11k views

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 ...
3
votes
0answers
103 views

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 ...
4
votes
2answers
285 views

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 ...
5
votes
1answer
112 views

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 ...
1
vote
1answer
113 views

How to keep a reasonable level of entropy in an encrypted file?

Encrypted (or random) data, by nature exhibit a high entropy value and non unencrypted data will exhibit a low entropy value. From an attacker point of view the precense of this high entropy value in ...
2
votes
3answers
225 views

is it feasible to improve the entropy of XKCD #936 by using a larger dictionary?

XKCD #936 uses a limited subset of the English language, only 2000 words. I just looked it up, and the English language has over a million words, a sizeable subset of those having special characters, ...
4
votes
1answer
220 views

Soundness of GRC.com Haystack padding concept [duplicate]

I was wondering how sound is the concept presented by the Gibson Research Corporation (see below if you do not want to follow the link) about simple passwords (= very easy to remember) with the ...
2
votes
2answers
135 views

How secure is a MD5 hash of an 128bit key

Apparently, for the Android KeyChain an encrypted master key is stored along the MD5 hash of the unencrypted Key. How secure is that? MD5 is known to have collisions, but I guess we can assume with an ...
1
vote
1answer
190 views

Where does /dev/random get its entropy?

I read over and over about how /dev/random gets its entropy from "hardware events." What exactly are these hardware events and how can we be sure that it is random enough?
23
votes
11answers
4k views

One liner to create passwords in linux?

How do you create a readable password using bash with one line? What if i'm looking for 128 bits of entropy? EDIT By readable I mean the 94 printable ascii characters (without space). It can use ...
2
votes
1answer
230 views

How negative are virtual machines (vms) to /dev/urandom?

I looked at the questions here and here. This then piqued my interest as I've recently been involved with looking into FIPS compliance, and in my vm environment /dev/urandom compliance testing ...
2
votes
4answers
541 views

Add a file as entropy source for /dev/random

What I have: A large file containing lots of secret, true-random bytes (yes, I'm sure they're not merely pseudo-random). I'll call it F. What I want to do: Tell Linux that it can use this file as an ...
12
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4answers
3k views

Is an 80 bit password good enough for all practical purposes?

I know that asking how many bits of entropy comprise a strong password is rather like asking the length of a piece of string. But assuming the NSA is not on to you, and that it is hardly worthwhile ...
4
votes
2answers
417 views

Can the human brain generate cryptographically secure random numbers?

A security conscious friend of mine was attempting to generate entropy using random dice rolls to generate a random password, and I became curious about the security of random number generators and ...
0
votes
1answer
230 views

What multiplier to use when calculating the average time to crack passwords with a given entropy?

Suppose that we have a process that generates passwords with entropy E. I'd like to compute the average time it would take for a brute-force attack to crack an MD5-hashed instance of such a password. ...
3
votes
2answers
362 views

Is it really “Time to add a word” if there are no tools to crack passphrases of 3 words and up?

It's "time to add a word" says Arnold Reinhold, the creator of Diceware, in his blog (3/2014). He advices to use 6 word sentences (or 5 words with one extra character chosen and placed at random) from ...
2
votes
1answer
81 views

Usefulness of bcrypt(UUIDv4())

One of my colleagues is working on securing OAuth 2 client IDs and secrets for our OAuth server and he has come up with this scheme where he would not only use UUID v4 to generate random values, but ...
8
votes
2answers
1k views

How can a passphrase with 256 bits of entropy practically be constructed & memorized?

Quoting Wikipedia: A password with, say, 42 bits of strength calculated in this way would be as strong as a string of 42 bits chosen randomly[.] Assuming that interpretation is correct, combined ...
5
votes
1answer
190 views

How many bits of entropy does an identifier contain?

