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 this kind of authentication scheme called?

In the past I've heard about a scheme to prove your identity online in places like forums, without having to create an account. When posting, the user would enter a password which is then heavily ...
4
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4answers
304 views

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 ...
13
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7answers
994 views

Why should I hash passwords?

I've read that every good web application should hash passwords. I found many articles about hashing. So I started implementing hashing on my website and then I asked myself why should I do it? When a ...
5
votes
4answers
2k views

SHA-512 unix passwords. How secure are those hashes, really?

I came across this very alarming sounding thread which indicates a GPU with about half the compute capacity of the GPU currently powering the monitor I type this on is capable of 11.5k c/s. I'm not ...
2
votes
1answer
613 views

How to save the random salt to the database

As I understand it, salting and hashing passwords is the way to go. I also understand that to authenticate a salted and hashed password, the random salt needs to be saved. Does this mean that if I use ...
5
votes
5answers
831 views

Is it a good idea to use an input by the user as SALT?

I have read many Q&As here on IT Security about password hashing and salting. I am building a simple registration form for our community website which will be used by our members to create their ...
5
votes
2answers
125 views

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 ...
4
votes
2answers
623 views

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 ...
-3
votes
3answers
846 views

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 ...
1
vote
1answer
144 views

Generate Keytool Object from CSR

I have to develop an application which uses another application for generating a CSR. After generating the CSR I have to provide this CSR along with a SHA256 hash of the public key to a CA. The ...
7
votes
4answers
2k views

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 ...
32
votes
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 ...
5
votes
3answers
1k views

How exactly is MD5 vulnerable to collission attacks?

I've often read that MD5 (among other hashing algorithms) is vulnerable to collisions attacks. I understand the collision part: there exist two (or more) inputs such that MD5 will generate the same ...
0
votes
1answer
215 views

What does it mean by the 'Hash of a malware'?

I have just recently started to delve into the topics of malware. In my hunt for malware binaries, I came across certain responses that it is not easy to grab binaries based on malware names like ...
0
votes
1answer
469 views

How do I generate a blowfish password hash in Ubuntu?

What's the command line to generate a blowfish password hash? I can't seem to figure this out at all. Apache's htpasswd only supports bcrypt, and openssl passwd doesn't even do blowfish hahes (but it ...
3
votes
6answers
953 views

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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2answers
2k views

How to get an NT hash from registry? [closed]

I want to manually get the NT hash from the registry (without any tool). Let's say just for the administrator. I know that it must be stored in the SAM area of the registry somewhere so I tried to ...
22
votes
3answers
28k views

Is SHA1 better than md5 only because it generates a hash of 160 bits?

It is well known that SHA1 is recommended more than md5 for hashing since md5 is practically broken as lot of collisions have been found. With the birthday attack, it is possible to get a collision ...
2
votes
3answers
641 views

Reversing Password Hashes [duplicate]

if someone got hold of the hashes of all passwords for a website, how do they 1) get passwords from the hashes. As far as I can tell from searching the internet everything seems to say do a dictionary ...
6
votes
1answer
204 views

HKDF and key stretching

I thought that all key derivation functions would do a key stretching phase, by iterating some kind of process. But I can't see that process in HKDF. HKDF doesn't do key strengthening? If I have a ...
2
votes
5answers
191 views

Methods used to reverse a hash

I know that a hash is a one-way-function and that therefore there isn't a reversal function. By reversing a hash I just mean to find some plaintext that gives the hash. I think that I understand that ...
2
votes
1answer
432 views

What are realistic rates for brute force hashing?

I'm trying to gauge password strength assuming that the attacker has a hash of my password. Can anyone cite some realistic contemporary rates at which someone could perform various hashes? I know most ...
2
votes
3answers
347 views

Storing passwords on a home computer

I remember all the passwords (and variations of passwords) that I use for various sites online. The problem is not that I forget a password, but that I forget which password goes with which site. And ...
3
votes
2answers
104 views

How to ensure two messages are from the same party

I need to verify that two messages, that came over distinct channels, come from the same origin: without knowing anything about the origin beforehand the channels are one-way, only one message may ...
7
votes
2answers
4k views

Safety of publishing last 4 credit card digits in age of fast computing?

How safe is it to make public the last four digits of a credit card? Credit card numbers have a specific format. Digits tell you what type of institution issued the card, what bank issued the card, ...
9
votes
6answers
3k views

Is MD5 considered insecure?

