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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What's the use of making users use digits, uppercase-lowercase combination password if the passwords are hashed?

Some websites, even the StackOverflow asks for atleast 1 digit, 1 uppercase character in the password. Does this really matter when the developer uses a password-hash algorithm to store the passwords ...
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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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How can I extract the MD5 hash of a password protected MS Office Word 2000 document?

AFAIK, the compound file format identifier is D0 CF 11 E0 A1 B1 1A E1, which is located in the offset 0 of the header, which has a length of exactly 512 bytes. However that is not enough to get the ...
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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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Is it possible to detect password length from hash? Does doubling your password add more security?

Assuming a service doesn't store a plain text password, am I right in saying that the answer to this question depends on the service? On a bad service, the hash length is related to the password ...
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Will SHA1 of Email Addresses Always be Unique?

We want to store data about a person without storing their email address, but we want to latter connect that person with their data upon them supplying their email address. Storing a SHA1 of their ...
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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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Tool for generating MD4 collisions

There are a lot of research papers available online that discuss vulnerabilities of MD4 algorithm, but I couldn't find any implementation of these. Uptill now I have used tools like John the Ripper ...
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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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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 ...
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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. Which function is better to use to generate a random salt for password security? $salt = sha1(openssl_random_pseudo_bytes(23)); or $seed = ''; $a = ...
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Proving running code on a website is unchanged

Can it be proved to the user that the running code behind a website with security related code is the same as published? I'm currently looking at a few new project ideas and one involves secure ...
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1answer
341 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 ...
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4answers
688 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 ...
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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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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 ...
295
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10answers
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Is my developer's home-brew password security right or wrong, and why?

A developer, let's call him 'Dave', insists on using home-brew scripts for password security. See Dave's proposal below. His team spent months adopting an industry standard protocol using Bcrypt. ...
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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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5answers
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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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Why don't people hash and salt usernames before storing them

Everyone knows that if they have a system that requires a password to log in, they should be storing a hashed & salted copy of the required password, rather than the password in plaintext. What I ...
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Gold Standard for password hashing

I've developing a web application that will be dealing with highly sensitive information and I want to ensure the hashing of passwords is gold standard. Ideally I'd go for per-user salted SHA512 ...
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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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Are SIP REGISTER transactions w/ HTTP Digest subject to replay attacks?

It is my understanding that the authentication during a SIP registration is done through some kind of an MD5 hashing algorithm known as HTTP Digest, and doing a tcpdump of the actual traffic I've ...
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4answers
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Antivirus Engine based MD5 or SHA1 hash?

I'm trying to understand more about MD5 and SHA1 hashes algorithms and their behavior in serious security software(found this but not helped me more). Why does ClamAV use additional scanning ...
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Choosing a session ID algorithm for a client-server relationship

I am developing an application which has a client-server relationship, and I am having trouble deciding on the algorithm by which the session identifier is determined. My goal is to restrict ...
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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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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 ...
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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". ...
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1answer
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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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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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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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Validate hmac with hashed stored key

What if an HMAC is correctly generated and sent with the data to the server, so far I know the server needs to know the original data with which the MAC was created in order to re-create the MAC and ...
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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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Is a simple, but very long password a good password?

Is a password like wwwwwwwwwwwwwwwwwwwwwwwww9 (25x 'w' and a number) secure? It would be easy to remember.
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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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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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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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1answer
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Parsing a PKCS7 detached signature hash

I'm trying to manually verify signatures of Apple iOS Passbook files, which are PKCS #7 detached signatures of the RSA key of the Apple developer who created the file. Which means there's a file ...
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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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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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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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Client side password hashing

Edit: Updated to put more emphasis on the goal - peace of mind for the user, and not beefing up the security. After reading through a few discussions here about client side hashing of passwords, I'm ...
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1answer
241 views

Seeding GPG keygen with a hashed secret [duplicate]

Possible Duplicate: Tool for public key cryptography where password is the private key? I was wondering if you guys could clue me in to potential problems with using a hashed password as ...
2
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1answer
972 views

Password authentication using DynamoDB

I'm working on a Mac app. I have users stored using DynamoDB. Authentication is needed to enforce access control on system-internal operations, such as uploading files to Amazon S3. Of course, I ...
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1answer
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Security of re-encryption with a list of pre-computed password based keys

I have a problem where an encrypted file stored on a server needs to be decrypted through a precomputed list of passwords that are used one time only - OTP applied to encryption basically. The file is ...
18
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Doing a dictionary attack on RSA if you have the public key?

I'm trying to learn exactly how RSA works. Currently I have a very, very simplictic overview that goes like this. Having the public key allows you to encrypt things. Encrypting the same message ...
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How to know if its the same User?

I asked a question awhile ago asking how to make an efficient encrypted chatroom. What I ended up doing was Making each user generate a 4096 bit RSA KeyPair, share their public Keys, and then one of ...