A hash algorithm is a function which takes a variable size input and produces a fixed size output. The algorithm tries to make it difficult to predict the output for a given input, find two inputs with the same output, or reconstruct the input from the output.

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Differences between brute forcing access versus decrypting password files or databases

I was just reading about how it's better to use bcrypt to protect passwords instead of saving password hashes in databases, and that got me thinking about other aspects that hackers work on that I had ...
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Hash Function Xor

For a hash function what is the best secure method, XOR or Concatenate: h(data1 XOR data2 XOR data3 XOR data4) ? or use h(data1||data2||data3||data4)?
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662 views

Using passwords made of words

People say don't use passwords in the dictionary but if you use two words isn't it alright? Dictionaries have at least 10,000 entries so just two words will be 100,000,000 possibilities (and that's ...
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2answers
390 views

Is the password hash better when you concatenate the password and username?

Is the password hash (with bcrypt) better when You concatenate the username with password? For example: $this->hash($username . $password); and $this->hash($password); Last time I used ...
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2answers
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openssl: recover key and IV by passphrase

A large amount of files were encrypted by openssl enc -aes-256-cbc -pass pass:MYPASSWORD Openssl should derive key+IV from passphrase. I'd like to know key+IV equivalent of that MYPASSWORD. Is ...
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How to crack password hashed using SSHA?

Is it possible to crack a password hashed using SSHA if I know the salt? How can I do it?
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3answers
125 views

Clarification on an email about a security breach

I got the following email from a forum I was subscribed to: It is our duty to inform you that there has been a security breach on the server that Doom10 was being hosted on. It doesn't seem like ...
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2answers
468 views

Can a HSM be used to make password hashing stronger?

Say a database server has a HSM which is in use for encrypting (reversibly of course) credit card numbers. Is there any way a HSM could be used to add strength to a password hashing scheme? (Or are ...
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2answers
5k views

With PBKDF2, what is an optimal Hash size in bytes? What about the size of the salt?

When creating a hash with PBKDF2, it allows the developer to choose the size of the hash. Is longer always better? Also, what about the size of the random salt? Should that be the same size as the ...
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3answers
317 views

For what do I hash user passwords with PDKDF2 when the user data is stored in the same database?

I'm hashing the passwors of my users with PDKDF2 right now. A user can gain access to his account with his password. When the user is logged in he can edit his personal information and do other stuff ...
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2answers
384 views

In this example why do they hash a randomly generated piece of salt before hashing it with the password?

From here, in the code return substr(sha1(mt_rand()),0,22); what is the point of taking the sha1 value? It is appended to the password and together they are hashed using Blowfish. Why not just append ...
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Why is it necessary to match the checksum of a download with another file provided by the same server? [duplicate]

Possible Duplicate: Does hashing a file from an unsigned website give a false sense of security? On many servers providing files for download, there is a file on which checksums are ...
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4answers
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In hashing, does it matter how random a salt is?

I recently had a comment made to me in an online discussion after I'd stated that randomness in a salt doesn't matter -- and I got the following response: Salts may not have to be "secure," but ...
3
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2answers
355 views

What's the point of using multiple checksum algorithm with “aide”?

In aide the author offers more than one hash algorithm to do the check-sum, why is that? Aren't a single one, i.e sha512 enough for determining file changes? I believe these algorithms are all ...
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13answers
6k views

VP of IT claims he unhashed 100% of all 16k employees' PWs. Is he lying to us?

I work for a company which has ~16,000 employees. Periodically, our VP of IT sends out a newsletter with "tech-tips" and misc IT stuff. The topic of this week's newsletter was "password security". ...
19
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3answers
12k views

Is bcrypt better than scrypt [duplicate]

Possible Duplicate: Do any security experts recommend bcrypt for password storage? I'm no security expert and do not pretend to be that's why I'm asking here. I write many PHP based ...
14
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2answers
537 views

Password Salts and Randomness

Alright, so I understand that users are the kind of beasts who like to use one password and make it short and easy to remember (like "doggies"). If I understand correctly, that's one reason we use ...
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5answers
374 views

Is there value in storing passwords in their own table with encrypted or hashed keys?

