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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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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688 views
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 ...
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8answers
580 views
Is the following authentication scheme secure?
I was trying to design an authentication system that would make it much harder to guess a password via brute force, and reduce the risk to a user if the hashed password was stolen through a snooping ...
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5answers
876 views
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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4answers
2k views
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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4answers
997 views
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 ...
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4answers
1k views
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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6answers
570 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
...
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2answers
218 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 ...
7
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3answers
322 views
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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2answers
394 views
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 ...
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208 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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1answer
438 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 ...
7
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1answer
657 views
Would it make sense to use Bcrypt and PBKDF2 together?
I've read various opinions about whether Bcrypt or PDBKF2 is a better key derivation hashing method. The answer seems to depend on a lot of complicated factors that are not easy to analyze. Would ...
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1answer
346 views
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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2answers
805 views
With PBKDF2, what is an optimal Hash size in bytes? What about the size of the salt?
When creating a hash with PBKDF2, it allows the developer to choose the size of the hash. Is longer always better? Also, what about the size of the random salt? Should that be the same size as the ...
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2answers
416 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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137 views
“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 ...
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2answers
566 views
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. ...
6
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6answers
753 views
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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3answers
48 views
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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2answers
493 views
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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3answers
233 views
Increase the security of an already stored password hash
Right now we're using 1024 byte PBKDF2 with 256 byte user-specific salt and variable iterations. However, I would much prefer to be able to, perhaps once every year or two, to be able to flat out ...
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5answers
302 views
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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248 views
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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3answers
313 views
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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3answers
482 views
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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3answers
320 views
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 ...
6
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1answer
827 views
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 ...
6
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2answers
487 views
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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3answers
605 views
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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2answers
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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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2answers
630 views
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 ...
6
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2answers
359 views
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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1answer
105 views
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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2answers
389 views
Production ready bcrypt implementation for .NET
Which, if any, .NET / C# bcrypt implementations are considered suitable for production environments?
I have seen CryptSharp and BCrypt.Net mentioned in answers to other questions but without any ...
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4answers
482 views
Is sha-1 hash always the same?
Is it possible to ensure that a string is hashed always the same way no matter which language you use to do it (Java, vb.net... ) and no matter what operative system you are?
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8answers
717 views
Does truncating the cryptographic hash make it impossible to crack?
I store password hashes in their full value for example, $h = sha256('foo') outputs 64 characters: 2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae
I store that directly in the ...
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4answers
911 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 ...
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4answers
711 views
Using password hash as session ID?
For a rich client web app, on the server I need to verify that each call comes from a legally logged in user. Obviously user ID is not enough, because that's easy to guess.
I have an idea I am ...
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3answers
247 views
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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4answers
3k views
Brute force vs other methods of recovering passwords from shadow file
Do you know any good approach for de-hashing/actually bruteforcing hashed passwords in the shadow file?
On various operating systems, any good solutions/methods/programs.
Or is it better to upload ...
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3answers
487 views
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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3answers
649 views
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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2answers
1k views
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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4answers
262 views
How to upgrade the hashing method of a live database without compromising security?
I'm working on an Intranet project that is accessible from the outside. The password are stored in a Sql Server database in the normal Hash and salt method. The problem lies in the hashing algorithm.
...
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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?
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3answers
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With ASIC bitcoin miners, should SHA256 be considered insecure for password hashing?
I'm sure everyone here has seen the rise and further rise of bitcoin. The process used for mining bitcoin is basically "let's brute force an SHA256 hash that is less than this amount"
That being ...
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3answers
432 views
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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1answer
119 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 ...
