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 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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Why does some popular software still use md5?

Nowadays no one dares to defend md5 for any use, and of course they should not! However, much popular software still uses md5 in applications such as password hashing (although it's not simple/plain ...
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902 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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2answers
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Why are GPUs so good at cracking passwords?

What is it about GPUs that lets them crack passwords so quickly? It seems like the driving force behind adopting good key-derivation functions for passwords (bcrpyt, PBKDF2, scrypt) instead of ...
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2answers
757 views

Does it make any difference of the order Hashing and Encrypting in terms of security?

I am implementing a password vault program with java. I have programmed a triple DES for encryption and a SHA256 for hashing. My question is would it make any difference if I first hash the raw data ...
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Increase the security of an already stored password hash

Right now we're using 1024 byte PBKDF2 with 256 byte user-specific salt and variable iterations. However, I would much prefer to be able to, perhaps once every year or two, to be able to flat out ...
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2answers
159 views

Should hashing hashed hashes colide or not?

Since key stretching basically boils down to hashing hashes over and over again (where salt, pepper and password individualize the hash function, but the principle remains the same), I wonder about ...
2
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1answer
678 views

Improving Digest Authentication using PBKDF2

For a variety of reasons, I need to use digest authentication for a REST server that I have created. I have come up with an "improvement" that I believe strengthens the algorithm against MD5 attacks ...
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2answers
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what is the difference between a mac and a digital signiture

I understand that a MAC algorithm takes a message and a private key as input and hashes them to a value. I understand that senders and receivers often use MACs to authenticate a message and check the ...
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4answers
543 views

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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464 views

Client-Side Hashing to decrease value of password guessing heuristics

Yes, this is 'yet another client-side hashing' question. But, don't leave yet, I think there is some value here. I'd like to do something to mitigate the affect on the community as a whole when my ...
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Why we use GPG signatures for file verification instead of hash values?

for example here they put a gpg signature to verify what you download is what they really made. but why they just don't put a SHA256 hash value ? because its much more faster to check it and sometimes ...
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553 views

How high is the entropy of this salt-generating code? (No code-reading actually necessary)

What is the best method? Assumption: I have a function that generates a number of medium-high entropy bytes Step1: I generate 3 of these medium-high entropy bytes. Step2: I hash these bytes using a ...
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1answer
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Key length and hash function in PBKDF2

On this page: http://www.ruby-doc.org/stdlib-2.0/libdoc/openssl/rdoc/OpenSSL/PKCS5.html they make a statement that strikes me as rather weird: Key Length Specifies the length in bytes of ...
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2answers
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File security when encrypting files directly with the openssl command / and what about SHA1 hashing password first?

I've been using this command to encrypt files for a while now: openssl aes-256-cbc -a -salt -in secrets.txt -out secrets.txt.enc Then I type in a password. Can someone tell me, roughly speaking, ...
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1answer
306 views

Legality and ethics of cryptanalysis on password hashes

I'm working on my dissertation concerning cryptanalysis on password hashes. I'd like to delve into the legal and ethical aspects of cryptanalysis, however, seeing as I'n not at all well versed in law ...
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2answers
655 views

How to proceed if a new hash algorithm for passwords is introduced?

I have an e-mail address at a certain institution. A few days ago they sent me an e-mail (in German), which I'd like to paraphrase without revealing the institution: Dear Madams and Sirs, a ...
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5answers
4k views

Can I determine which algorithm was used if I know the matching hash of a given input?

If I know original text "12345" which encodes to "Tut0nlFFZ9sLVhPE5x81lQ==", how I can identify hashing algorithm?
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1answer
98 views

What is the purpose of the hashcode used in Exchange OWA HTTP requests?

This blog describes the URLs that are used in OWA and webservices. It also says that there is a hashcode that is used in conjunction with the throttling policy. Is this hashcode responsible for ...
3
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2answers
276 views

Confidentiality and integrity for web session

When the client authenticates with our service, he is issued an opaque "token". This token includes the information, that identifies the client and some other information about the client ("payload"). ...
3
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5answers
1k 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 ...
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5answers
2k views

What is the point of hashing passwords?

