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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mathematically / theoretically, what is the chance that 2 different inputs would have the same results of 2 different hash functions?

mathematically / theoretically, what is the chance that 2 different inputs would have the same results of 2 different hash functions? As an example, i will use 2 weaker hash algorithms, the MD5 ...
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Trying to understand password hashing

I am trying to get a grasp of password hashing. Back in the days it seemed so simple, just MD5(password + salt) and you are done. Then md5 was proven to have collisions so people started moving to ...
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SHA, RSA and the relation between them

SHA is the hashing mechanism. However, RSA is the encryption algorithm. So does RSA algorithm use SHA hashing mechanism to generate hashing keys which in turn is used to encrypt the message?? ...
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How to upgrade the hashing method of a live database without compromising security?

I'm working on an Intranet project that is accessible from the outside. The password are stored in a Sql Server database in the normal Hash and salt method. The problem lies in the hashing algorithm. ...
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What algorithms are best be cracked by GPU?

What algorithms are best being attacked by a GPU powered password cracker? For example, I heard that md5crypt that is being used in unix shadow file, is not the best choice for GPU cracking because it ...
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Bank account number and account holder in check exposed?

I'm not sure if this is standard practice in all banking institutions but almost all banks where I've received checks the account number of the issuer is exposed (some even the account name). Isn't ...
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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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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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548 views

Does checking the fingerprint of a self signed certificate improve security?

I am currently developing a component for an application that does TCP communication with a device inside a local area network. I use TLS to provide data encryption, integration and authorisation. ...
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411 views

Use of rainbow tables with the NY Times hack?

The NY Times recently published a story about how they were hacked during a four month period. The hacks allegedly were carried out by part of the Chinese military. One part of the story that ...
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bcrypt: random salt vs computed salt

I'm pretty new to the whole password hashing business, so I might be missing something obvious. I was looking at the bcrypt algorithm, in particular BCrypt.Net, and I was wondering if it wouldn't be ...
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Do SSD's offer significant performance boost for Scrypt?

Being a memory intensive hash, I was wondering if SSD's offer any appreciable performance boost for brute force attacks.
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566 views

Zero padding in HMAC

Section 2 of RFC 2104 defines the key used in HMAC should be padded with zero bytes up to the block length of the underlying hash algorithm. Isn't this a potential security vulnerability since any key ...
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Should we start using SHA-3? [duplicate]

Possible Duplicate: What is SHA-3 and why did we change it? SHA-3 has been finalized! So, what does secuirty.se think about the new hash funciton? Should we start replacing all uses of ...
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398 views

Why is 8ms a goal for hashing?

I'm currently developing a small project in PHP, and as it involves user authentication, I've been researching what options I've got regarding hashing. I've settled on PBKDF2 primarily due to it's ...
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Is the execution time for bcrypt independent of the length of the input string?

Is the execution time for bcrypt independent of the length of the input string? i.e. Should the execution time of bcrypt.hashpw('input_string', bcrypt.gensalt(12)) and ...
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Is it a good idea to have a “master” password?

Though I do have a good memory of passwords, it is quite impossible to have one password per application. Yet, it should be... My current way to deal with passwords is to have five passwords and to ...
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324 views

Is cascading cryptographic algorithm better than using a single one?

Am I wrong to think that scrypt(bcrypt(password)) would be better than using sole (s|b)crypt? Especially when considering two different key for the two algorithms. I am also interested in some ...
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Complexity of web certificate attacks

I heard a while ago about someone exploiting md5 weaknesses to create a web certificate with the same md5 that a different certificate has. They were able to create a certificate through bad issuing ...
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317 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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Reference implementation of C# password hashing and verification

Does anyone have a reference implementation (ideally 3rd party certified, or government approved) way one-way hash a password for C# and or Java? Ideally,I'd like to see something that includes a ...
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609 views

Secure authentication: partial client-side key stretching… please review/criticize my idea

I am trying to figure out what would be the 'perfect' authentication system for a website. On one end, we know that simple hashing algorithms can be brute-forced or cracked in other ways. Hence why ...
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Revisting the Username Hash

There are a few questions which ask for inputs on the wisdom of storing (possibly salted) username hashes for the purpose of authenticating end user access to some information resource. Most of the ...
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How valid is the concern over narrow pipe hash function designs?

Narrow pipe hash function designs have recently come under fire, particularly in reference to some SHA-3 candidates. Is this criticism valid? Can it be explained more simply than this paper does? I'm ...
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What is the meaning of the term “simple string” for the SALT string in Unix crypt using SHA-256 and SHA-512?

In Unix crypt using SHA-256 and SHA-512 the author, Ulrich Drepper, introduces the SALT string as the following (highlight by me): For the SHA-based methods the SALT string can be a simple string ...
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How should I choose a difficulty factor for my password hashing function?