After all these articles circulating online about md5 exploits, I am considering switching to another hash algorithm. As far as I know it's always been the algorithm of choice among numerous DBAs. Is ...
-1
votes
1answer
186 views

After salting my passwords, are they protected against dictionary attacks? [duplicate]

I use sha1() to hash my users passwords, but recently a friend told me that if someone get the hash then they could use dictionary attack and he recommended using salts. I implemented a random salt ...
20
votes
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, ...
2
votes
3answers
394 views

Why are MD5 collisions dangerous?

I understand that the MD5 algorithm isn't collision resistant, and that collisions between data of arbitrary size can be found with more efficient methods than brute-forcing. However, I have read ...
50
votes
5answers
10k views

Is sending password to user email secure?

How secure is sending passwords through email to a user, since email isn't secured by HTTPS. What is the best way to secure it? Should i use encryption?
2
votes
3answers
114 views

User specified iteration count

I'm working on a PHP authentication and registration system following the standard salt+password = 'auth hash' and using the plaintext/unencrypted username as the lookup field on the initial query. ...
5
votes
2answers
285 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 ...
3
votes
0answers
242 views

Similar passwords can't be used again. A sign of unhashed password storage? [duplicate]

In my school everyone must change their password every six months. The new passwords cannot be the exact same as the old one, this make sense, however many of my peers often complain that they need ...
0
votes
2answers
718 views

Why store the password salt instead of generating it? [duplicate]

So, reading through this article: http://crackstation.net/hashing-security.htm it says that storing the salt is fine in plain text because it renders the lookup/rainbow tables ineffective. I get that, ...
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votes
1answer
154 views

Properties for cryptographic hash functions (preimage, second preimage and collision resistant)

While studying computer security at university I have been asked this question: There are three desirable properties for cryptographic hash functions: Preimage resistant, Second preimage resistant, ...
7
votes
2answers
414 views

Does the md5 (or any hash for that matter) of a string include the null terminator?

Does the md5 (or any hash for that matter) of a string include the null terminator in its calculations? That is does the hash of a string equal the hash of the sequence of bytes that represents the ...
0
votes
0answers
31 views

How can I determine the encryption used by knowing input and result? [duplicate]

Is it possible to determine the encryption or hash used if I know the original input and final output? There is a similar post here: Determine encoding/hashing methods used based on knowing the input ...
8
votes
1answer
834 views

“Official statement” on php.net : CRYPT_BLOWFISH is strongest hash algorithm. Why?

First: I asked this question on stackoverflow and was kindly asked to post this here again. See the original question here. According to the [early] doc pages of the new PHP 5.5 password ...
4
votes
3answers
10k views

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 ...
5
votes
2answers
574 views

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.
2
votes
2answers
151 views

Does glibc2 version of the crypt function still use DES for alternative hashing methods?

I'm trying to understand how typical Linux distributions generate the password field for entries in /etc/shadow. I can't figure out what encryption algorithm is being used to produce the encrypted ...
-1
votes
3answers
181 views

Salting in encryption (rather than hashing)

I am aware of the benefits of adding a salt to values that are hashed using a one-way function. Is adding a salt to a value that is being encrypted (using symmetric encryption) considered to be good ...
29
votes
7answers
6k views

Is salting a hash really as secure as common knowledge implies?

(I did search on this topic, but I found no complete question/answer that addressed it, or even good portions of questions that might be relevant.) I'm implementing a salt function for user passwords ...
3
votes
4answers
313 views

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 ...
2
votes
1answer
241 views

What is the collision chance of a 128-bit hashing function if it is always fed with 256-bits of data?

I mean "normal" collisions not based on any attack. How do i calculate it?
4
votes
1answer
126 views

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 ...
5
votes
1answer
189 views

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 ...
1
vote
1answer
920 views

How secure is my private key in the Windows Digital Certificate store?

Many files we download don't have digital signatures. Files may get infected or someone may intentionally modify them on our hard disk. So I wrote a simple file hashing program in c# that creates a ...
0
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3answers
316 views

Why one time passwords using nested hash chain are not used?

I am wondering, why web sites do not use one-time passwords generated by hash chain. By that I mean that a client chooses a secret and after being salted, he applies some secure hash function F() on ...
3
votes
5answers
717 views

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 ...