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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Why is the diffusion property important in hash functions

I have always heard that A change in just one bit of the original text shall change half of the bits of its hash. I think this property is called the diffusion property. However, I wonder why ...
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1answer
178 views

Stripping / appending characters from user password before hashing to conceal it forever?

I had this idea to permanently conceal user password by requiring minimum length then stripping certain characters. For example if the user password is secret123, the system will strip it down to ...
3
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1answer
379 views

Cookie based session variables

I have a situation in which I cannot use a server-side session, but must allow users to log in, and for their logged in state to be persistent between queries. As with anything that involves crypto ...
5
votes
4answers
6k views

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 ...
19
votes
4answers
3k views

Why is using salt more secure?

Storing the hash of users' passwords, e.g. in a database, is insecure since human passwords are vulnerable to dictionary attacks. Everyone suggests that this is mitigated via the use of salts, but the ...
12
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4answers
1k views

Encrypting IP addresses in a MySQL database

I'd like to encrypt IP addresses in my MySQL database, with the following constraints: Does not need to be resistant to attackers that can execute queries. Must be resistant to attackers that have ...
1
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1answer
297 views

How to check for a key *and* store encrypted data?

I wish to create a system wherein I store encrypted data. Users can access this data if they have the key. If they give a wrong key, they don't get access at all. If they give the right key, they get ...
8
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2answers
1k views

Authenticated Encryption vs. contained and encrypted checksum/hash?

So I read through http://en.wikipedia.org/wiki/Authenticated_encryption and http://www.cryptopp.com/wiki/Authenticated_Encryption and I don't seem to be following the concept. From the simple ...
8
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6answers
815 views

Does repeating one word to form a password result in a similar pattern in its encrypted format?

If i use a single word to form a password by repeating it like the examples below: securesecuresecuresecuresecuresecure SeCuReSeCuReSeCuReSeCuReSeCuReSeCuReSeCuRe ...
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3answers
1k views

Hashing length for storing password

Does larger hash size improve the security? Is it overkill to use 512 bit hash? If I stored only 256 bits of the PBKDF2-SHA512 derived key, is it less, equal or more safe than 256 bits of ...
3
votes
2answers
374 views

What algorithms can be used for device pairing?

I am to implement a system where android devices connect to a central server and have to register with different user accounts, so I have decided to create a pairing dance similar to what can be ...
0
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1answer
178 views

Securing communication

The problem: I have an open-source client (a Firefox add-on written in JavaScript) and a server containing somewhat sensible user information: username and user history (all from YouTube). The client ...
20
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5answers
3k 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. ...
3
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3answers
243 views

Does the hash change the security of the Secure Remote Password protocol?

I'm implementing the Secure Remote Password protocol, and similar to this question, I'm wondering if I can use the SHA-512 hash function instead of SHA-1 currently being used. Would this help improve ...
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votes
4answers
7k views

How to decrypt LDAP passwords Hashed as MD5? [closed]

I am doing a penetration test, and i would like to know if i can decrypt passwords stored in LDAP. i tried some sites decrypt MD5 , they give me error message tells that the input is not MD5. Could ...
2
votes
2answers
338 views

Is it secure to have one salt or generate and send it over the air?

To authorize user I'm sending salted hash over the air. My question it is more secure to obtain randomly generated salt (but send unencrypted), or have one salt on client (desktop application) and ...
40
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5answers
5k views

Password security in databases - today still best practice? [duplicate]

Possible Duplicate: Which password hashing method should I use? There are a ton of great posts about password security in databases on stack overflow and on other sites and as I am ...
3
votes
1answer
974 views

How to implement WSS UsernameToken when password on the server is salted and hashed?

I'm currently trying to write a web service for customer and requirement is to use WS Security. On their server side, they have passwords stored as SHA-1(salt+password). According to WSS spec, ...
4
votes
11answers
4k views

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 ...
21
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2answers
5k views

What is the difference between a Hash Function and a Cryptographic Hash Function?

I mean, is it just a matter of "how difficult is it to reverse the function with the current technology"? Or is there a mathematical concept or property that makes them different? If it is a matter ...
0
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3answers
556 views

DNS queries with hex string that is a SHA1 of a domain name! Is it a malware?

