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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Is there a hash algorithm that can identify similar files or strings?

Is there a hash algorithm that will help you identify similar files or strings? For example, the hash for ABC and XBC would be similar rather than radically different as is usually the case. I know of ...
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comparing password hashing algorithms - PoC ideas?

OK so I just started working for a security consulting firm and we recommend SHA 256 (with salt) for password hashing because MD5 is too weak. I have read some brilliant answers (the list is too ...
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Could a password hash that's prone to more collisions provide better overall security?

Website security breaches seem to be a common occurrence, giving the attacker password hashes that he can conduct a brute force attack against, often given him a list of passwords that will work on ...
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Expanding/Inverse Hash function

First off, before I ask my question, let me explain what I am NOT asking. I am NOT asking for a way/method to reverse a hash output; by definition, a hashing function is one-way. Is there such a ...
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Hashing a key: less entropy than the key itself

A web API needs to store a 'key' for authentication, in much the same fashion as a password but at 128 characters. My concern is that the salted SHA1 hash for the key has less entropy than the key ...
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What steps can you take to make offline cracking of SRP harder?

In the aftermath of the Blizzard hack, what steps can I take to make offline cracking of SRP more difficult? My question assumes that your database is already gone and that you implemented SRP more ...
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Can hash functions be used with CTR or OFB mode?

I have been writing a class that encrypts and decrypts with block ciphers. I want to use Counter Mode(CTR/CM). We know that Counter Mode generates a keystream basing on counters, then XOR the ...
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Is encrypting a salt value with a password/plaintext a viable alternative to straight up hashing?

The basic problem, as far as I can tell, is that hashing's flaw is that the password is in the hash. Asymmetric encryption's flaw is that the password is encrypted and can be reversed. The posts ...
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openssl_digest vs hash vs hash_hmac? Difference between SALT & HMAC?

openssl_digest vs hash vs hash_hmac I want to use SHA512 for storing password. Which of the above methods are best to use? Why? What is the difference between SALT & HMAC? I just read ...
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Truncating the output of SHA256 to 128 bits

suppose we need/prefer 128 bit hash output. for example to generate a 128 bit encryption key or, in other applications (e.g. file integrity verifications), to consume less storage space. i don't know ...
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625 views

Reducing password length with hash function

Suppose I would like to use a very long string as a password. As an example we can just say this string is 100 characters in length. However, suppose the application for which I would like to use ...
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What about combining pkdf2 with scrypt? [duplicate]

Possible Duplicate: Would it make sense to use Bcrypt and PBKDF2 together? How does the following password hashing scheme look to you? iterations1 = scrypt iterations required to spend ...
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790 views

Bcrypt as a key derivation function?

I read a lot of entries at stack exchange about bcrypt and why it is supposed to be better than PBKDF2 in terms of password storage. I'm asking now if bcrypt is better than PBKDF2 in terms of key ...
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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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Is BCrypt enough when saving a password into a database?

In order to allow users to connect to my website, I encrypt their password using BCrypt since it is one of the slowest algorithms to decrypt (making a compromised database longer to be decrypted). ...
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PHP Vulnerability May Halt Millions of Servers - max_input_vars!

Recent version of PHP 5.3.9 has been released a couple days ago, and Hash Collisions have been fixed, most of the servers actually didn't upgrade their server until now, including my website's server. ...
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Standards for CA cert revocation and time-constrained cryptographic algorithm parameters

I'm working on software that will be in use for foreseeable future (15 years+) that will need to validate XAdES-A signatures (long term archival, similar to PAdES-A, but for XML). That means, it will ...
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Why is password strength often underestimated and uncertain in the context of password hashing?

An aspect of security has bugged me for a long time: Why is there positive certainty about the importance of hashing algorithms and salts, but password strength is either never mentioned at all or ...
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Is every hash format that nginx accepts for HTTP Basic Auth weak against brute force?

According to http://nginx.org/en/docs/http/ngx_http_auth_basic_module.html nginx can read password hashes of these types: crypt(), apr1, SHA1 & SSHA. This is how I understand how these hashes ...
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Is PBKDF2 only SHA1 in C#?

I can't find a way of specifying the hashing algorithm used by the PBKDF2 (the Rfc2898DeriveBytes class) implementation in C# System.Security.Cryptography. It seems to be just SHA1. Am I missing ...
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Rainbow tables, generation and lookup, preferably using GPU

1a) What software can I use to generate my own rainbow tables, preferably software that can utilize CUDA or ATI Stream? One of the reasons I want to make my own, is that I want to use a specific ...
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Will my method for managing account data work?