The usual method for simple sites is to store a hash of a user's password right in their user record. What if the password field is removed from the user table, and a password table is created? The ...
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687 views

How to evaluate the strength of a hashing algorithm?

At work the hashing algorithm we use for passwords appears to be bespoke. Obviously that's a pretty bad idea, but the management don't seem bothered. The algorithm always produces 20 character long ...
10
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2answers
37k views

OpenSSH default/preferred ciphers, hash, etc for SSH2

When using OpenSSH server (sshd) and client (ssh), what are all of the default / program preferred ciphers, hash, etc. (security related) and their default options (such as key length)? So, what are ...
4
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1answer
340 views

How big is the risk of hash fixed points/cycles?

It's established wisdom to hash password multiple times with a salt to increase the time it takes per brute force iteration. At the same time (unless the algorithm guarantees otherwise) there's a ...
3
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2answers
254 views

Doesn't adding requirements to a password, such as must contain 2 digits, decrease the strength? [duplicate]

Possible Duplicate: Doesn’t imposing a minimum password length make the password weaker by reducing the number of possible combinations? Doesn't any constraints added to a password policy ...
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7answers
783 views

To salt, or not to salt? [duplicate]

Possible Duplicate: Why is using salt more secure? Why would salt not have prevented LinkedIn passwords from getting cracked? Recently I decided that I wanted to learn more about web ...
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2answers
1k views

Do OpenPGP/GnuPG apply slow hash to password when encrypting/decrypting key?

Password space is quiet small. Therefore slow hash should be applied to password before using it for encryption. Should slow hash function (like bcrypt) be applied to password before using it with ...
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1answer
269 views

Password protection of encryption and signature keys

I would like to store encrypted backup of text files on my computer. I'm developing a python script using Pycrypto to achieve that, based on this code to use the library. (current code) The basic ...
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what is the fastest and cheapest way to crack this kind of hash - md5(md5($password) + salt))?

I'm looking for a program that can use any GPU (ATI\NVIDIA) and can brute force a vBulletin hash - md5(md5($password) + salt)). I have the salt and hash. the password contains the symbols - ...
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3answers
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Is my session-less authentication system secure?

So, I've created an authentication system. Poured over it for any kind of security flaws and tested the crap out of it. I think it's fairly secure, but there is one "different" by-design aspect of it ...
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5answers
569 views

Does shuffling a hashed password increase its security?

I am making a web app and I'm now stuck on making the login secure. I'm thinking of adding a salt to a user-inputted password and then hash it. (md5 or sha for example) and then I will reshuffle the ...
2
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1answer
2k views

Clarification on how rainbow tables work

If you goto : http://www.hanewin.net/encrypt/aes/aes-test.htm for "Key in Hex" enter 00000000000000000000000000000056 for "Plaintext in Hex" enter 00000000000000000000000000000000 and click on ...
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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. ...
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6answers
2k views

Is there a table that compares hashing algorithms by speed, relatively (machine independent)

As far as I understood*, one of the major criteria when choosing a password / salt hashing algorithm is it's speed. To prevent brute force attacks, a slower algorithm is better (and also makes it more ...
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1answer
110 views

How are root CAs for SSL distributed?

For internet explorer or whatever, I get it... It's in essence a sneakernet, you get them on the physical media from which you install your system and browser. But what about for firefox and chrome? ...
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Key stretching an hash

if I implement an function which hashes the first half of my password with MD5 and the second half with SHA2 and MD5. Is there a security issue when I put these two hashes together to a 64 character ...
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1answer
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Replacing weak SSH fingerprint algorithms

Even though MD5 has been broken for years and its vulnerabilities have been used to create real-world rogue X.509 CAs and other horrible things, OpenSSH and PuTTY still use MD5 as the default public ...
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Is AES slower to encrypt than MD5?

