Questions tagged [random]

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

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4
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1answer
344 views

Is there a PRNG in Java with a period of at least 256 bits?

From what I can tell, Sun JRE/JDK's are limited to only providing 128-bit strong cryptography without downloading an unlimited strength jurisdiction policy files. My question is, if I install theses ...
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1answer
57 views

Best practice for serving sensitive data?

Our invoice vendor serves invoice images via http and does not require any type of authentication. EX: http://example.com/companyid/image.php?id=Lhjjfkedhf_739567395 Using HTTPS would be a good ...
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1answer
830 views

Is reseeding OpenSSL CSPRNG necessary if using RAND_bytes?

I read that cryprographic secure PRNG (CSPRNG) need a random seed to provide random output. Looking at OpenSSL that seems to be archived by RAND_poll() and random data is fetched with RAND_bytes(buf, ...
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1answer
82 views

Creating secure random output that is repeatable across machines [duplicate]

I'm having trouble figuring out a solution to this problem. Basically what i am trying to do is create random data that can be repeated across multiple machines by a user but is also secure from ...
3
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2answers
114 views

Securely generate a rng seed using a small number

I'm trying to figure out a secure method to generate a rng seed to a rng using a small pin number that is 5 digits. The issue that i can see with this is an attacker could very easily just loop ...
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3answers
540 views

Access Key In URL - Securing The Unsecured!

I'm having some difficulties doing this the right way (as much as it can go). Some time ago, I've asked a question here, asking for help on how to implement sending an access link through email. ...
0
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1answer
290 views

Which ciphers produce random cipher text?

I already know AES produces a "random" output. 5e4e6440826d6afc4535fbf078455f791159701a9df624ddd4e4dda84523b6a7 Its cipher-text doesn't follow a pattern and is indistinguishable from noise. Is ...
3
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1answer
239 views

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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1answer
1k views

What is the purpose of including time as a part of random in TLS Client & Server Hello messages? [duplicate]

RFC 5246 Section 7.4.1.2 states that the 32 bytes of random required in the Client and Server Hello messages should be 4 bytes of time and 28 bytes of random. Why can't it be 32 bytes of random? ...
8
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1answer
891 views

Random string vs hash(random string)?

I'm implementing a one-time token service. Each of these one-time token represents some server side data/action associated with it (a 'email confirm' action for example), so that my web service can ...
3
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1answer
248 views

What are the problems of using OTP encryption with TRNG?

I've programmed a simple One-Time Pad "encryptor" that can merge two files into one by using bitwise XOR. The pseudo-random key files are generated by using the CryptGenRandom() function from ...
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1answer
6k views

Is keepass random password generator fully secure and trustworthy?

Am I safe using keepass for generating passwords? For example my accounts, am I safe using a keepass generated password? Could my future keepass master-keys be safely generated in keepass? What method ...
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0answers
189 views

Token-based authentication for specific requirement

We have the following requirement for creating a token in .NET to be used in providing a challenge token and an actual authentication (auth) token. The auth token will then be used to authenticated ...
4
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2answers
174 views

Is there a benefit in measuring randomness? How would it be done?

Is there any benefit in determining how random a given file, stream, signal is? I guess this would be useful to determine If something is (poorly) encrypted To verify the proper encryption of a file,...
2
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2answers
167 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. (https://security.stackexchange.com/a/53025/41709) My main suggestion was to use /dev/urandom, but I ...
5
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1answer
381 views

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 ...
3
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1answer
167 views

Skewed Randomness

According to random.org, Any source of true randomness may contain skew towards 0 or 1 in the data I am a bit confused about what this exactly means and why this "skew" is present in all "true ...
5
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2answers
1k views

Two ways of generating the IV

I'm looking at some code, and in a particular scenario, the code would need to generate two IVs. The second IV-generating code simply uses the C# Rijndael GenerateIV() The first IV-generating code ...
3
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1answer
222 views

Defeating ROP attacks in x86

Most defense techniques against ROP revolves around randomization, such as ASLR. If I mark all regions of memory, other than the code segment, non-executable, will this defeat ROP?
4
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1answer
507 views

OpenSSL 0.9.6a PRNG algorithm weakness: How to exploit?

I saw an OpenSSL security advisory for Openssl 0.9.6a Recently a cryptographic flaw in OpenSSL's built-in pseudo-random number generator (PRNG) was pointed out to us by Markku-Juhani O. Saarinen , ...
3
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1answer
263 views

Can a smartphone’s accelerometer data be used for implementing a TRNG?

I'm trying to generate a true random number from smartphone's accelerometer, then pass it as a seed to a CSPRNG to generate true random numbers. I know that a lot of people tried it and the ...
3
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1answer
262 views

Is Jericho Comms TRNG reliable?

I'm looking for a method to generate true random bits/numbers on smartphones. Create a custom TRNG seems to be tricky and a lot of people suggest to trust in already existing ones, widely tested and ...
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3answers
14k views

Can I rely on openssl_random_pseudo_bytes() being very random in PHP?

I came across an application which needs to generate a random token for each user. It is very important that each generated token is unique. Application code was as follows: $token = md5(...
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2answers
396 views

Does adding a random character to a pseudo-randomly generated password improve entropy significantly?

I'm asking a practical question. I was taught computers are bad at generating random data. Does this mean password generators, such as the one built into Keepass, suck? If yes, then would it help for ...
3
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1answer
3k views

Correct way to generate password salts in PHP 5.3 on Linux given my constraints?