Even when following strict security protocols, and what the user typed is (in this hypothetical situation) completely impossible to derive, the key that the server needs to compare to is still there. ...
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Cracking MS-CACHE v2 hashes using GPU

As most people here will know, Windows caches domain/AD credentials in a format known as MS-Cache v2. Obviously, these would be excellent passwords to gain during a penetration test when local access ...
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2answers
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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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Database hash for password field [duplicate]

I'm using a mysql database and am looking for a cryptographic hash method for a password with salt added to it. What would be the best hash method for this problem?
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1answer
980 views

sha-512 vs sha-3? [duplicate]

Does the new SHA-3 Keccak hashing algorithm offer any benefits from SHA-512? "Even worse, none of the SHA-3 candidates is significantly better. When SHA-3 is announced, I'm going to recommend that, ...
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1answer
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Using John the Ripper to crack SHA hash w/ partial knowledge

Group, I have a SHA1 hash that I would like to brute-force. I have knowledge of several characters before and after the password (ie, if the hash is derived from "xxxpasswordyyy", I know both xxx and ...
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Secure transmission for desktop applications

Suppose I have a desktop application that does password hashing for login authentication. Is the password normally hashed before it travels to the wires or does it travel to the wires first in plain ...
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2answers
285 views

Creating a rainbow table with predefined text

I need to extract a password from a hash. This hash was generated by prepending and appending two different predefined strings to the password: Hash(PredefinedString1+Password+PredefinedString2) ...
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2answers
605 views

What is this hashing algorithm?

I need to authenticate against another programs user credentials to allow access to a second tie-in system. I am having trouble figuring out what hashing algorithm is being used by the first program ...
3
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2answers
319 views

Fixing the high-bit problem in PHP's crypt() implementation

I'm working on a site that has to have compatibility with older versions of PHP, which suffer from a high-bit issue in the Blowfish crypt() implementation. Essentially, non-ASCII characters are not ...
0
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1answer
628 views

Determine hashing algorthim only with known input and output

Given the input: test A system generates the following output hash: 0x001F41B6A0534D3B851D69EFE6237F550100000010D5F4FC65E64BCFDBF2590212E4411C44942C6C734C00ACFE13B958DCAB3614 I do not know ...
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4answers
779 views

Is using the md5 hashing algorithm as method for authorization in an HTTP POST request unsafe?

I am creating a page on a website that will show a user some authorized information from another website, and that website uses a combination of the user's user-number and a secret passphrase hashed ...
2
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1answer
718 views

Loki How to crack the password hash OSPF?

I have created for myself a lab of routers in GNS3 . Routing protocol between routers is OSPF. Now,by Loki penetration testing, I found that routers are the feature authentication. Using wireshark, I ...
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3answers
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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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2answers
175 views

Easy protocol for email authentication

I'm cooking up a very simple system to send commands to a remote server via email. Everytime an email is sent to do_something@mydomain.net, the server runs a python script that does something ...
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2answers
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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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2answers
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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 ...
3
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1answer
1k views

I've heard that salt is not meant to be secret, but what if I made it secret? [duplicate]

Possible Duplicate: Password Hashing add salt + pepper or is salt enough? How to store salt? Ok I have been studying a lot about password hashing lately. And I have a few questions. So I ...
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3answers
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Content hashes to help protect resources being fetched from a CDN

During a conversation in The DMZ, it was suggested that an SHA256 hash could be used to check that content being delivered from a CDN hasn't changed before being executed, similar to how Kim Dotcom's ...
3
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2answers
284 views

is it easier to get the original password if you have multiple hashes of it?

Most users tipically use the same password for multiple applications. Let's say all of these applications hash the password in some way. Would it be easier for an attacker to get the original password ...
2
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1answer
229 views

Can a salted hash be an effective MAC?

An HMAC is basically a "keyed hash". Only the correct message and the correct key will produce a particular hash digest efficiently. Conceptually speaking, the same can be said for a salted hash; ...
3
votes
0answers
282 views

Can an attacker guess my password length from a hash? [duplicate]

Possible Duplicate: Possible to detect password length from hash? Is doubling your password adds more security? Considering I do not provide him any personal information relating to it, are ...
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6answers
1k views

Is SHA-1 encryption?

I have read that SHA-1 is a cryptographic hash function. On an exam, SHA-1 was given as a possible one-way encryption algorithm. Does SHA-1 require a key as input? Is a key required to qualify as ...
4
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5answers
706 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 ...
7
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3answers
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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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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 ...
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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 can I extract the MD5 hash of a password protected MS Office Word 2000 document?

AFAIK, the compound file format identifier is D0 CF 11 E0 A1 B1 1A E1, which is located in the offset 0 of the header, which has a length of exactly 512 bytes. However that is not enough to get the ...
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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 ...