The generation of random or pseudorandom data, and the use of randomness in security protocols

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How to predict C rand()? [duplicate]

Is there a practical way to predict previous/next C rand() output if i have some of the values? How many values do i need? Do they need to be consequent? If it depends on compiler - for which ...
8
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3answers
759 views

Generating random passwords by clicking randomly on the keyboard?

How secure is it to generate random strings/passwords manually for different purposes by just clicking randomly on the keyboard ? I usually need random strings for salts and for passwords, and I ...
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597 views

How to generate a highly unpredictable random bytes

void vncRandomBytes(unsigned char *bytes) { int i; unsigned int seed = (unsigned int) time(0) + getpid() + rand(); srand(seed); for (i = 0; i < CHALLENGESIZE; i++) { bytes[i] = (unsigned ...
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1answer
153 views

Detecting PRNG Use from Output

Question: Is there a way to detect the use of a PRNG strictly from observing the output provided by an application? Background: During an audit of a key generating algorithm that I knew was based on ...
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3answers
888 views

CSRF Countermeasures

I'm working through a book on web application security and it says that an effective CSRF countermeasure is to assign a temporary pseudo-random token to sensitive actions performed by authenticated ...
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2answers
600 views

Filling the disk with random data prior to encryption?

Filling the disk with random data prior to encrypting it will supposedly make it harder for the attacker to perform any cryptanalysis. Most sources seem to state this is because it will be harder for ...
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2answers
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should i use urandom or openssl_random_pseudo_bytes?

I am developing a site in php 5.4 and i was wondering which is better to use to gen a random salt for password security? $salt = sha1(openssl_random_pseudo_bytes(23)); or $seed = ''; $a = ...
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2answers
606 views

How is the available entropy in /dev/random calculated (or estimated)?

It seems (to a non-expert) that /dev/random is acclaimed to be useable as a source of pure random data. However, I am curious as to the analysis of the file /dev/random. /dev/random is a collection ...
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3answers
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Is a predictable MAC address a risk?

If you knew from the public internet that a certain IP address belonged to a machine with a certain MAC address, can you see any security exposure associated with that? I know that some software will ...
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Do the popular smartphone operating system have a cryptographically secure random source? [duplicate]

Possible Duplicate: Do mobile OS’s provide crypto-quality randomness? Linux and Mac OS X has /dev/urandom, Windows has CryptGenRandom. Do iOS and Android have a similar way to generate ...
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5answers
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create a variants of MD5

I have also asked similar q here : To create a variants of MD5, I made following changes : MD5 uses a non-linear sin(i)* pow(2,32) ----> i plane to use cos(i)*pow(2,32) Instead ...
4
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1answer
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Computational Feasibility of finding 'Good Links' of the following format

I recently stumbled upon this and am checking here to see if what I am proposing is indeed feasible and can be considered a breach of privacy. For obvious reasons I am not revealing the website ...
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Generate cryptographically strong pseudorandom numbers in Javascript?

Is there any good way to generate cryptographically strong pseudorandom (or true random) numbers in Javascript? The crucial requirement: if a.com's Javascript generates some random numbers, no one ...
3
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4answers
630 views

SMS Authentication: random OTP or a cryptographic one

I'm adding two-factor authentication using SMS to enhance an existing login process. Since I'm not working with physical tokens, I was wondering what is considered the safest: Sending random 8 ...
3
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3answers
314 views

PRNG: Does combining insecure algos help?

Reading about how insecure PHP's rand function is, I was wondering if it helps to combine random functions. The suggested function there, openssl_random_pseudo_bytes, can also be cryptographically ...
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3answers
2k views

How insecure are PHP's rand functions?

There are some pseudo-random-number generators in PHP: rand(), srand(), mt_rand(), mt_srand(). You can look at their code here. I understand those functions are insecure, but how insecure are they? ...
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4answers
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How insecure are non-cryptographic random number generators?

I always hear that C rand() is not secure, but what how many calls would you need to know in order to predict the next value (or at least cut down the possibilities)? Would they have to be sequential? ...
20
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5answers
766 views

Hashed password storage with random salt

Ever since I've been making sites that require a user to log in with a username and password I've always kept the passwords somewhat secure by storing them in my database hashed with a salt phrase. ...
9
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2answers
541 views

Can I use hardware random number generation on my computer? Am I already using it?

A lot of computer security depends on encryption: SSL connections, TCP packet sequencing, encrypted files, etc. These depend on random number generation to ensure that attackers can't guess the ...
8
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1answer
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How to select /dev/random or dev/urandom in the code in Android?

When generating randomness using SecureRandom in Android, I want to select /dev/random or /dev/urandom as the seed source. It can be done in java.security file on Linux and Windows systems but there's ...
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4answers
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What do I need to configure, to make sure my software uses /dev/urandom?

When setting up a server, what configuration changes do I need to make sure that all of the software uses /dev/urandom instead of /dev/random? Some servers don't have much entropy in the entropy pool ...
3
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1answer
924 views

Requirements for a secure session id?

I'm writing a web service which stores data which will be shared between two separate systems. /session/requestNewSession?args=<data> => returns session id ...
4
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3answers
791 views

Pseudo Random Generator is not initialized from the (entropy pool)?

The RHEL5 manuals state that /dev/urandom will use the entropy pool until it's exhausted, and then it will resort to a fall-back pseudo-random algorithm, so that it will never block. But when ...
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1answer
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What are the requirements for a random number generator to a be safe to use in cryptography?

When I look at most RNG's (random number generators), I see a disclaimer that looks similar to this: Caution: Mersenne Twister is basically for Monte-Carlo simulations - it is not ...
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2answers
286 views

What are the pitfalls while generating a random number from a random data set?