Assuming that I'm doing password hashing properly and using bcrypt, scrypt or PBKDF2, how should I go about choosing an appropriate difficulty factor? i.e rounds for bcrypt, iterations for PBKDF2 and ...
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Keeping user data private in a cloud environment like Google App Engine

I am writing an open-source Java application for Google App Engine (GAE). The application will let users create content that is intended to be private. I want to provide reasonable assurances that ...
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Definitely safest password storage scheme?

I already asked this on StackOverflow but I was suggested this would be a better suited place and I found no way to "move" the question so I have to copy it. Believe, I know, there are hundreds ...
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Use the hash of the password to encrypted password

I have a app which transmit the password in clear text. I was planning to use the hash of the password (SHA-512) as the key for encrypting the plain text password. Then send the encrypted text to the ...
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Brute force vs other methods of recovering passwords from shadow file

Do you know any good approach for de-hashing/actually bruteforcing hashed passwords in the shadow file? On various operating systems, any good solutions/methods/programs. Or is it better to upload ...
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Does Hash/Salted password really help when DB is compromised?

I came across this article and got a basic understanding hash, salt and brute force attack. My question is in the article, the author emphasises how hard it is to reverse the hash/salted password to ...
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What is better salted hash or openssl encryption?

Im using php and I was looking to store passwords in a mysql database. I was wondering what would be safer to use a salted hash or openssl encryption? If i use a unique random generated salted hash ...
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What is the purpose of a Pepper?

I've been trying to find out exactly what a pepper is. The only things I could accurately determine are that a Pepper: Is theoretically unique from site to site and hard-coded in the site's source ...
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Windows 7 Password Hash Security

I recently came across a number of sources that suggest that cracking Windows user account passwords is easy by examining their password hashes. I understand that these hashes are stored in the SAM ...
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Can DES-based hashed password be recovered if salt is known?

Can a hashed password be recovered if the hashing is done with DES based crypt function in PHP and both the hash and salt are known by the attacker? Consider the following example: $salt = 'mysalt'; ...
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usernames and passwords

I was thinking about usernames and passwords and I was wondering how secure it would be to instead of the server having a list of usernames and accompanying hash of the passwords, just have a list of ...
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Rounds of MD5 and SHA512 Hashing Algorithms

What is the exact number of rounds employed by the MD5 and SHA512 hashing algorithms? According to various sources, the SHA512 hashing algorithm employs a total of 80 rounds ...
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Salting a public hash

Does it make any sense at all to salt a hash which might be available publicly? It doesn't really make sense to me, but does anyone actually do that? UPDATE - Some more info: An acquaintance of ...
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What security purpose do hashes of files serve?

Many websites offering downloads also provide the MD5 or SHA1 hashes of the files which are available for download. An example- What is the security purpose behind providing such a facility to the ...
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How does processor architecture affect password hashing speed?

Does hashing speed vary significantly using different architectures (x86 vs ARM)? Scenario I am investigating the possibility of using a cluster of Raspberry Pi for cracking passwords hashed with ...
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Tracking unique web site visits without logging IP addresses

On Monday, some IP address xxx.xxx.xxx.xxx visits my site. I log it. On Tuesday, another IP address yyy.yyy.yyy.yyy visits my site. I log it. If the two IP addresses are equal, I throw out the ...
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symetric key encryption vs hashing

This is a fascinating document: top 100 passwords from adobe breach I have a question about one part of it: However, thanks to Adobe choosing symmetric key encryption over hashing, selecting ...
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Is it good practice to SHA512 passwords prior to passing them to bcrypt?

I want to allow any-sized passwords to be allowed to be submitted. I currently use bcrypt as a key derivation function for passwords, however I have realized that it has a maximum input length of 72. ...
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578 views

When hashing passwords, is it okay to store the algorithm used right there in the database?

Since hashing password has become a hot topic recently, it is only natural to expect things to change and assume that some time down the road you might want to replace/tweak the algorithm used in your ...
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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 ...
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What is the purpose of using Youtube-style alphanumeric ids as URL slugs?

I asked a question on StackOverflow on how to generate the alphanumeric/base64 resource IDs that Youtube, Instragram, and others use to identify videos/pictures/etc. Discussion led to the question of ...
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124 views

OS Kernel Hashing

Has anyone had experience with or is aware of any products that hash the OS kernel? This would be used, ideally, for watching for system compromises, auditing, change management, etc. I am looking ...
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503 views

Is it safe to use PBKDF2 for hashing?

I would like to get a few opinions on whether it would be safe or not to use PBKDF2 to generate a hash of a password. For my purposes I'd like to assume that the hash itself will be posted on the ...
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User password as key instead of hashing it

I was reading here on Hashes and Salts and I thought about another method to do user authentication. I need your thoughts on this as I might be overlooking something. Scenario: For web application ...
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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 ...