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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26
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12answers
5k views

Can a file contain its md5sum inside it?

Just wondering if it is possible to create a file which has its md5sum inside it along with other contents too.
12
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1answer
1k views

Is Rfc2898DeriveBytes using HMAC SHA1 still considered “secure enough” for hashing passwords?

I've been told by a CISSP that the .NET class Rfc2898DeriveBytes would not pass a security audit today because it still uses SHA1. It's reliance on SHA1 - even with the iterations - leaves it too ...
350
votes
11answers
43k views

Is my developer's home-brew password security right or wrong, and why?

A developer, let's call him 'Dave', insists on using home-brew scripts for password security. See Dave's proposal below. His team spent months adopting an industry standard protocol using Bcrypt. ...
6
votes
1answer
316 views

Why would output from sqlmap be trimmed?

I've decided to learn sqlmap but having an issue with Sqlmap trimming some of my output, the hash. The hash is about to be 32 characters long but I'm only getting 25 and the warning: [WARNING] ...
1
vote
1answer
73 views

PBKDF2 constants

I recently found this PBKDF2 code: <?php /* * Password Hashing With PBKDF2 (http://crackstation.net/hashing-security.htm). * Copyright (c) 2013, Taylor Hornby * All rights reserved. * * ...
1
vote
1answer
215 views

Decoding base64 encoded message with a key [closed]

I am pentesting a database that where I found data which was base64 encoded. I tried the usual method of decoding base64, which didn't work. Later, I found in database a field called ...
2
votes
1answer
2k views

Is it fine to store single-use beta keys plain-text?

Is it okay to store single-use beta keys in plain-text in the database? I'll be pre-generating and storing about 2M keys. The keys get passed around so that people can sign up with it, rather than let ...
1
vote
3answers
228 views

Hash for secure file downloads? [closed]

Is there any hash structure that can be used for secure download of a file and validation of its contents? Looks like all hashes like MD5 are made for consistency check and are vulnerable to hash ...
-1
votes
2answers
128 views

Using a password hash…as the password? [duplicate]

Ok, this is probably a really stupid idea, but I can't really see why it would be a bad idea. Maybe someone can enlighten me. Why couldn't you enter a password good hashing algorithm like bcrypt, ...
0
votes
1answer
194 views

How can I detect if hashes are salted? [duplicate]

Is it possible to detect hash function of a hash if I don't have access to PHP code? I know that if a hash is some kind of MD5, but I don't know if there is salt etc.
3
votes
1answer
66 views

Does salt increase security if there is only a single hashed password?

Say there is only a single hashed password in the passwords file. If it was salted, would that make it more secure? My logic is: Yes because SALT helps protect against rainbow tables and dictionary ...
3
votes
2answers
2k views

What does GUID have, that a Whirlpool, MD5 or SHA-2 hash don't?

I'm trying to understand the use of GUID and what has always left me wondering is what's so special about them that I should consider using them instead of rolling my own type of unique ID. In other ...
4
votes
4answers
1k views

Can password_verify() be used to identify password after database breach?

I am a newbie to PHP and password hashing. I am following the instructions provided here to hash my user password before storing. My questions are: PHP recommends password_hash() method as a ...
5
votes
4answers
2k views

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 ...
6
votes
2answers
61 views

Is there an entropy difference between hashing an encoded string?

Of course if I apply (for example) SHA-2 to a base64 encoded string it will give me a different result versus the original data, but from a strength-perspective in terms of entropy, is there a ...
4
votes
4answers
163 views

Must an encrypted hash value be bigger than the password it was generated from?

I was reading a book called Introduction to network security theory and practice, and I found the following paragraph: Rainbow Tables A rainbow table is a table of two columns constructed as ...
2
votes
3answers
11k views

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 ...
8
votes
3answers
2k views

Is it easier to get the original password if you have multiple hashes of it, all created with the same hash function?

If you have multiple hashes of a password, all hashed with the same hash function, is it possible to use this to speed up retrieval of the original password in any way? (I found the question "is it ...
5
votes
1answer
977 views

Should I be worried about brute-forcing passwords that encrypts AES?

I am building an application that needs to locally store sensitive data, that is encrypted using the sha256 of a password provided by the user. It uses AES for encryption. I am worried that some ...
2
votes
1answer
81 views

Why hashing algorithms in layer 2 are weak? [closed]

It's known that hashing algorithms such as md5 and SHA1 are weak and can easily be cracked. I wonder why many layer 2 and 3 devices such as cisco switches still use weak hashing algorithms but don't ...
43
votes
5answers
28k views

How does hashing work?

I have been interested in Information Security. I was recently introduced to the idea of hashing. What I currently understand about hashing is that it takes the password a user enters. Then it ...
0
votes
2answers
16k views

If hashing is one way, why can we decrypt MD5 hashes?

I have read some times that hashing is a one way function, that is you can make the hash of a message, but you can't recover the original message from the hash, just check its integrity. However, if ...
5
votes
1answer
123 views

If I obtained a username and the salted password pairs from a server, can I login?

I am studying Salted Challenge Response Authentication Mechanism (SCRAM). According to the description at https://tools.ietf.org/html/rfc5802#page-8 it seems that the Client does not have to know ...
19
votes
8answers
3k 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 ...
34
votes
7answers
29k 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 ...
4
votes
1answer
281 views

How could a publicly available stream cipher (RC4) be kept secret so long?