I'm looking at whats nessecary to create a small accounts server for a video game I'm programming in my spare time. User privacy is a very important topic for me, and I don't want to keep anything ...
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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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How to tell if a site is securely storing passwords? [closed]

A site I frequent has a policy to make you change your password every 90 days. That's a cool policy, but I stumbled upon an old xkcd and facepalmed myself, because lots of doxing happens on this site. ...
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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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Is this a secure way of storing passwords? [duplicate]

So a couple years ago when I was learning basic back-end web development, I found a tutorial for creating a basic log in system. I haven't done much modification to the code since, but I have the ...
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Irreversible hashing without collision

We are looking to allow users to log on with a smart card. The smart card reader can read the smart card ID and send it to us. We are, however, not allowed to store the smart card ID. Not in ...
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504 views

Is this security/encryption scheme secure?

I'm rolling my own, personal threetags.com-style 'encrypted data in the cloud' webapp (I didn't like the UI, and lack of non-browser client). However, I have absolutely no experience with security ...
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SHA and “Bits of Security”

I've researched several forms of encryption/hashing and have often come across the term "bits of security". For example, at least one source claimed SHA-256 = AES128 = ECC256 = 128 bits of security. ...
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Why do most hashing functions produce hashes that have characters a-f 0-9?

This is something I never understood about hashing functions. I know that algorithms like whirlpool and blowfish both produce outputs that don't follow this pattern, but why is it that most do? Is ...
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Are there any websites that gather hash sums of different disk image files?

For example the SHA256sum of an Ubuntu ISO image, or an OpenBSD amd64 image. Are there any sites? It's important that the site must use HTTPS or at least it must provide GPG check for the hashes.
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True?: “Nearly all encrypted passwords are stored with the last character in clear text”?

[S]ome passwords are gleaned by hacking into computers where intruders can find stored passwords. Those are stored in encrypted form, but there's software that can attack the encryption. Nearly ...
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Are hash functions “strongest link”?

It seems to me that if you were to use multiple hash functions, the "strongest link" would hold up the others. For example: HelloWorld --- md5 --> 68e109f0f40ca72a15e05cc22786f8e6 --- sha256 ...
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Salted hashes vs HMAC?

Most of discussions involving access credentials include references to "hashing salted passwords". Is this another way to referring to the HMAC algorithm or a totally different operation? Different or ...
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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 to properly anonymize data, if hashing isn't enough?

Today there are news on Bruce Schneier's blog and ArsTechnica about how NY City released information about Cab/Taxi drivers, their trips, and so on. Basically, sensitive information was simply MD5 ...
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Is it a good idea to store Email addresses as hash only?

I am currently building a web service at http://write-math.com similar to http://detexify.kirelabs.org/ that should help users to get LaTeX code from drawn formulae. It is part of my bachelors thesis ...
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Why not hashing and salting passwords?

When I was implementing my webapp, I decided to hash and salt users' passwords in order to protect them, even though I knew that there will never be a lot of them ... if any. Of course, I'm not saying ...
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Is there any way to cryptographically hash a human thumbprint?

Is there any way to cryptographically hash a human thumbprint into a form that can be consistently reproduced by thumbprint readers? Assuming that it would be possible to create a database of ...
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Is mt_rand() suitable for generating a salt?

Assumed I have to following code in order to generate a random blowfish salt for saving a new password: $blowfishCharacters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789./'; $salt ...
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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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Can the salt for PBKDF2 be a hash of the user-entered password?

I want to derive a key from a password in a client application that will be used as a master key that decrypts a data key. As far as I understand the salt should be private knowledge. Would it be ...
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MD5 display format

When I run MD5 algorithm I am getting an output in numeric and a few lower case letters. Obviously it uses all numeric digits and rarely i saw some lower case alphabet letter. I need to understand ...
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Why doesn't Microsoft implement salt on users passwords in Windows?

Pretty straightforward - So we use rainbow tables to get passwords of users out of hashes. So why won't Microsoft implement salt on the passwords in Windows to be hash(password+salt)? Won't this ...
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Why does MD5 hash starts from $1$ and SHA-512 from $6$? Isn't it weakness in itself? [duplicate]

I have moved this question from stackoverflow to this place. I know it may be a question about 'opinion' but I am not looking for a private opinion but a source of the final decision to keep it this ...
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How can I store a password history to prevent reuse?

I have an application with a user database. The database stores the password using a bcrypt hash with a randomized salt. How can I implement a password history set (to prevent password reuse) in a ...
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When salting and hashing passwords, any advantage to including password length?

In this answer, Gilles says (emphasis mine): There's no need to hide the salt from the attacker: it needs to be unique (and not derived from the password) but it doesn't need to be more secret ...
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The security level in hash function

What is the difference in security between using part of message digest hash function or all the message digest hash function? and is there any equation can calculate the security for part or whole ...
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Is it safe or even common to cache bcrypt checks in-memory

In a web application that (as a side effect of implementing the password anti-pattern) stores passwords, one recommendation is to bcrypt to store them (or computationally expensive one-way salted ...
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Record IP pseudonymously?

I'd like to be able to ban an IP from my website, but for privacy reasons I would like to not have a record of the IP itself. Hashing the IP would allow for the hash to be brute forced in mere ...