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 bad practice to ask only for individual characters of a password? [duplicate]

Some financial websites that I use use passwords in a peculiar way. Instead of asking me the whole password string, they only ask me to enter e.g. "3rd, 5th and 8th character of your password", i.e. a ...
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Why secure encrypted data consistency by strong hashing?

Consider the SSH protocol: the SSH packet is like [data, SHA1(data)]. The packet is entirely encrypted by a block cipher. The question is, why do we need a strong hash to protect the packet ...
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Not hashing email registration confirmation link

I sent emails out that contains an email registration confirmation link: http://example.com?create=email%3Djay%40gmail.com%26confirm_key%3D53e321f97c145 I do not hash the link above. Before I sent ...
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SHA, RSA and the relation between them

SHA is the hashing mechanism. However, RSA is the encryption algorithm. So does RSA algorithm use SHA hashing mechanism to generate hashing keys which in turn is used to encrypt the message?? ...
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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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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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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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How secure is HTTPS with weak ciphersuites?

Today I came across the website https://mtgox.com/, which claimed to be secure because of the Verisign certificate. I checked the certificate out of curiosity (it's the first thing they claim, let's ...
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Hashing length for storing password

Does larger hash size improve the security? Is it overkill to use 512 bit hash? If I stored only 256 bits of the PBKDF2-SHA512 derived key, is it less, equal or more safe than 256 bits of ...
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Is my session-less authentication system secure?

So, I've created an authentication system. Poured over it for any kind of security flaws and tested the crap out of it. I think it's fairly secure, but there is one "different" by-design aspect of it ...
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PHP crypt() trims the salt as it would be too long

I am using Blowfish with PHP crypt() for password hashing but I noticed something weird. Quoting PHP documentation: CRYPT_BLOWFISH - Blowfish hashing with a salt as follows: "$2a$", "$2x$" or ...
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Does bcrypt on top of md5 reduce its security?

A GitHub project I recently checked has a flawed security as they're using an unsalted md5() to hash the passwords. I opened a bug and they acknowledged it. However, the transition from md5() to ...
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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 ...
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Is Using MD5 Sufficient Reason to Reject This Payment Processor?

I'm evaluating a credit card processor[1], and I noticed they are using MD5 as part of a salted hash algorithm to protect a secret key. Since I know MD5 is generally considered broken, this feels like ...
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Secure way to shorten a hash

If I want to save a hash of a certain number of bits, but my hashing algorithm gives me more bits than I need, then what is the safest way to shorten it? Should I: Just remove the first or last ...
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Salt placement prior to one-way hash

In one-way hashing its common to prepend or append the salt to the secret and then hash it: (salt + secret) or (secret + salt). I was thinking of this metaphor as salt falling on a plate of food. It ...
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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 ...
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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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How to crack password hashed using SSHA?

Is it possible to crack a password hashed using SSHA if I know the salt? How can I do it?
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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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Bcrypt as a key derivation function?

I read a lot of entries at stack exchange about bcrypt and why it is supposed to be better than PBKDF2 in terms of password storage. I'm asking now if bcrypt is better than PBKDF2 in terms of key ...
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Does Outlook store plain-text passwords?

A long time ago when Microsoft changed my e-Mail from Hotmail to Outlook the password-interface said that I should only put in the first 16 chars of my password. But my password was longer before. So ...
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New to security, is php password_hash() good enough?

This is the first time I've had to handle personnel information and I want to make sure I have a good amount of security. I will be storing users' emails and passwords for their accounts on a MySQL ...
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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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Encrypting short identifiers?

I am developing a webapp that does not reveal record count, because it hides the primary key. I am looking for a better way to do this. My favorite idea is to encrypt the ID itself with a block ...
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Keeping user data private in a cloud environment like Google App Engine

I am writing an open-source Java application for Google App Engine (GAE). The application will let users create content that is intended to be private. I want to provide reasonable assurances that ...
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Does password-hashing “busy-work” need to be cryptographically secure

All modern password hashing schemes are deliberately designed to include a huge amount of "busy-work", to limit the speed with which an attacker would be able to conduct password hashing attempts. ...
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Any problems with scrypt yet?

