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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5
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2answers
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When can you not use strcmp?

I've read that one shouldn't use strncmp(userSuppliedPassword,origPassword,sizeOfArray) (or String.equals in Java) since one can use a timing attack to guess the password. Rather, one should use a ...
17
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4answers
7k views

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 ...
394
votes
5answers
136k views

Do any security experts recommend bcrypt for password storage?

On the surface bcrypt, an 11 year old security algorithm designed for hashing passwords by Niels Provos and David Mazieres, which is based on the initialization function used in the NIST approved ...
5
votes
1answer
2k views

Are there any ways to leverage NTLM V2 hashes during a penetration test?

I am on a penetration test at the moment, where LM/NTMLv1 hashes are disabled. I have captured a number of NTLMv2 hashes via NBNS spoofing, however was unable to crack them after running them through ...
17
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4answers
2k views

Why would a website serve different versions of a file over HTTP and HTTPS?

Here is a link given on curl's official website: (prefix omitted) bintray.com/artifact/download/vszakats/generic/curl-7.46.0-win64-mingw.7z When I downloaded it with prefixes http:// and https:// I ...
1
vote
2answers
222 views

What if the Local Windows Cert Store is Compromised?

The diagram below illustrates chaining digital certificates up to a publicly trusted Root Certificate: I have been researching how trusted root authorities (such as GlobalSign or Verisign) are used ...
3
votes
2answers
200 views

Hashing password multiple times with different random salts

I have read a lot of answers about this topic like: https://programmers.stackexchange.com/questions/115406/is-it-more-secure-to-hash-a-password-multiple-times. https://stackoverflow.com/questions/...
0
votes
1answer
28 views

First string in hash collisions bucket

My understanding of hashing is conceptual at best and I'm assuming things that I'm not sure of and it leads me to a question that I don't even know if it's founded or not. So please correct my ...
5
votes
1answer
122 views

Random string vs hash(random string)?

I'm implementing a one-time token service. Each of these one-time token represents some server side data/action associated with it (a 'email confirm' action for example), so that my web service can ...
3
votes
2answers
100 views

Sign a callback URL

I have a Single Sign-On system that works this way : User clicks link on clientsite.com that redirect him to mastersite.com?returnTo=http://clientsite.com If auth is valid, the user is redirected ...
0
votes
2answers
280 views

Is this hash function safe?

Below is the hash function implementation of the roguewave library. It returns a 32 bit hash. The core operation is A = B ^ ((C << 5) | (C >> 27)). Is this hash safe to use as a password check ...
-1
votes
1answer
67 views

Is there any kind of encryption that returns constant number of characters?

I wonder if there is any kind of publicly known encryption (not hashing) algorithm that generates constant number of characters independent of the input. I have came across an online platform that ...
3
votes
1answer
435 views

John the ripper is not identifying hashes

I'm attempting to use JTR against a password protected zip. I have created the hash file using:zip2john filename.zip > filename.hash and i get a successful output:file.txt is using AES encryption, ...
5
votes
1answer
604 views

Is it bad to add a guessable password to a random password?

Let's say a person has a password they used before they knew about how to make good passwords, like peter123. Let's also say that when they were thinking of a better password, they found they could ...
1
vote
0answers
47 views

trapdoor information with hash functions

I have been playing with an idea for the past few days. I have been unable to find information on here or crypto.stackexchange about using trapdoor information in the input to a hash function. ...
4
votes
1answer
87 views

Unable to get correct base for cracking Crypt3 SHA-512 on Linux with Python

I am reading a book and it gives me a simple Python script to crack /etc/shadow passwords that were encrypted with the crypt() function. It then challenges you to amend the Python program to work with ...
17
votes
2answers
4k views

Insecure versions of crypt hashes

I read at crackstation not to use these variants of bcrypt* ($1$, $2$, $2a$, $2x$, $3$),but I've used bcrypt ($2a$) in various sensitive implementations recently. Can any security expert clarify why ...
0
votes
1answer
223 views

hashcat hash type, convert sha256 binary to hex

I am attempting to use hashcat to crack a hash that is 32 characters in length. I know the hash is sha256. When i run the following command hashcat -m 1400 binary-hashfound.txt /path/to/rockyou....
50
votes
13answers
6k views

Sequential identifying string that can't be reverse engineered (the “invoice number” problem)

Let's say I operate a website where you can create cat pictures. I give every cat picture a unique identifier so that it can be shared on social media with http://catpictures.com/base62Identifier. I ...
6
votes
2answers
131 views

If no maximum length is placed on a password, can't collisions occur?