Is this the right interperation of this diagram: http://www.cryptopp.com/benchmarks.html AES/CCM MiB/Second:61 Cycles Per Byte:28.6 MD5 MiB/Second:255 Cycles Per Byte:6.8 And does that ...
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0answers
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Finding pre-image of MD5 hash [closed]

I have the following requirement for hashing using MD5. H(A,B,C,X); Where values A,B & C are given. However X is not given. I would like to find out what value of X would give a hash beginning ...
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1answer
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Is there a better way to take advantage of current 'approved', 'proven', and memory/cpu-expensive algorithms while using salts and peppers?

I've read about the concepts presented in these two questions: Pre-hash password before applying bcrypt to avoid restricting password length Would it make sense to use Bcrypt and PBKDF2 together? I ...
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2answers
1k views

Program binaries or files with same MD5 hash

I'm looking for 2 different program binaries or 2 different files with the same MD5 hash to prove its weakness and the collisions in the algorithm.
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2answers
3k views

Estimating the size of a rainbow table

What are rainbow tables and how are they used? Gives a very precise answer about what rainbow tables are and how they are used. I had always confused hash-tables and rainbow tables. My question is ...
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3answers
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Does the salt need to be unique or not predictable?

I always thought that salts is simply used to prevent rainbow tables to be used. Other have suggest they should be unique on a per account basis. Currently i have been using a config file to use as ...
20
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5answers
4k views

What's the practical limit for rainbow-table based bruteforce?

Say we have a hash of a password. The password can be considered to be made of of totally random characters and has a fixed length of N. The hash is SHA1(password+salt), where the salt is of length M. ...
14
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6answers
839 views

Is there any security risk in storing hashed variations of passwords?

For example, if hypothetically an application requirement was to tell users when their password might have failed because caps-lock was turned on, and hypothetically there was no way for the ...
20
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4answers
2k views

What to transfer? Password or its hash?

Let's say in my database I store passwords hashed with salt with a fairly expensive hash (scrypt, 1000 rounds of SHA2, whatever). Upon login, what should I transfer over the network and why? Password ...
26
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4answers
10k views

https security - should password be hashed server-side or client-side?

I am building a web application which requires users to login. All communication goes through https. I am using bcrypt to hash passwords. I am facing a dilemma - I used to think it is safer to make a ...
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2answers
694 views

Password entropy match for alphanumeric but there are special characters in password

I have a problem cracking some of the fundamentals on passwords' entropies. Namely: I have read this article about a guy cracking DKIM of Google (maybe more noticing that the keys are only 512 bits) ...
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2answers
2k views

Is it okay to widely share the RSA key fingerprint for a host?

When you ssh into a remote box for the first time or if the remote host's key fingerprint has changed (from what's stored in your known_hosts file) you get a warning and you are shown the fingerprint ...
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MD5 collision attacks: are they relevant in password hashing?

DISCLAIMER: This is not an endorsement of MD5 as a password hashing function. I know about parallelization, GPUs, and dedicated password hashing functions like bcrypt and scrypt. With that out of ...
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Password Security: Encrypting salt [duplicate]

Possible Duplicate: Password Hashing add salt + pepper or is salt enough? I'm new to security and trying to understand why encrypting or hiding a salt is not considered useful. I've read ...
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3answers
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rsa encrypted hash == rsa signature

$ echo -n "1327943823" > test_ok.txt $ openssl dgst -sha1 -binary -out test_ok.sha1 test_ok.txt $ echo "GURbsl4CFPCG83RCZxsEpoRleXicXQhH1OC4Fk77b7EMj2g8aHUhD/L+sm ...
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3answers
446 views

Hashed passwords - How many variations of rainbow tables?

First off...I passed the CISSP exam. WOOOO. I had to get that out. GCIH and CEH by Sept. 11' So, while studying for the technical side of things, I see that there are rainbow tables. They are ...