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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Aren't password managers still incredibly risky?

I understand the utility in having one application remember a bunch of long, randomized passwords, but all you'd need is one well-placed phishing scam or a keylogger and they get all the keys to the ...
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381 views

“Please Enter Nth Character” without HSM

This question has been asked a few times, but always in the format "How does examplewebsite.com implement their 'please enter xth yth and zth characters of your password' function?" And the ...
11
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What did Blackberry do wrong?

The NIST defines a vulnerability in RIM Blackberry encryption discovered last October. Apparently, Blackberry's flavour of PBKDF2 was weak. They say: The offline backup mechanism in Research In ...
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What is a good practical (and sane) way to manage all your passwords for online sites?

I am just a mere mortal that wants to have a somewhat secure way of managing all my passwords. This is something that I have been putting off, but since LinkedIn decided to give away one of my ...
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Do salts have to be random, or just unique and unknown?

First of all, my motive is to avoid storing the salt in the database as plain text. As far as this question is concerned, the salt is not stored in the database. After discussion in comments and in ...
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Is there any advantage of bcrypt over multiple iterations of SHA-x/MD5?

I know that a good password hashing algorithm should be slow. MD5, SHA256, etc. are fast. So I've been adding multiple iterations of SHA-256 hashing to my web apps (around 50000). Getting the hash of ...
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3answers
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Cryptographic Security of Dynamically Generated, Non-Random Salts

So when it comes to security, when I have an idea that seems good, but no one else seems to be doing, I try to assume that I'm overlooking something obvious or otherwise significant. This is one such ...
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Is it okay to widely share the RSA key fingerprint for a host?

When you ssh into a remote box for the first time or if the remote host's key fingerprint has changed (from what's stored in your known_hosts file) you get a warning and you are shown the fingerprint ...
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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 ...
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How secure is the SRP that Blizzard uses to protect passwords?

Blizzard very recently announced that their network was compromised, but they assure users in their statement that the password information that the attackers had access to was saved in a secure way: ...
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Is there a length beyond which increasing password length provides no additional security?

Assuming that the password is stored hashed and salted, and that it is a string of random characters, is there a point where adding to password length doesn't add security? Since the hash will have a ...
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How can I make sure password hashing is secure on computers while not being prohibitively slow on mobile devices?

I'm new to cryptography and its implementations. I'm designing an Android app where an user enters a password to retrieve some encrypted data. After some research on possible solutions I ended up with ...
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Any risk in using the same salt for several hashes on a user?

Right now I'm storing a salt and password_hash on the users table (pretty standard stuff). The need arose to get a secure hash of another field for a user. Is there any risk in reusing the same salt ...
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How often do two users use the same password

If no two users use the same password, then in theory salting the password hash is not needed. How often, in practice, do two users have the same password?
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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 ...
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6answers
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Should I hash a password if it is randomly generated

The best practice is we should hash a user password using algorithms such as bcrpyt to protect the user, however, given the following conditions, is hashing in the backend still matters? the ...
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Client side password hashing

Edit: Updated to put more emphasis on the goal - peace of mind for the user, and not beefing up the security. After reading through a few discussions here about client side hashing of passwords, I'm ...
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619 views

Does it make sense to choose a longer password than the output of a hash?

Let's take MD5 for example: It outputs a 128-bit hash. Does it make sense (in theory) to choose an input (password) which is itself longer than 128-bit? Does it increase the probability of a ...
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4answers
521 views

How can I be secure with a global salt?

If I understood the basic of password hashing and storing, what we need are: a "strong" salt a "real" random salt a unique salt per password a password hashing function with a high CPU cost We ...
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480 views

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 ...
9
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758 views

BCrypt's 72-character limit and using it as a general digest algorithm

Goal: have token/cookie-based authentication that doesn't require keeping sessions on the server TL;DR: What, if any, is the accepted mechanism to work around the 72-character limitation of BCrypt? ...
9
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2answers
441 views

PINsentry PRNG and Bank Cards

My bank provides me with a device similar to this: The device is essentially a PRNG, presumably based on the date/time of it's internal clock, synchronized with the bank servers. To generate a pin ...
9
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1answer
184 views

Securing a prediction about a future event

I want to make a prediction about a future event, but only reveal that prediction after the event occurs lest knowledge of my prediction affect the outcome. For example, suppose Alice predicts that ...
9
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250 views

Proving running code on a website is unchanged

Can it be proved to the user that the running code behind a website with security related code is the same as published? I'm currently looking at a few new project ideas and one involves secure ...
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3answers
901 views

HMAC Based Request Signing - Storing the Salt

I'm working on a (non high security) project that currently isn't live but might go live at some point. We have a REST API (implemented using Restlet and Neo4j) running on a server and an Android ...
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2answers
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How does Google not care about “spaces” in Application-specific passwords?

I have recently setup "2-step verification" for my Google account. One of the features is the ability to create "Application-specific passwords " for devices that do not support the 2 step process. ...
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Estimating the size of a rainbow table

What are rainbow tables and how are they used? Gives a very precise answer about what rainbow tables are and how they are used. I had always confused hash-tables and rainbow tables. My question is ...
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Safety of publishing last 4 credit card digits in age of fast computing?