As I was thinking about storing password hashes in a database, it dawned on me that there might be hash collisions if there is no set maximum length for the password being hashed. My understanding is ...
2
votes
3answers
1k views

Key stretching a hash

If I implement a function which hashes the first half of my password with MD5 and the second half with SHA-2 and MD5, is there a security issue when I put these two hashes together to create a 64 ...
3
votes
0answers
183 views

Login details security using salt and hash, and a login role in postgresql

I am coding up the security for a website in express.js and postgresql database. Now I have been reading about salting and hashing and I have the code set up with pdkdf2 using the crypto module, but ...
1
vote
1answer
26 views

One Input Two Hashes

Suppose I have some password x, and two different hash functions h1 and h2. I can then compute the hash y1 = h1(x) and y2 = h2(x). Is there any sort of vulnerability in this case? More specifically,...
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votes
2answers
61 views

How secure is a hash + reverse(hash)?

From what I know there is a method called salt added to hashes in order to prevent attackers from using pre-computed hashes. As long as the attacker can find a static salt in reverse hashing and do a ...
8
votes
3answers
824 views

Downloaded file checksums

More than often next to the download button of a file there is a variety of checksums. When I download a file what security risks am I exposed to if I don't check for its integrity?
20
votes
6answers
4k views

Can any password hash ever be secure?

My understanding is the the main reason MD5 is insecure, is that it can be calculated too quickly, allowing too many attempts to be tried. People recommend instead using a hash that has been designed ...
1
vote
0answers
62 views

Token-based authentication for specific requirement

We have the following requirement for creating a token in .NET to be used in providing a challenge token and an actual authentication (auth) token. The auth token will then be used to authenticated ...
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votes
1answer
86 views

Unconditionally Secure Authentication

I'm trying to add the authentication for my One-Time Pad implementation. I know that to provide Unconditionally Secure Authentication I need to use the One-Time MAC authentication. But I don't ...
34
votes
4answers
4k views

Does every hash value have an inverse value?

There are many different hash functions, md5, sha, and others. They take a value V and produce a H via transformation Function(V) = H, where Function is md5, sha, etc. My question is: Does every hash ...
0
votes
0answers
35 views

Malicious node in distributed hash table (Tor)

I'm thinking about the DHT in Tor that is used to look up hidden services. Namely, if you were running a node in the Tor DHT system, 1) Could you realise that you were storing the data for a nasty ....
19
votes
2answers
2k views

How safe are signed git tags? Only as safe as SHA-1 or somehow safer?

How safe are signed git tags? Especially because git uses SHA-1. There is contradictory information around. So if one verifies a git tag (git tag -v tagname), then checksouts the tag, and checks that ...
2
votes
0answers
209 views

Securely storing users PIN on Android with fingerprint authentication

I am have an Android app where the user can enter a pin specific to a particular phone to save them entering the full password. I'm now looking at the new fingerprint reader API on Android M where I ...
0
votes
1answer
53 views

Software activation “by phone” [closed]

I'm a software developer, and I would like to protect my application in an offline way, like many software do activating by phone. Following a screenshot taken from google images on what I would like ...
0
votes
0answers
52 views

Generation of the primes p,q and g for DSA using an Hash Function in OpenSSL

We can generate primes p,q and g for DSA in OpenSSL by using command: openssl dsaparam -text -out dsaparam.pem 1024 Is it possible to generate primes p , q and g using an Hash Function in OpenSSL ...
26
votes
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
votes
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 ...
352
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
324 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
77 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
226 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
236 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
160 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
235 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
67 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
2k 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
66 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 ...