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

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1answer
211 views

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 ...
0
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1answer
59 views

ssh-keygen: How is the seed generated?

How is the seed for ssh-keygen generated? I expect it will take information from /dev/random and request supplementation with system activity if we have insufficient random bits. An Instructor ...
18
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6answers
3k views

What does “random” mean in the context of password creation?

Disclaimer: as you will see from my question I'm a total outsider in this subject, just very curious. I was wondering how easy it would be to crack a password-protected RAR5 file, and I found many ...
4
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1answer
87 views

Ways to generate symmetric and asymmetric keys

We are using Beaglebone Black based custom board, and want to use hybrid encryption for encrypting firmware file, i.e. symmetric for encryption big firmware file and asymmetric for encrypting ...
9
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2answers
1k 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 ...
3
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2answers
127 views

Are password generators secure?

Here's a scenario that I often encounter: Some user needs access to something on my network, but they don't have an existing account in AD. I create an AD account for them which I then use to allow ...
0
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0answers
43 views

Choosing Key and IV in AES-256

I am working on a real-life project for a firm. I have to encrypt data using AES 256 as per specification. I want to know how are the key and IV are really chosen in real world projects. /dev/urandom ...
4
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1answer
267 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 <...
9
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1answer
521 views

Do randomized PID 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 ...
12
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3answers
3k views

Is a concatenation of random numbers better than a single random number?

We are generating random numbers 16 digits in length. One option that was put forward was to generate four random numbers of 4 digits each and concatenate them instead of just generating a single 16 ...
1
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2answers
1k 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(...
14
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4answers
2k views

Predicting Math.random() numbers?

I was reading up on the documentation for Math.random() and I found the note: Math.random() does not provide cryptographically secure random numbers. Do not use them for anything related to ...
27
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11answers
6k 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 ...
1
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3answers
315 views

How to generate random but unique tokens for authentication?

I need to create unique and long tokens for email verification, but I am not sure about how. Currently we are on staging servers or we are just using os.urandom() in Django. But I need to know what ...
5
votes
1answer
107 views

How bad it is to feed /dev/random with /dev/urandom?

I have seen many blog posts, or blog comments which recommends to feed /dev/random entropy using output from /dev/urandom. I'm not a crypto expert, but it looks like a good way to replace hard-to-...
0
votes
1answer
88 views

Is `/dev/urandom` secure to generate a salt on a Virtual Machine?

I've read the new password_hash() function from PHP uses /dev/urandom to generate a secure salt, however this assumes some noise from device drivers. Is possible that /dev/urandom is not so random ...
7
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6answers
143 views

Should I use a cryptograpically secure random number generator when I generate IDs?

It is common to generate random identifiers to expose through an API instead of using a simple auto incrementing primary key. The reasons are many: Prevents easy enumeration. Does not give away ...
5
votes
2answers
206 views

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 ...
1
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1answer
26 views

Synchronized nonce

If two parties (Say A and B) have a shared secret key (K), is there any way for each party to use the shared secret key to generate nonce(N) sequence which is equal on both sides without having to ...
3
votes
1answer
69 views

Is this good/secure method for client-server communication encryption?

Something came to my mind, and I wonder if this is proper method for client-server communication, and if this method is wide-used. On connection, client generates seed, encrypts it using asymmetric ...
3
votes
1answer
56 views

Should I use random usernames for a MySQL database? [duplicate]

I have a script that accesses a MySQL database - clearly a strong, random password and a username unique to the script with no more privileges than it needs are all sensible norms here. However, is ...
5
votes
1answer
117 views

Simple, Secure PHP API Design

I'm trying to design a secure RESTful API web service with as few moving parts as possible. I have some questions, and want to make sure my design is secure. For the data transmission level of ...
2
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2answers
113 views

Are there any security advantages to the “TrueCrypt-Paradigm”?

TrueCrypt and its successors use a file format that has the special property, that it looks completely random, there's only a salt (which is random) and the cipher text (which looks random). I like to ...
3
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2answers
109 views

How significant are these Dieharder results on a Raspberry pi

I was running the Dieharder test suite on my raspberry pis hardware random number generator, and it came back with this: root@raspberrypi:/home/pi# dieharder -a -g 201 -f /dev/hwrng #=========...
3
votes
1answer
69 views

Is SHA1 / PBKDF2-HMAC-SHA1 indissociable from random data?

I want to make sure that the result of PBKDF2-HMAC-SHA1 is indissociable from random data (given random parameters). Basically, PBKDF2-HMAC-SHA1 looks like just a bigger SHA-1 hash, which is normal ...
3
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2answers
90 views

Is it possible to crack g++ rand()?

So, I have this: I know that some code was used to generate a random sequence, and it looked roughly like this: #include <iostream> #include <string> int main() { const std::string ...
11
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1answer
203 views

How long to re-seed /dev/urandom in a virtual machine?

I have read plenty about the distinction between /dev/random and /dev/urandom. I understand that the prevailing advice is to use /dev/urandom. The explanation - that 256 bits of 'proper' randomness ...
18
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3answers
2k views

Flaw in encryption through pseudorandom number stream (from PGP 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 ...
1
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1answer
46 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 ...
4
votes
1answer
52 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 ...
1
vote
1answer
63 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, ...
3
votes
1answer
104 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 ...
0
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1answer
29 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
70 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 ...
47
votes
6answers
8k views

Are random URLs a safe way to protect profile photos?

I would like to move from sequential to random user IDs, so I can host profile photos publicly, i.e. example.com/profilepics/asdf-1234-zxcv-7890.jpg. How long must user IDs be to keep anyone from ...
17
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5answers
5k 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, ...
0
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3answers
117 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
votes
1answer
70 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
votes
2answers
69 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 ...
1
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1answer
98 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? ...
5
votes
1answer
124 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 ...
38
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9answers
27k views

Feeding /dev/random entropy pool?

Which way of additionally feeding /dev/random entropy pool would you suggest for producing random passwords? Or, is there maybe a better way to locally create fully random passwords?
3
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1answer
101 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 ...
5
votes
1answer
307 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 ...
14
votes
3answers
16k 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 ...
1
vote
1answer
4k views

Generating a TRULY random string in PHP [duplicate]

I need to generate thousands (possibly millions) of unique codes for a client. These codes may have a monetary value, so it's vital that they are TRULY random, and that no pattern could be spotted and ...
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0answers
62 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 ...
5
votes
1answer
116 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 ...
2
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2answers
54 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 ...
3
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0answers
82 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 ...