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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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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3answers
712 views

Global check of input/output of known hash functions

Is there a website, application, or script that will allow you to give an input/output for a hash function, run these against known functions, and return any matches? Here's one attempt to list the ...
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2answers
702 views

Are different hash algorithms ever used together?

I was wondering if different hashes (e.g. md5(sha1($data)) ) are ever used together for data security and if there was any reason for it (either positive or negative answer).
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9answers
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What is the best way of securing a website logon without SSL or preshared keys?

Today I sniffed some unencrypted wlan traffic during class and I found quite a few passwords by a simple search for "pass" and "user" in wireshark. Turns out about half the sites we use for school ...
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6answers
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Convenient cross-platform help on checking secure hashes like SHA-256

It is often helpful to be able to obtain a good cryptographic checksum of a file, e.g. the SHA-256 hash. This can be used to verify file integrity, so long as you have a reliable source for the hash. ...
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4answers
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How quickly can these password schemes really be beaten?

If you use a quick hashing algorithm like MD5 or SHA-1 to hash passwords and you don't use any salt at all, how quickly could one expect a hacker to find my password out? If I use a truly random salt ...
19
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4answers
5k 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 ...
3
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5answers
418 views

Am I required to hash passwords

Is one required to hash passwords by law in the US or elsewhere? If not required by law, are there legal ramifications if unhashed passwords are stolen? If not required in the US, but required in the ...
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3answers
7k views

Which SSL/TLS ciphers can be considered secure?

The OpenSSL website provides a long list of different ciphers available for SSL and TLS. My question is, which of those ciphers can be considered secure nowadays. I am especially interested in HTTPS, ...
11
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3answers
1k views

What is a good enough salt for a SaltedHash?

Since I'm hashing all passwords with each their own salt, is there a benefit to the salt being really random, or would an incremental counter or a guid be good enough? Also, is there a benefit of ...
3
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1answer
109 views

What are the implications of omitting the username in Secure Remote Password's verifier?

I consider implementing a Secure Remote Password (SRP-6a) verifier that omits the username from the x key hash. The intention is to allow authentication with multiple alternate user identifiers such ...
3
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2answers
355 views

What is considered a reasonably high iteration count?

I copy-pasted a function that implements the PBKDF2 hashing algorithm in PHP. The function asks for the amount of time that I would want it to loop in order to produce a hash. Now, I'm wondering, ...
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3answers
61 views

Patient Hashes for Compression and Security

Are there any front-running approaches to using server-generated hashes to encapsulate patient condition in a concise manner while maximizing security? For example, a system to represent current med ...
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4answers
8k views

Why AES is not used for secure hashing, instead of SHA-x?

As far as I understand, AES is believed to be extremely secure. (I have read somewhere that it would certainly not be broken in the next 20 years, but I am still not sure if the author was serious.) ...
2
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1answer
198 views

How do we encrypt a password using another password?

Heys all I've got a nub question, I was wondering What does it mean to encrypt a password using another password? For example I want to encrypt a password foo using a password bar, does it mean that ...
8
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1answer
416 views

Cheap to validate yet expensive to compute hashing algorithm

I am looking for a hashing algorithm somewhat like bcrypt, except that I would like validation to be extremely cheap. As an anti-spam measure I would like to require my clients spend say, half a ...
3
votes
4answers
212 views

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.
2
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3answers
1k views

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
1k views

Cryptographic Security of Dynamically Generated, Non-Random Salts

So when it comes to security, when I have an idea that seems good, but no one else seems to be doing, I try to assume that I'm overlooking something obvious or otherwise significant. This is one such ...
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3answers
978 views

Is it safe to use different derived keys but from the same passphrase for AES CBC encryption followed by HMAC SHA256 hashing?

I am working on a cross platform (JS/iOS/Android) list manager application that persists data through a REST API and I want to ensure that any textual data is properly encrypted on the client side so ...
8
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4answers
2k views

Is using HMAC to transmit a password OK?

I'm writing a small webapp and I don't want to transmit login passwords as cleartext. As I don't have SSL available I've written a one-time challenge system which sends a random string with the login ...
14
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2answers
651 views

Trustworthiness of kernel.org post attack

What are the security implications of the compromise of kernel.org on the trustworthiness of the code base hosted on the site’s Git repository? The announcement today explained the mitigations ...
18
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3answers
2k views

How would you store a 4 digit pin code securely in the database?

I'm familiar with password hashing, using salts, bcrypt etc. But it doesn't seem like this would work to store a 4 digit pin code since the attacker could try all 10,000 combinations quite quickly. ...
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2answers
4k views

Pre-hash password before applying bcrypt to avoid restricting password length

Good practice is not to unnecessarily restrict password length, so that appropriately-long passphrases (perhaps 35-45 chars for 6/7 dicewords) can be used. (See e.g. Should I have a maximum password ...
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1answer
508 views

Any risk in using the same salt for several hashes on a user?

