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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Is it safe to use different derived keys but from the same passphrase for AES CBC encryption followed by HMAC SHA256 hashing?

I am working on a cross platform (JS/iOS/Android) list manager application that persists data through a REST API and I want to ensure that any textual data is properly encrypted on the client side so ...
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644 views

Getting reliable checksums

Update: A version of transmission that contains malware has been distributed very recently. Quoting this ars technica article: It appears that somehow the Transmission website may have been ...
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215 views

How secure is Visual host key, and how is SHA2 converted into that representation?

SHA2 has 256 bits of possibilities. Visual host key seems to have the following upper and lowercase = 26*2 numbers and symbols = 20 Additional symbols = 22 Total 94 characters represented in ...
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927 views

Verify CDN javascript's integrity

CDNs speed up the loading of websites by allowing caching for frequently used javascript libraries like jquery. How do we know if they have modified the javascript before serving it to my clients? ...
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418 views

Is there any way to cryptographically hash a human thumbprint?

Is there any way to cryptographically hash a human thumbprint into a form that can be consistently reproduced by thumbprint readers? Assuming that it would be possible to create a database of ...
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574 views

Why is a CSR hashed?

What are the use cases for defining something other than the default SHA1 hash in a CSR? Is it to protect the digital signature, public/private keys? What is it protecting exactly?
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Should security phrases be hashed?

I didn't think of this before but today I just realised that in soke sites, pw recovery is possible if you know the answers to security questions like What is your mother's maiden name? In this ...
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229 views

Keyed-hashing a password with a hash of the password + salt as the key, is it safe?

I was looking at our authentication system which hashes passwords differently than I was taught. The salt is a constant byte array and it uses the password + the salt as a key for the password hashing ...
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363 views

Site allows both Partial and Complete password authentication; do they have my password in plain text? [duplicate]

My bank provides online banking facility like most of the banks these days. On the web they have Partial Password Authentication. Although I don't really believe in PPA providing extra security but ...
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How do we estimate the time taken to crack a hash using brute force techniques

A German hacker famously managed to brute force crack a 160 bit SHA1 hash with passwords between 1 to 6 digits in 49 minutes. Now keeping everything constant (hardware, cracking technique - here ...
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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.
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131 views

Why RSA signatures based on the hash of the message? [closed]

Why RSA signatures based on the hash of the message rather than the message itself?
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330 views

Why do file storage sites have a long unique id for their download links?

I'm creating a file storage site and what I would do is just have the download links format as: https://www.domain.com/[id]/[file name] //id would just be 1, 2, 3 etc. Dropbox and many others have ...
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About password_hash() in PHP and storing (part of) its salt outside DB

So, i learned that new in PHP 5.5 is password-hash() which works much like crypt(). Which is more secure (slower) than md5() or sha1(). The result string is algo+hash+salt, which can be passed as-is ...
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What is is the best way to create virus signature database? [closed]

We are thinking to develop a new Antivirus program. The main concern is to create a virus signature database. I want to ask what is the best possible way to add viruses signature in our database to ...
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624 views

How to store/encrypt fingerprint?

Storing password is a no brainer : use a password hasher. But.. How do you proceed to store fingerprints securely on your server? Meaning that even if your server and all it's data is stolen, someone ...
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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 ...
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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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Identifying an unknown hash

During some of my research work I encountered an unknown hashed string. What I am curious about is the algorithm used to generate it. A factor that makes it interesting - the string contains an ...
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Truncating the output of SHA256 to 128 bits

suppose we need/prefer 128 bit hash output. for example to generate a 128 bit encryption key or, in other applications (e.g. file integrity verifications), to consume less storage space. i don't know ...
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How should I choose a difficulty factor for my password hashing function?

Assuming that I'm doing password hashing properly and using bcrypt, scrypt or PBKDF2, how should I go about choosing an appropriate difficulty factor? i.e rounds for bcrypt, iterations for PBKDF2 and ...
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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 ...
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Implementing Secure Remote Password: Constructing the verifier

The SRP protocol as described in RFC 2945 generates the password verifier: x = SHA(<salt> | SHA(<username> | ":" | <raw password>))` v = g^x % N I have three questions: why use ...
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Random padding in hash functions

In this answer, it was recommended that you add random padding when hashing messages for a trusted timestamp, such as for predictions, in order to avoid dictionary and brute force attacks (at least ...
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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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Is there a table that compares hashing algorithms by speed, relatively (machine independent)

As far as I understood*, one of the major criteria when choosing a password / salt hashing algorithm is it's speed. To prevent brute force attacks, a slower algorithm is better (and also makes it more ...
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What is the best way to store passwords in OpenLDAP?

I would like to store user credentials in an OpenLDAP or similar directory server. A lot of online commentary about storing passwords in modern contexts recommends using password derivation schemes ...
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Hashed passwords for NTLM authentication

I understood that Windows users' password hashes can be exported very easily. Right? So my question is: If I can have the hashes of other user accounts (e.g. local users on my Windows machine), isn't ...
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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, ...
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Rainbow Tables: What is the Reduction Used for?

This is a follow up from this answer. The answer is very good, and it put me to thinking and doing some research. I have found another good explanation on this site. At some point, the author says: ...
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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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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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What is considered a reasonably high iteration count?

I copy-pasted a function that implements the PBKDF2 hashing algorithm in PHP. The function asks for the amount of time that I would want it to loop in order to produce a hash. Now, I'm wondering, ...
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Disallowing Similar Passwords [duplicate]

Upfront, I want to clarify that I am not a professional cryptographer, I am more curious about playing with the math and science behind it, and also want to improve my habits with my own personal and ...
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Reducing hash output length [duplicate]

I am using output of (keyed) hash function to make sure the input was not modified, I store it along with input. Now output of SHA-1 is 20 bytes. Say I want to reduce the output. And have it output 10 ...
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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?
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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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1answer
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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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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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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. * * ...
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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 ...
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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 ...
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492 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 ...
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Extract Password Hashes from Active Directory LDAP

Currently we are working on a monthly internal security test which among other should contain a verification of the real password strength the users choose. For this reason I want to extract the ...
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Is there a cryptographic function that generates a reconizable visual pattern?

I have to build a system that will ultimately print a pass allowing access to a building. The validation of this ticket will be done manually (it can also be automatic but that's not likely at this ...
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Testing a password for similarity to previous hashes

This question is a follow-up to a comment by Tobias Kienzler to an answer to "What is the purpose of the “Password minimum age” setting?". Consider a password policy that new passwords cannot be ...
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How can I identify this hash? [closed]

I'm trying to decrypt my router's root password, since I only have access to a simple admin account that doesn't have root privileges. Here is the passwd file: 0:F.bCrWv/Oxp6.:0:0:root:/home:/bin/sh ...
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What if I develop my own hash algorithm to create strong passwords from easy ones?

I came up with this idea but I cant figure out if it's good or bad, maybe you can help. My goal is: I want to create extremely strong passwords for my main accounts (gmail, skype and so on). I want to ...
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Hashing / How easy is it to infer the original input if the a slight variation of the input, the hash result and the hashing algorithms are known [duplicate]

Given that I have an initial input that is publicly known (e.g. "ABCDEFGHIJ") a slight variation of (1) (e.g. "BACDEFGHIJ") that is used as the input to a hashing algorithm (3) an modern one-way ...
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How do you overcome the problem of the salt being public and known by the attacker? [duplicate]

I believe that when adding a salt to the password you need to store the values so you can compute the hash again. But, what does happen if the attacker get the salt? How is it possible to add value ...