How safe is it to make public the last four digits of a credit card? Credit card numbers have a specific format. Digits tell you what type of institution issued the card, what bank issued the card, ...
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What is the problem with chain hashing?

Let's say that my password is a single character: "a". Couldn't I chain hash it 1000 (or more) times and make it nearly invulnerable to rainbow table attacks and brute force? Why isn't this ...
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What's the advantage of using PBKDF2 vs SHA256 to generate an AES encryption key from a passphrase?

I'm looking at two comprable pieces of software which need to encrypt data on disk using a passphrase. One uses PBKDF2 to generate the encryption key from a passphrase, while the other uses two rounds ...
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4answers
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Is using HMAC to transmit a password OK?

I'm writing a small webapp and I don't want to transmit login passwords as cleartext. As I don't have SSL available I've written a one-time challenge system which sends a random string with the login ...
8
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4answers
455 views

How to evaluate the strength of a hashing algorithm?

At work the hashing algorithm we use for passwords appears to be bespoke. Obviously that's a pretty bad idea, but the management don't seem bothered. The algorithm always produces 20 character long ...
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moving from MD5 to SHA-512

This question is more of a security policy than a technical security question. Many years ago I developed an asp.net site, implemented Forms Authentication, and stored the user passwords as MD5 ...
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At what point does adding more iterations to PBKDF2 provide no extra security?

If my true passphrase is used only to generate a hash which is used as the cipher's actual key, doesn't that mean it's possible to try and brute force the cipher itself? I know it would take an ...
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Using MD5 for malware ids: collision attack risks?

It has been known since 2004 that the MD5 hash is vulnerable to collision attacks (update - not "preimage" attacks - my mistake....). Yet it still seems that people are using it to identify malware. ...
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Choosing a session ID algorithm for a client-server relationship

I am developing an application which has a client-server relationship, and I am having trouble deciding on the algorithm by which the session identifier is determined. My goal is to restrict ...
8
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808 views

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 ...
8
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Are different hash algorithms ever used together?

I was wondering if different hashes (e.g. md5(sha1($data)) ) are ever used together for data security and if there was any reason for it (either positive or negative answer).
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Is this code snippet good enough for password hash and salt

After a few days reading up about salting and hashing passwords, I found an actual bit of code that tells how to do it. This is what I found: $blowfish_salt = ...
8
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4answers
688 views

Does hashing a PRNG make it cryptographically secure?

Would hashing the result of a regular random number generator produce a cryptographically secure PRNG? For example, would sha1(rand()) effectively be a secure PRNG? Assuming it doesn't, how would ...
8
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1answer
329 views

General purpose slow/unique hash routine for dup checking of private data, without storing the data itself?

I am wondering if there is a percentage of uniqueness known to be lost with every repeat of various hash routines, like MD5, SHA1, and how that might compare with other algorithms. If theoretically I ...
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Is a HMAC-ed password is more secure than a bcrypt-ed or scrypt-ed password?

Given an option , which one should I choose , a HMAC for storing a password securely or a bcrypt or scrypt library?
8
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Is there more to password hashing?

You have a plain text password and salt. The plain text password is assumed to be securely random and only known by the user and the salt is no secret and not necessarily unique but stored alongside ...
8
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1answer
690 views

Is there repetition in the Solaris 11 hash routine? Can I add some?

Solaris 11 now uses SHA-256, so we can have longer than 8 character passwords now, by default. That is nice. I'll just make it clear that this password is never used as a line of defence. Only a ...
8
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1answer
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Cheap to validate yet expensive to compute hashing algorithm

I am looking for a hashing algorithm somewhat like bcrypt, except that I would like validation to be extremely cheap. As an anti-spam measure I would like to require my clients spend say, half a ...
8
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1answer
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“Official statement” on php.net : CRYPT_BLOWFISH is strongest hash algorithm. Why?

First: I asked this question on stackoverflow and was kindly asked to post this here again. See the original question here. According to the [early] doc pages of the new PHP 5.5 password ...
8
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2answers
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Stretching a hash, many iterations versus longer input string

I have been reading up on various password hashing schemes, for example the SHA-based Crypt proposed by Ulrich Drepper and used in some Linux versions. A recurring theme here is to 'strengthen' or ...
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How can we factor Moore's law into password cracking estimates?

How would we go about factoring Moore's law into exceedingly long password cracking estimates? Let's say we've got a 12 character password containing mixed-case alpha characters and numbers, i.e. ...
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Authenticated Encryption vs. contained and encrypted checksum/hash?

So I read through http://en.wikipedia.org/wiki/Authenticated_encryption and http://www.cryptopp.com/wiki/Authenticated_Encryption and I don't seem to be following the concept. From the simple ...
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How difficult is it to modify an ISO image and still have the old md5 check sum?

If I want to download the ubuntu11.04.iso then: UBUNTUMIRRORSRV -> ISP -> ISP -> etc. -> MYPC I just want to ask that how difficult is to spoof the original MD5 sum (e.g.: the md5sum would be ...