In the question Do any security experts recommend bcrypt for password storage? Thomas Pornin recommends the hashing function scrypt but saying it is "too new to be recommended on a general basis". ...
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Techniques to make a login page safe without using SSL

I am developing a web page where people can write and comment things (no personal informations required) and I need to put a log in form so users can see all their actions on my web page. My idea is ...
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What is the best way of securing a website logon without SSL or preshared keys?

Today I sniffed some unencrypted wlan traffic during class and I found quite a few passwords by a simple search for "pass" and "user" in wireshark. Turns out about half the sites we use for school ...
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How weak is MD5 as a password hashing function ?

A professor told us today, that MD5 is weak. I understand his chain of thought but pointed out, that IMHO MD5 is a good way to go if you would use a long (even really long) dynamic salts and static ...
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How can Microsoft validate a shorter password on Microsoft accounts (MSDN)?

I recently ran across this when logging into MSDN. (I saw this screen after typing my initial credentials.) I have a 20+ digit password, however there's apparently a new requirement for Microsoft ...
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Are online hash calculators dangerous?

I was about to use an online MD5 checksum calculator when I realized that my result could be added to a database. This is significant because the string I was going to type in was my bank password. ...
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Is it better to hash n*x times in sha1 or n times in sha512 on the client side?

I already know I"m going to hash the user's password n times in either sha512 or n*x in sha1 before it is sent to the server. Once at the server, I'm going to use bcrypt set to use ~1/100th of a ...
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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 ...
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Patient Hashes for Compression and Security

Are there any front-running approaches to using server-generated hashes to encapsulate patient condition in a concise manner while maximizing security? For example, a system to represent current med ...
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Does checking the fingerprint of a self signed certificate improve security?

I am currently developing a component for an application that does TCP communication with a device inside a local area network. I use TLS to provide data encryption, integration and authorisation. ...
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Would secure storing of past used/generated passwords be a good idea?

Let's assume an organisation that generates ~100 Passwords a week; these Passwords are 32-Characters long and randomly generated. The consultants that need passwords generated use a Password-generator ...
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What algorithms are best be cracked by GPU?

What algorithms are best being attacked by a GPU powered password cracker? For example, I heard that md5crypt that is being used in unix shadow file, is not the best choice for GPU cracking because it ...
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Is it safe to store hashes of possibly non-existing passwords in a less safe way?

I would like to implement a lockout mechanism that not only protects against same username and many passwords attacks, but many usernames and same password attacks too. To implement this I figured I ...
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What is “c/s” in context of hash cracking?

I was reading hashcat's About page, and the stats are listed in terms of c/s....is that "Cracks per seconds"....the 'c' part seems wrong, I'm just guessing. What is 'c'?
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Bank account number and account holder in check exposed?

I'm not sure if this is standard practice in all banking institutions but almost all banks where I've received checks the account number of the issuer is exposed (some even the account name). Isn't ...
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Global check of input/output of known hash functions

Is there a website, application, or script that will allow you to give an input/output for a hash function, run these against known functions, and return any matches? Here's one attempt to list the ...
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How do I use Skein's Stream Cipher?

I understand the NIST hash function competition candidate Skein comes with a built-in block cipher, Threefish, that is turned into a stream cipher by using Unique Block Iteration chaining (is that ...
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Calculating password hashes in the browser?

I just finally got into Keybase and was surprised to see this in the sign-up page: Shouldn't password stretching and hashing be done on the serverside, as we normally don't trust a client?
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Is it safe to use PBKDF2 for hashing?

I would like to get a few opinions on whether it would be safe or not to use PBKDF2 to generate a hash of a password. For my purposes I'd like to assume that the hash itself will be posted on the ...
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chosen plaintext attacks against MD5 and SHA1

According to http://tools.ietf.org/html/rfc2617#section-4.9, having the server chose a nonce but not having the client chose a nonce opens up Digest Access authentication to chosen plaintext attacks. ...
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Is there a hash algorithm that can identify similar files or strings?

Is there a hash algorithm that will help you identify similar files or strings? For example, the hash for ABC and XBC would be similar rather than radically different as is usually the case. I know of ...
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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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NTLMv2 resistance to bruteforcing

I have a question regarding NTLMv2 resistance to password bruteforcing. I know that some modern graphic processors (like Radeon 6990) are able to calculate billions hashes per second and crack NTLM ...