In examining our database storage of hashed passwords with salts, I note a high rate of salt collisions, i.e., there are far too many cases where two table rows have the same salt stored. One ...
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1answer
146 views

Hacking bad people to help a good cause [closed]

I want to hire a hacker to get emails by and between 2 people I think are participating in something unethical. It is very important that I not break any laws. A review of this site makes it appear "...
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2answers
189 views

Is a random work factor an increase or decrease of security?

Assume you use a proven hashing algorithm, like bcrypt with a work factor of 10 or PBKDF2 with 10K iterations. Normally that's really secure already and would give enough security already for most ...
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2answers
644 views

A “hardware” random number generator for mobile phone

I have been trying to write a random number generator using the hardware of the phone. After reading other people's attempts and tried some. I came up with the following to generate the seed: Play a ...
4
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1answer
162 views

Is encrypted data a good random source?

Given that someone needs my encryption key to predict the output, can I encrypt arbitrary data (zeroes, system logs, personal photos) with AES and a secure passphrase, and use the result as a RSA/SSH/...
4
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2answers
406 views

Is it secure to create a Bitcoin address from a private key generated by Rand() instead of cryptographic elliptic curve

I am writing a C++ application that creates a Bitcoin address. I am having a hard time installing openssl for windows and making it work for visual studio. So, I am asking myself, if I create a ...
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3answers
1k views

Is it worth augmenting /dev/random entropy in software?

Modern Linux systems, especially headless virtuals, often have shallow /dev/random entropy pools, which can cause software to block or fail to run (e.g. Tripwire in FIPS mode) While many agree /dev/...
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1answer
310 views

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 "...
4
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2answers
2k views

Why does gpg use /dev/urandom [duplicate]

Looking at the strace output of GPG on my box seems to show that it uses /dev/urandom when encrypting a message without any access to /dev/random even when --no-random-seed-file is specified. Are ...
9
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1answer
2k views

Attacks on keys generated with low entropy

If I were to give someone a two 4096 bits keys, and say one was generated in a Linux OS with very very low entropy available, and one was generated in a Linux OS with more than enough entropy. Would ...
7
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2answers
1k 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 ...
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3answers
5k views

Token-based authentication - what's a good token length?

What's a good token character length for a token-based login? Currently I'm using the following code: <?php $token = bin2hex(openssl_random_pseudo_bytes(16)); Is 16 sufficient or should I ...
3
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1answer
290 views

Law of Large Numbers vs. OpenSSL RAND_bytes

I have a system where tens of thousands of users log in whenever they like and my server has to assign them to one of many databases. I would like to distribute the users evenly amongst the databases. ...
16
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1answer
3k views

Is Postgres's uuid_generate_v4 securely random?

I'm using Postgres's uuid_generate_v4 in a uuid primary key column to generate secure one-time authentication tokens. Is this okay? Does Postgres use a secure random number source for generating these ...
3
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2answers
2k views

Calculating the time required to brute force a random code

Say we have amount random entry codes of length characters from an alphabet of size alphabet. The number of possible codes is then easily calculated as keyspace = alphabet ^ length. Now take an ...
6
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1answer
334 views

Who can certify RNG according NIST SP800-22?

I have written my own random number generator as a C library and I tested it on NIST Statistical Test Suite. Now I would like to get a certification to have a formal proof that my C library generates ...
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0answers
308 views

Using UUIDs for non-guessable URLs [duplicate]

How safe is using UUIDs as URL identifier for non-guessable IDs? Specifically UUIDs generated by Python's uuid4() function, using base64 encoding. E.g. https://example.com/content/...
1
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1answer
49 views

Can a salt maintain pseudo-randomness after being modified?

TL;DR: How much can a function (such as the one below) modify an initially random string before that string becomes useless as a salt for password hashing? Is there a general rule? # Function ...
2
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1answer
443 views

RDRAND in Intel Celeron CPUs under Linux

Is there any reason to believe that the hardware RNG in an Intel Celeron CPU is more unreliable than in other CPUs? Can someone confirm that what Linus Torvalds says is true, namely that Linux does ...
2
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1answer
281 views

Will two virtual machines running on the same physical host machine get the same value from /dev/random?

Will two virtual machines running on the same physical host machine get the same value from /dev/random if read over the same time period? Say that Virtual-machine-1 wants to generate its ssh host ...
2
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2answers
133 views

Which software RNG for linux?

A headless server can suffer from a lack of entropy, which is a problem given that encryption needs random numbers. In the absence of a hardware random number generator (RNG) the numbers must be ...
4
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1answer
595 views

Managing keys generated with insufficient entropy

Since the Linux RNG which provides /dev/random (and by extension /dev/urandom) is seeded by "mouse and keyboard activity, disk I/O operations, and specific interrupts" (source, PDF) and since virtual ...
2
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3answers
369 views

Offline RSA strong prime test similar to Phuctor?

One of the ways that RSA keys get consistently owned is when they're generated without enough entropy. Dan Kaminsky refers to a study which found that 1 in 200 RSA keys were badly generated and these ...
9
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1answer
5k views

What comprises the AIS-31 standard for TRNGs?

I'm researching how my smart card's chipset generates random numbers. According to a source in forums the YubiKey NEO is based on the A700x chipset from NXP. The page for the chipset indicates that ...
21
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1answer
3k views

Do randomized PIDs bring more security?

What is the concrete advantage of using random PIDs instead of traditional sequential ones? Some times ago, I've read an article in the french magazine MISC (no. 74 - July/August, 2014) publishing a ...
9
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2answers
2k 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), ...