Questions tagged [passwords]
Passwords are secret keys which human beings can memorize.
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Can a salt for a password hash be public?
From my understanding, salts in password hashes are used to prevent the precomputation of plaintext→hash values (rainbow tables).
I know from different threads that it is unnecessary to keep the salt ...
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Calculate entropy of key derived from PBKF2 function
I am using PBKF2 to derive a encryption key from a password. suppose entropy of my password is y and my PBKF2 function has x number of iterations. So how to calculate the entropy of finale key derived ...
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Does it make sense to stretch non-keys?
I was thinking about stretching salt.
Key-stretching is good against brute force guessing and assumes your system isn't compromised.
Salting a one-way makes it so you have to compute * n for each ...
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password generation: random length or max length
In short:
Is it cryptographically stronger to have a known length password of the maximum length allowed, or a random length password somewhere in the range of the longest length possible?
Does the ...
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Biometric authentication [closed]
I see in some “Authentication schemes with biometric” papers that those authors wrote a phase as password and biometric update phase.
My question is that why we may needs biometric update phase?
Is ...
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How do I cryptanalyze a password field?
In a PostgreSQL database, I can see the following fields in a table (for a specific record):
User = administrator
Password = "ceMv9Me6go"
Now the following are true:
The password length is not ...
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Why don't we use MACs to store passwords?
These days, the best practice for storing passwords is to use a scheme like scrypt or bcrypt. The goal of these schemes is to make dictionary attack inefficient for an attacker but it also slows down ...
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Splitting a password for dual roles [duplicate]
I would like to prompt users for a single passphrase to establish trust with separate, normally (but not always) complementary systems from one password input.
I'm essentially looking for a box where ...
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What are the pros and cons of deterministic site-specific password generation from a master pass?
I've been reading up a bit on deterministic password generators. All the ones I can find basically do something like this:
Pick a master username and a master passphrase. The username could be your ...
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Password as it relates to various encryption schemes
Suppose you have 2 drives you want to encrypt using different encryption algorithms, as an example: AES256 and Twofish.
I am aware that using the same password for both could potentially weaken ...
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2 comparable hashes generated from one string
Assume a website where people log in with their password.
The password is now stored in sql database as:
md5(password + random_salt)
We are adding the ...
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Decrypting the password from SHA-512 hash value
I am currently studying AES algorithm and writing a Code using Python.
I am trying to add 'Salt' into the user input password,
Here is what I am doing,
...
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Could completely public passphrase hashes ever be reliably secure?
This is a hypothetical question and I only have a basic understanding of Cryptography.
If one were to follow the very best cryptographic practices for storing passphrases, could it ever be possible ...
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Integer factorization based password authentication
After looking at this security issue at DjangoProject, I started to think in a password-based authentication that places the burden of PBKDF2 (or whatever is the hashing function) on the client. So I ...
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bcrypt and pbkdf2 double hashing
If I want to protect myself from implementation of algorithm issues and inherent design flaws of algorithms in password hashing, what would be most secure way to combine two hashes?
bcrypt(pbkdf2(pw))...
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salting with password hash to improve security?
Would something like the following improve security (against rainbow attacks, not brute force)? Assume that $P$ is a user-chosen password, and the objective is to obtain a hash $H$ for password ...
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Achieving 256-bit encryption strength with PBKDF2 - HMAC-SHA1
I am interested in the theoretical consideration of the bit strength of an encryption key and its precursor.
Assume a given environment as follows:
a. My encryption algorithm is AES-256
b. My key ...
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Secure Sketch Construction
I would like a user to choose a point on an image which is represented by (x,y). This is meant to be a security token. When a user uses this location to login they are unlikely to to choose the exact ...
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What's the most secure way to derive a key from a password repeatably?
I'm trying to write a cloud storage application where everything the user uploads is unreadable by the server, encrypted client-side before being sent.
Currently, the flow looks like this:
User ...
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Jumblar: Using map locations as passwords [closed]
I had the idea of converting map locations into passwords. Basically Jumblar (github.com/micheal-swiggs/jumblar) takes a hash of the user's location and stores this as a comment on the PGP network. ...
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using elliptic curve point multiplication as a key stretching method
My friend came up with the following idea: assuming we agreed on curve parameters, use the following algorithm for key stretching/derivation from user-entered password.
Pad the ascii representation ...
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Securely generating passwords based on a secret and a public identifier
I'm trying to create a good scheme for generating passwords in my systems management scripts. What I'd like to do is have a secret key (let's say hello123), which I ...
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How does the possible attack on passwords and salts mentioned in PKCS#5 v2.1 work?
From PKCS#5 v2.1, 4.1 Salt (page 6, emphasis by me), also in v2.0, RFC 2898:
In password-based encryption, the party encrypting a message can
gain assurance that these benefits are realized simply ...
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Is rainbow table attack applicable to any hash?
Typically when rainbow tables are discussed MD5 hash is used as an example. It's not quite clear whether this attack is specific just to MD5 or to a certain subset of hashes or to just any hash ...
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Password checking algorithm
I'm trying to reverse engineer a key exchange protocol which is based on the Diffie-Hellman key exchange scheme and faced with the following problem:
Let $g$ be the generator, $m$ the modulus.
Alice ...
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Trying to finalize my understanding about password storing
am sorry, an a beginner, so please forgive me if i make mistakes, so here is what I understood:
PBKDF2: uses HMAC, so, the message is the password, and the key that crypts the message is the salt? or ...