I'm reading about the cryptographic function called RC4. Apparently, its method was kept secret from 1987 until 1994 despite being available to the public for licensing and use. How did it stay ...
5
votes
2answers
4k views

This is 2015. Has SHA1 been exploited or cracked yet?

went to Qualys SSL lab and tested one web site. One of the findings says the site is signed with weak algorithm SHA1withRSA and I did some research all are saying we should change to SHA-2. may i know ...
1
vote
2answers
108 views

Why is finding a strong collision only half the work of a weak collision?

Regarding hash collisions, an attacker only has to do half of the work to find a collision when they can control both messages compared to when they are trying to find a weak collision. This can be ...
0
votes
2answers
669 views

Why can't an n-bit hash be cracked by hashing every single n-bit plaintext?

I'm wondering why it's so hard to find collisions for cryptographic hashes. Take for example a hash function that outputs a 64 bit hash. In order to find collisions, if you feed the function every ...
3
votes
2answers
240 views

Why does LastPass store password hashes on the server at all?

While reading about LastPass' breach, I was wondering why would LastPass store strengthened password hashes at all on the server side? Could they only store the AES encrypted data and when the user ...
0
votes
0answers
80 views

Hashing Identifiers to Create Pseudonyms

I'm wanting to share datasets between two organisations in a pseudonymised way such that they link together via mutual entities (e.g. people) but so that the entities cannot be identified. E.g.: ...
2
votes
3answers
4k views

Proper hash_hmac key creation

I'm looking for, but unable to find, some definitive information on how long to make the secret and what characters are useable in creating a HMAC signature in PHP using SHA256. I found some ...
3
votes
3answers
246 views

Question regarding MAC and encryption

I was reading the chosen answer to the following question - "MAC vs Encryption" They say that just using encryption, "an attacker could alter the ciphertext to make it say something else when ...
0
votes
1answer
192 views

Is this a good hash function?

unsigned int hash(bytearray[] msg) { unsigned int hash = 0xDECAFEBAD; for(i = 0; i < msg.length(); i++) { hash = ((hash << 4) XOR (hash >> 28)) XOR msg[i]; } return ...
5
votes
1answer
100 views

Salting/Hashing a password

I don't have a security background, so I'm not sure on the best approach for this, I'm developing an android app which users will need to login to (all local). I'm going to store the password in a ...
3
votes
5answers
1k views

Should BCRYPT be used for client-side password hashing

I am concerned about the use of bcrypt for client-side password generation. I am developing a password generation function to be used client-side, similar to PwdHash and PasswordMaker. Much has been ...
2
votes
2answers
99 views

which encryption is used in this JS Variables

Which encryption method is used for these variable names: var g_license_info var g_server_time_obj Respectfully encrypted to: var ago05b4e111efe149737a67a177f00ffad2 var ...
4
votes
1answer
107 views

A predictable password generator for offline clients

I know this sounds like pretty dumb question. Why would you use a password generator at all if it's predictable. But suppose you have a server and client - the server always requires a password and ...
3
votes
0answers
113 views

How far should I go in protecting a user's SMBIOS UUID?

My server will be receiving data from several hundreds of computers. As part of keeping track of which computer sent what, I will be fingerprinting the hardware and keeping the results in my database. ...
4
votes
1answer
211 views

Why is Windows password security designed this way? [duplicate]

Let's start with the LM hash. The LanMan hash had MONUMENTAL security flaws, like the password being case insensitive (converted to upper), which reduced the keyspace for a brute force attack. On top ...
3
votes
2answers
186 views

How to give “Forgot password” option for a password encrypted file?

I have created a utility that encrypts a file (.txt, .dox, so on...). The utility asks for a password from user at the time of file encryption. Problem Suppose a user has created 1000 encrypted ...
5
votes
2answers
584 views

Why not slightly modify an existing hashfunction to create your own? [duplicate]

I read this interesting question on why improvising your own Hash function out of existing hash functions is bad. However this is specifically focusing on 'mixing' existing hashfunctions. What if for ...
5
votes
3answers
170 views

How to prevent a prophecy from becoming self-fulfilling or self-defeating

Let's assume that I have deduced with a high probability what a certain famous person or organization will choose to do at a near-future date. How can I publish any proof of me having deduced this? ...
1
vote
3answers
189 views

how to authenticate user in client-server implementation

So I am trying to implement a client-server application for sending files over SSL sockets. And I am trying to decide on a very secure design for authenticating the client. The server is going to ...
-3
votes
1answer
94 views

Hash regex for malware recognition [closed]

I'm looking to store two types of hashes for recognizing blacklisted code. These are the FireEye "import hash" (or imphash) and the ssdeep "fuzzy hash". Is there a regex (or formal documentation) I ...
1
vote
1answer
198 views

best practices for storing retrievable passwords

I am trying to build a NMS (network management system) and I am required to store passwords for 3rd party databases, devices and servers that are being managed (not user passwords). These passwords ...
5
votes
1answer
173 views

Distributed tokenization for credit card numbers

I have two locations within the same firm that hold credit card numbers. I want to be able to "join" on credit card number to do business analytics after transmitting card number-linked data from one ...
2
votes
1answer
145 views

What is a key-hardened hash?

I've seen the term 'key hardened hash' used to describe a recommended way to tighten up password hashing. What does this mean? Can it just mean to use a pepper?
2
votes
2answers
129 views

Best hash for indexing and searching encrypted data

I would like to be able to do database look-ups on a set of data based on one of the encrypted fields. My understanding of the best practice for accomplishing this is to store a hash of the data I ...
5
votes
2answers
613 views

How facebook knows my new password is too similar to my old password? [duplicate]

I am still very new to Information Security field and as far as I know, websites use hashing algorithm on user's passwords before storing it and they don't know the plain-text password of a user. ...