According to https://www.owasp.org/index.php/Insufficient_Session-ID_Length: Assuming that the session identifiers are being generated using a good source of random numbers, we will estimate the ...
3
votes
2answers
169 views

Reliable random seed for RNG

I want to create my computer passwords with a RNG, but I am thinking about one thing: I would use python to write that script and the RNG is controlled by one seed, most likely the time. If I would ...
1
vote
1answer
122 views

Minimum SHA256'd UTF8 encoded passphrase length not stored anywhere

For a passphrase that is UTF8 encoded and then SHA256'd, what is the minimum length to achieve a practically collision free result? The implementation is for a 32 byte cryptocurrency ed25519 seed ...
1
vote
2answers
3k views

How many bits of entropy should I aim at for my password? [closed]

I mainly use 2 passwords: 1 is a 4 word full lowercase passphrase of 18 letters long which I use wherever possible. The other is basically 3 words and a digit with the first word in full uppercase and ...
3
votes
3answers
753 views

How much time / “entropy collected” should generating a RSA 2048bit keypair take?

The purpose of my question is get an better idea about reasonable amout of time the generation of the RSA public/private keypair should take? To be less vague let me specify the question and define I ...
4
votes
2answers
604 views

Credit card number entropy?

I want to confirm that this understanding is correct: A card has 16 digits plus a CV2 The first 6 digits are an issuer identification number The last digit of the 16 is a Luhn mod 10 check digit. ...
2
votes
3answers
443 views

How secure is to seed PRNGs with the sequences from CSPRNG?

Background: Implementing online casino, I would like to use a number of PRNGs with high throughput, like MersenneTwisterFast. I know it is not cryptographically strong, but quite unpredictable when ...
10
votes
1answer
311 views

Where does a Hyper-V guest get its entropy when generating a certificate authority key pair?

According to findings by the EFF's SSL observatory, there are "tens of thousands of keys that offer effectively no security due to weak random number generation algorithm." My understanding of that ...
0
votes
1answer
92 views

How strong is this encryption? [closed]

Given Dictionary containing 1000 three-letter words: dictionary=abc,def,ghi,jkl,mno,pqr... Randomly chosen words from the dictionary: 10-bits-passwords=abc,def,ghi Randomly chosen three words from ...
14
votes
4answers
6k views

Why OpenSSL can't use /dev/random directly?

I couldn't find the answer for the reason anywhere, even the wiki page doesn't explain it. This seems like using a PRNG for seeding an another PRNG. The first one (/dev/random) may itself be seeded by ...
-1
votes
1answer
144 views

physical access proof smart card for disk encryption [closed]

Current full disk encryption on mobile devices rely on low entropy passwords like PIN numbers or pattern locks. Being able to use a smartcard with such mobile devices is a tempting idea. I know that ...
3
votes
2answers
981 views

How to generate cryptographically strong pseudorandom data very rapidly?

What's the best way to go about generating a fast stream of cryptographically strong pseudorandom data without installing uncommon packages? Drawing from /dev/urandom is far too slow. I had an idea ...
4
votes
2answers
438 views

How can you securely generate keys on AWS?

Our application needs to generate secure keys for long term storage on AWS using openssl. But I've seen some instance where entropy falls dangerously low on AWS machines and this doesn't appear to be ...
2
votes
0answers
145 views

Passphrase generator and strength & recovery time estimator. Right strength and randomness?

Questions about the strength of pass phrases frequently popup, as does: how to generate a strong passphrase? I tried to combine both in a tool. The free tool also includes recovery time estimations ...
4
votes
1answer
716 views

Open-source alternative for CryptGenRandom?

Let's say that for some reason I don't trust CryptGenRandom. Are there any open source software Windows entropy collectors to get cryptographically secure random numbers from for seeding purposes? ...
0
votes
1answer
3k views

Why is /dev/random so slow on Linux? [duplicate]

If it's true you only need about 128 bits of entropy to fuel enough data forever, why is it that /dev/random is so slow? My system has uptime of 214 days! Is it really only gathering .000000001 bits ...
5
votes
2answers
2k views

How can I measure (and increase) entropy on Mac OS X?

I'd like to generate a bunch of keys for long term storage on my MacBook. What's a good way to: measure the amount of entropy and ensure it is sufficient before each key is generated, and ...
12
votes
3answers
3k views

Java SecureRandom doesn't block? How?

I know from experience that reading from /dev/random blocks when the Linux kernel entropy pool runs out of entropy. Also, I've seen many articles and blog entries stating that when running on Linux, ...