I am relatively new to the GPG key system and I have been been learning about the system through experimentation. I now know that while generating a random seed for the key generation, the random ...
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4answers
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pesudo random password

I post a question before about one password repeating to make it longer, now its a new way want to ask about, if take the word 'secure' and instead of repeating it put somenumbers between it, exp: ...
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2answers
188 views

What to consider when generating random code as part of two-factor authentication?

I want to write a patch for a two factor authentication system that someone else has started. The code is a module for a PHP content management system and sends an SMS message to a user's phone, after ...
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4answers
5k views

What are you doing when you move your mouse randomly during a truecrypt volume creation?

Is that called a 'round' every time you move your mouse when creating a new volume? I'm talking about the screen with the random numbers during the volume creation process. What is the purpose of ...
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2answers
205 views

What factors increase the probability of duplicating a GUID?

It's been argued that a GUID doesn't do a good job of being a one time security token , and it makes sense because GUIDs aren't random. In my scenario: suppose a given company is using GUIDs as a ...
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2answers
5k views

Can the numbers on RSA SecurID tokens be predicted?

My workplace uses these SecurID tokens which provide you with a temporary password, the code will expire after a short time. I have always been fascinated by the things, because it seems as though ...
5
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1answer
541 views

Should I include a random padding in every HTTPS request and response?

According to the following paper, it is possible to decrypt HTTPS traffic by inspecting AJAX calls and using the size parameter as a cryptographic oracle. Should I be sending a variable length ...
4
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1answer
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OpenSSL RAND_poll 'good enough'

We are using OpenSSL for generating IV's and other random data. We initialize it using RAND_poll and, on Windows, RAND_screen. The question is though, if the seed generated by those methods is good ...
4
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1answer
251 views

Random number for HTTPS Message Authentication Code (MAC)

Recently I found that Netscape used quite simple algorithm to generate random number for Message Authentication Code to establish an HTTPS connection (Netscape used time, process identification ...
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3answers
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Cryptographic Security of Dynamically Generated, Non-Random Salts

So when it comes to security, when I have an idea that seems good, but no one else seems to be doing, I try to assume that I'm overlooking something obvious or otherwise significant. This is one such ...
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2answers
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/dev/random security holes

I'm doing some reading into the security issues surrounding /dev/random but it's proving to be hard to find good sources of information. Can anybody help? I've asked Google and got a bunch of articles ...
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2answers
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Flaw in encryption through pseudorandom number stream (from gpg documentation)

I was reading PGP docs and came upon a part written by Phil Zimmermann (PGP's creator) that piqued my curiosity: When I was in college in the early 70s, I devised what I believed was a brilliant ...
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Should passwords be truly random?

When generating a password, should it be "truly random" or should I make it a little less random by enforcing some rules? If a password is generated at random, it could come out all-lowercase letters ...
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2answers
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Is this algorithm for a random string cryptographically secure?

I've pieced together this algorithm (if it can be called that) from various bits of code I've seen online, and I'm wondering how cryptographically secure it is. It's used to generate passwords: ...
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2answers
3k views

Is “real salt” the same as “initialization vectors”?

In the question about real vs. fake salt, the answers describe how real salt 'perturbs the encryption algorithm.' I know roughly how initialization vectors work; is this the same concept, or something ...
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1answer
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Asynchonous Linear Feedback Shift Register : test vectors

Well I've been working on coding LFSR structures for my research projects. Being able to find sources on the subject, I've been able to test a single LFSR with different initialisation and TAP ...
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2answers
532 views

Is a rand from glibc's rand secure for a login key?

Same question as Is a rand from /dev/urandom secure for a login key, but with glibc's rand function instead of /dev/urandom. And what would be a sufficiently secure seed generator?
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4answers
1k views

Using computer random number generators to produce keys, it is secure?

Does generating an encryption key using the random number generator on one's computer present a security risk? If so how might that risk be mitigated, specifically when generating RSA key pairs in ...
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2answers
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Cracking a linear congruential generator

I was recently listening to the security now podcast, and they mentioned in passing that the linear congrunential generator (LCG) is trivial to crack. I use the LCG in a first year stats computing ...
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3answers
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Is a rand from /dev/urandom secure for a login key?

Lets say I want to create a cookie for a user. Would simply generating a 1024 bit string by using /dev/urandom, and checking if it already exists (looping until I get a unique one) suffice? Or should ...
8
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1answer
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Howto seed the PRNG in OpenSSL properly?

I am creating an application which runs on a mobile node with Ubuntu, which does not generate enough entropy bytes to the /dev/random, and does not always stay connected on the Internet to use typical ...
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2answers
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Evaluating the entropy gathering in a PRNG

I'm reviewing the random number generator (expected to be of cryptographic quality) on an embedded device. My point of view here is the operating system and crypto library implementer. I'm ...
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4answers
8k views

License key / Serial number generator and checker

I need a serial number generator and accompanying checker. I would like to be able to set a salt (and maybe a length). The generator should only produce serial numbers that pass the test of the ...
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5answers
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Do mobile OS's provide crypto-quality randomness?

Which mobile OS's provide a primitive to generate crypto-quality randomness that applications can use? On desktop systems, these features are pervasive. Unix provides /dev/urandom. Windows provides ...
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3answers
4k views

How long should a random nonce be?

NIST provides good guidelines on the length of keys and hashes for various algorithms. But I don't see anything specifically on the length of a random or pseudo-random nonce (number used once). If ...
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Are GUIDs safe for one-time tokens?

I see a lot of sites use GUIDs for password resets, unsubscribe requests and other forms of unique identification. Presumably they are appealing because they are easy to generate, unique, ...