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How does Scrypt use Salsa?
Bcrypt uses Blowfish to encrypt a derived key from the passphrase, and Blowfish is a cryptographic algorithm, but here it is said that:
Note that
Salsa20/8 Core is not a cryptographic hash function ...
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Bcrypt VS Scrypt, Again?
I found this article on SO, but the answer was short, and the subject was closed,
What i don't understand, is:
Which one of the two limits memory usage to avoid custom Hardware to break the password?
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Which version(s) of SRP are in ISO/IEC 11770-4:2006?
I am on the impression that SRP emerges as the least uncommon and best analyzed protocol for authentication and key agreement based on a short password.
This states that SRP is part of IEC 11770-4, ...
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Encrypt a file once with 50 characters password or twice with 25 characters?
What better Encrypt the file once with 50 characters password or encrypt it twice each time with 25 characters password.
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Using an MD5 hash as a password
Suppose Alice is using a password prompt that only accepts up to 32 characters for any particular password.
Memorization of long strings of random characters is not one of Alice's strengths, so she ...
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Recommended way of adding a pepper/secret key to password before hashing?
There have been several questions regarding password hashing here and on Security.SE.
A "pepper" is sometimes mentioned – an application-specific secret key. The canonical answer on password hashing ...
user950
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Password verification
I'm looking for feedback on whether or not this is the proper way to approach password verification without transmitting the actual password. Are there any problems with this scheme.
We are working ...
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Using salted hash as password for easy memorization without reuse?
I had an idea earlier:
Secure passwords are a) long, and b) unpredictable. A hash is both of these. Would it be safe to reuse a key between sites, and include the site's name as a salt? For example:
<...
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Single-purpose symmetric encryption scheme for single files
I'm writing a simple password manager program that will encrypt/decrypt a single file (it's size will most likely stay under a few K). This is my initial file format design:
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It is reasonably safe to leave an AES encrypted RSA private key public?
The owner of the RSA key can't store the key, so they need to hand the key to an untrusted entity for storage. Before they hand it over they encrypt it using AES with a multi-word phrase they can ...
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Asymmetric password encryption - Viable? Which algorithm?
We have an application that requires cleartext passwords for user authentication because of the authentication mechanism in use (RADIUS/CHAP), which unfortunately we cannot change. Since we don't want ...
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Could a very long password theoretically eliminate the need for a slow hash?
Before I provide details, I want to clarify that I am not looking to implement this practically, but I'm only asking to get a better understanding.
The way I currently understand it, we use slow ...
user5182
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Sensible usecase for restricting special characters in passwords? [closed]
Please See Why Not Allow Special Characters In a Password on Security.
Several websites I've come across limit the allowed special characters for a password. My thought was, it should all be hashed ...
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Deriving HMAC key and cipher key from passphrase? [duplicate]
I'm encrypting a file with AES-256 in CBC mode. I needed to add an HMAC for authentication and validation of the file contents and passphrase, so I used a SHA-256 HMAC over chunks of my file ...
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Why does the SRP-6 calculation of B include a multiplier k = 3?
In SRP-6 $B$ is calculated as $B=kv+ g^b, k=3$. What is the purpose of $k$, and why was it fixed as $3$?
(In SRP-6a, this value $3$ is replaced by $k = H(N,g)$, but this question is about SRP-6.)
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Can the hash of one message be used to make it easier to find the hash of a very similar message?
Background:
I am trying to get an understanding of using a hash of a passphrase as a secret.
Example:
...
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Commutativity of keyed hashes
Definition
${H_1}^{K_1}(X)$ means data $X$ hashed by keyed hashing algorithm $H_1$ with key $K_1$.
Short question
Is $H_1^{K_1}(H_2^{K_2}(X))$ equal to $H_2^{K_2}(H_1^{K_1}(X))$?
Is $H_1^{K_1}(H_1^...
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How can encryption software accept password lengths which are not one of the AES key lengths?
AES comes with key sizes of 128, 192, and 256 bit.
But in Truecrypt or other crypto software we can use passwords of different length, even less than 128 bit or more than 256 bit.
How is this ...
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Hashing passwords with a salt - why use different salt for everyone?
Given a database where we have usernames and passwords, we want to secure users' passwords by hashing them. We should not use only username and passwords in this hash, as someone having data from ...
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Initialize a PRNG with a password
Let's assume that we have a secure PRNG. Is it "safe" to initialize it with password, or seed based on a password like SHA256(password)?
If yes, is it "safe" to generate an RSA or DSA key from it?
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How to generate a key using any $m$ passwords out of total $n$?
My application requires an AES-256 key K for some secure operation. In order to avoid saving this key in application, I have implemented following scheme:
There ...
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Encrypting or HMACing password digests
Assuming I'm using bcrypt to digest passwords, is any additional security gained by either encrypting or HMACing the resulting digests? By requiring a key to compare password hashes, I would expect ...
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estimate of time required to crack sha512crypt password with JtR + OpenCL
OK, I have a shadow file with a password that I know, it is 4 letters followed by two numbers. Using John The Ripper with OpenCL support, on a laptop with AMD Radeon Mobility graphics, how long would ...
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Where can I learn basic cryptography to know more about passwords and Bitcoin?
Basically my knowledge in passwords consist of setting up a Diceware master password back then, and I know hashes are not convertible back to the original password.
Some basic question I want to know ...
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