My computer does a lot of queries to strange domains such as: 56cea5c2b408989ab067adcb787d0f99209bbe07.mydomain.com The strange thing is that 56cea5c2b408989ab067adcb787d0f99209bbe07 is the SHA1 of ...
112
votes
11answers
25k views

Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it?

Why can't a password hash be reverse engineered? I've looked into this ages ago and have read lots on it, but I can't find the explanation of why it can't be done. An example will make it easier to ...
2
votes
6answers
997 views

“Double hashing” with 2 different hash functions

Is doing something like this sha256(sha512(password+salt)) Less secure then just doing sha256(password+salt) I've heard it will increase collision chances. I can think of 3 reasons to do this ...
0
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2answers
163 views

How much security should I use for my web application?

My question is, for a "normal" site, what do you think is enough to secure against methods used by "script kiddies"? For example, SQL injection, XSS, and stuff like that. Same question for password ...
7
votes
1answer
865 views

Would it make sense to use Bcrypt and PBKDF2 together?

I've read various opinions about whether Bcrypt or PDBKF2 is a better key derivation hashing method. The answer seems to depend on a lot of complicated factors that are not easy to analyze. Would ...
2
votes
4answers
318 views

sha512 as no-login-necessary token

My site has a news subscription system. When an item is updated, a notification email goes out to everyone subscribed to that item. You can un/subscribe via a form on each item's page. I wanted to ...
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2answers
1k views

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 ...
12
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2answers
3k views

How big salt should be?

I will be using scrypt to store passwords in my application. As such, I'll be using SHA-256 and Salsa20 crypto primitives (with PBKDF2). Having that in mind, how big salt should I use? Should it be ...
8
votes
5answers
2k views

What is the problem with chain hashing?

Let's say that my password is a single character: "a". Couldn't I chain hash it 1000 (or more) times and make it nearly invulnerable to rainbow table attacks and brute force? Why isn't this ...
4
votes
1answer
793 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 ...
5
votes
2answers
572 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 ...
4
votes
2answers
2k views

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 ...
10
votes
2answers
1k views

How does Google not care about “spaces” in Application-specific passwords?

I have recently setup "2-step verification" for my Google account. One of the features is the ability to create "Application-specific passwords " for devices that do not support the 2 step process. ...
8
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1answer
332 views

General purpose slow/unique hash routine for dup checking of private data, without storing the data itself?

I am wondering if there is a percentage of uniqueness known to be lost with every repeat of various hash routines, like MD5, SHA1, and how that might compare with other algorithms. If theoretically I ...
4
votes
2answers
4k views

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. ...
3
votes
3answers
312 views

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 ...
14
votes
7answers
2k views

Tripwire - Is it security Theater?

Tripwire type intrusion detection systems supposedly protect your system from rootkits, by monitoring the checksums of important binaries for changes. Let's say I have tripwire configured to run ...
4
votes
1answer
2k views

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 ...
5
votes
2answers
1k views

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 ...
6
votes
3answers
176 views

How could one detect if Apple/Google/etc. has modified a third party application distributed through their App Stores?

Are there any realistic methods for verifying that Apple or whoever has not tampered with third party application distributed through their App Store? You might for example have an open source ...
11
votes
4answers
4k views

Does symmetric encryption provide data integrity?

Let's say I have one server that encrypts a file with a symmetric key, e.g. AES-CBC, and sends it to clients that decrypt it. Does that provide data integrity when decrypted? Or is it possible for ...
5
votes
5answers
7k views

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?? ...
14
votes
1answer
2k views

Timing attacks on password hashes

Timing attacks can have a devastating impact in scenarios where the secret is involved, often in cases where byte-wise array comparison is used. Now there are those that advertise using constant ...
1
vote
1answer
1k views

Can Solaris' shadow hashes be created by better algorithms than the default DES-based hash?

By default, Solaris uses Traditional DES to encrypt password hashes in the shadow file. Is there a way to harden the security by changing this default behaviour and make it to be hashed using a ...
5
votes
2answers
2k views

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 ...
4
votes
2answers
193 views

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 ...
4
votes
3answers
917 views

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 ...
6
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3answers
747 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 ...
8
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2answers
747 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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votes
9answers
4k views

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 ...