Right now I'm storing a salt and password_hash on the users table (pretty standard stuff). The need arose to get a secure hash of another field for a user. Is there any risk in reusing the same salt ...
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2answers
3k views

Is “real salt” the same as “initialization vectors”?

In the question about real vs. fake salt, the answers describe how real salt 'perturbs the encryption algorithm.' I know roughly how initialization vectors work; is this the same concept, or something ...
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7answers
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“Real” Salt and “Fake” Salt

During a Q&A period at DEFCON this year, one member of the audience mentioned that we're using "fake salt" when concatenating a random value and a password before hashing. He defined "real salt" ...
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1answer
357 views

What did Blackberry do wrong?

The NIST defines a vulnerability in RIM Blackberry encryption discovered last October. Apparently, Blackberry's flavour of PBKDF2 was weak. They say: The offline backup mechanism in Research In ...
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8answers
754 views

Is the following authentication scheme secure?

I was trying to design an authentication system that would make it much harder to guess a password via brute force, and reduce the risk to a user if the hashed password was stolen through a snooping ...
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2answers
323 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 ...
32
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3answers
1k views

Am I wrong to believe that passwords should never be recoverable (one way hash)?

I recently forgot my password for our cable provider online account, only to discover that they sent it to us via plain text in an email. I quickly sent an email to customer support asking them if ...
3
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1answer
262 views

self-signatures using SHA1

This page says: self-signatures must not use SHA1 You can check this by doing: gpg --export-options export-minimal --export <keyid> | gpg --list-packets |grep -A 2 signature|grep ...
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15answers
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Why do people think that this is bad way to hash passwords?

Well, please tell me, what's wrong with this code: $password = "hello"; $password = md5($password); for($i=1;$i<20;$i++){ $password = md5($password); } It's exactly the same as this one: ...
3
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1answer
502 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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2answers
2k views

What are the most common password salting methods?

I learned that the Sun guys used the login name as salt for password hashing. Is this a common approach? What are the most common salt values?
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4answers
457 views

Hash/Digest of string; multiple clients and reverse lookup must be impossible

Ok so i need a technique (could be a system or just an algorithm) to generate a hash/digest of a string on a client app without me (admin of a server app) being able to determine what the original ...
7
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2answers
947 views

How difficult is it to modify an ISO image and still have the old md5 check sum?

If I want to download the ubuntu11.04.iso then: UBUNTUMIRRORSRV -> ISP -> ISP -> etc. -> MYPC I just want to ask that how difficult is to spoof the original MD5 sum (e.g.: the md5sum would be ...
6
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2answers
645 views

How do I use Skein's Stream Cipher?

I understand the NIST hash function competition candidate Skein comes with a built-in block cipher, Threefish, that is turned into a stream cipher by using Unique Block Iteration chaining (is that ...
6
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2answers
691 views

Is it better to hash n*x times in sha1 or n times in sha512 on the client side?

I already know I"m going to hash the user's password n times in either sha512 or n*x in sha1 before it is sent to the server. Once at the server, I'm going to use bcrypt set to use ~1/100th of a ...
5
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4answers
556 views

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 ...
4
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2answers
5k views

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'; ...
14
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2answers
953 views

Salting password with the first 8 bit of the password itself

Do you guys think salting password with the first 8 bit of the password itself will have same result as using stored salt to hash password? [Clarification] I am not storing salt but creating from the ...
6
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3answers
838 views

chosen plaintext attacks against MD5 and SHA1

According to http://tools.ietf.org/html/rfc2617#section-4.9, having the server chose a nonce but not having the client chose a nonce opens up Digest Access authentication to chosen plaintext attacks. ...
7
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4answers
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when people say a file has a checked md5 hash, what exactly does that mean?

ok I was just reading this site: http://www.zdnet.com/blog/bott/stay-safe-online-5-secrets-every-pc-and-mac-owner-should-know/3542?pg=4&tag=mantle_skin;content and thought of something I always ...
10
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2answers
885 views

Is there any advantage of bcrypt over multiple iterations of SHA-x/MD5?

I know that a good password hashing algorithm should be slow. MD5, SHA256, etc. are fast. So I've been adding multiple iterations of SHA-256 hashing to my web apps (around 50000). Getting the hash of ...
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3answers
1k views

What's the mathematical model behind the security claims of symmetric ciphers and digest algorithms?

Why can SHA-1 be considered a secure hash function? That's something I still wonder about. I understand the concepts of why modern asymmetric algorithms are deemed to be secure. They are founded on ...
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479 views

What is gained by hashing the last block on-device?

Recently I encountered the notion of "hashing the last block on-device". It means that when computing a digital signature, the hash that serves as input for the actual signature computation is not to ...
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3answers
402 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 ...
5
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4answers
994 views

Using password hash as session ID?

For a rich client web app, on the server I need to verify that each call comes from a legally logged in user. Obviously user ID is not enough, because that's easy to guess. I have an idea I am ...
15
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4answers
1k 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 ...