Questions tagged [password-hashing]

Irreversibly converting user-selected passwords into authentication tokens that can be safely stored e.g. in a user database. Typically done with a salted password-based key derivation function (PBKDF), ideally with a memory-hard mixing stage to thwart brute-force attacks using parallel hardware.

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46 views

Is there a point in storing hash or plaintext in the last column of Rainbow Tables

As I read up on rainbow tables, I found that most sources suggest storing a plaintext - the result of Rk(hk) - in the last column, while others just store the hash hk, basically stopping one step ...
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exfiltrating salts with timing attacks?

It seems to me that it's theoretically possible to exfiltrate a salt against a hashing algorithm that isn't constant time using specially crafted inputs. Are there any examples of this being done in ...
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How would quantum computers affect password based encryption?

At first glance: Assuming that the output of the password hashing function is large enough, quantum computers should have no effect on password encryption as on symmetric cryptography in general. Is ...
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Password to password mapping

DISCLAIMER: I understand the question might be a bit amateurish due to my limited knowledge of cryptography but, please, bear with me for a minute. QUESTION: Suppose a user Alice generates a pass ...
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Does character encoding change entropy?

This is a question I've been wondering for a while. Technically these two strings have the same entropy I believe: ...
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Add a pepper to a hash: as a string or a buffer, and should I calculate a hash of a peppered plain text?

I'm using a bcryptjs to generate a computationally slow hash function for storing passwords: ...
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Understanding Encryption length calculation and rounds

I am trying to learn about password encryption by creating a simple password hashing algorithm, although many online articles did warn "Do not create your own algorithm". I discovered that most of ...
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Can you find the salt if you have the original password in plaintext and the hashed version?

Suppose that I have a password in plaintext. I also have the hashed version of the password. Say it uses MD5. Is it possible to find out what the salt is given the above information? I'm guessing not?
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How secure are public hashed passwords (with a salt)?

I'm working on a blockchain-based distributed application which stores Client information. I'm thinking of alternate ways to authenticate ...
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How is PBKDF2 so much better than normal Hashing or even using HMAC

I do not know how the Key Length extension attack works. So if we leave that aside for once, and say just about usual brute-force attack on the hash, I don't really know how is PBKDF2 so much better ...
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What is used as a KEY and MESSAGE when using HMAC within a PBKDF2? [duplicate]

I was studying WPA2 and it's security when I came across this problem. I know that WPA2 uses PBKDF2 to generate a Pairwise Master Key. It does something like this; ...
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When to use Argon2i vs Argon2d vs Argon2id?

I've read the manual, and multiple articles / StackExchange posts about this topic, but still can't decide which implementation of Argon2 is best for my use case. I want to securely encrypt passwords ...
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Should i hash or encrpt the data first? Why? [duplicate]

Lets say alice is trying to send data to bob , should alice first hash the data and then encrpt or vice versa
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Authenticating without sending password to the server, and store data encrypted with password derived key on server

I am trying to think of a scheme that would allow a user to authenticate to a server, whithout sending the password to the server, and to also derive a symetric key on the client (that also never gets ...
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Password Hashing Security Using Scrypt & Argon2

I am developing an app where the following cryptographic system will be in place: Elliptic Curve key exchange (curve: secp521r1) Double Scrypt the shared secret with different salts Pass this result ...
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Keyed Hashing and verification

Is there any standard algorithm where I can create a hash H(x,k) where x being the data and k being the private key. And verify on other end with H(x,l) where l being the public key? How it can be ...
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Choice of delta-neighbors in Balloon Hash algorithm

Reference Document: https://eprint.iacr.org/2016/027.pdf According to appendix D section 4 definition 27 each vertex in V has predecessors sampled independently and uniformly at random from the ...
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pwd-hash like algorithm which can be computed on paper

"Common password problem" is well known problem, when user uses one password for many resources (web sites, logins to computers, etc...) For example, if one web site loses it' database, which contains ...
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Key Derivation Functions vs. Password Hashing Schemes

Key derivation functions, such as HKDF (standardized in RFC 5869), are meant to stretch some initial keying material having enough entropy, like a Diffie-Hellman shared value, into one or more strong ...
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Does it make any difference when salting database passwords with Random vs SecureRandom?

I want to salt database passwords and then compute the hash but I wonder if I should use Random or SecureRandom? From an attacker perspective would it be easy to break if Random is used or ...
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Password hashing alogirthm simple enough to implement myself?

I'm doing a password manager for a school project and I need to hash the master password for verification but I also need to write the hashing algorithm myself. However, most the algorithms I've come ...
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Why is PerfectForwardSecrecy considered OK, when it has same defects as salt-less password hashing?

PFS suites suffer from the same defects as any other salt-less password hashing scheme. Why is everyone promoting Perfect Forward Secrecy (PFS) ciphersuites so fiercely? Namely, when the group/hash ...
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Use a hash-function twice

I'm creating a small messenger and I wanted to know if it makes sense to store user passwords double-hashed in our backend-database. I wanted the user the register in an app, which should save a hash ...
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How to get a speedup linear in the number of iterations on unsalted iterated password hashing?

In their 2015 paper "More Rounds, Less Security?" Guo, Jean, Mouha and Nikolić claim in section 5.4 that one can recover a password $P$ given hashes of $D$ different passwords generated from $H^k(P)$ ...
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What are the major advantages of SPHF for PAKE?

I am working on Password Authenticated Key Exchange (PAKE). I noted some PAKE schemes were built upon the smooth projective hash function (SPHF). I am confused why SPHF can be used to design PAKE? I ...
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Does encrypting a result of AES block cipher provide more security?

I would like to know if encrypting a result of AES256 block cipher provides more security. Concretely, I am developing a system in which a client sends to a server a ciphertext encrypted with AES256. ...
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Why derive keys from a master key instead of generating random keys?

I noticed AWS KMS generates encryption keys based off of a master key, using a key derivation function (HKDF). What's the practical advantage of deriving keys based on a master key? Isn't it simpler ...
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Brute forcing/hacking Secure passphrases - difficulty for random strings vs real words

I was wondering about this topic of brute forcing passwords,or ANY other way to deriving them - and asking myself whats more secure (relatively): A Password which includes A) 30 digits length- a ...
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How difficult is it to guess a salt based on a hash and known plain text?

I have the following use case: Alice owns the domain alice.com and Bob owns bob.com. I want to users to create a hash for ...
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Storing passwords in a publicly available database

I have a public database where users need to store configuration files. The file can contain passwords. Everyone can read config files but only the server can read passwords in them. In the browser, ...
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Deriving a key from a pseudo-random string

I would like to know if deriving a key from a pseudo-random string with a single iteration is secure. Concretely, I am designing a system where a secret key is derived in the client side, and then ...
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hash algorithm for user accounts passwords in macOS 10.12, 10.13, 10.14

I study this article: How to Hack a Mac Password Without Changing It and get interested in what hash algorithm is used for hashing user accounts passwords in macOS 10.12+? My hypothesis is that it ...
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Best practices for saving encrypted user data without a database

We are setting up a web application which requires users to submit sensitive data. Since entering all the required data may take a long amount of time, we want to give them the option to save their ...
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Argon2 for both password storage and key derivation

Is using Argon2 for both password storage and key derivation secure? I'm planning on using different salt values, of course. The basic concept is something like this: Alice has some secret data ($...
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Is It Safe to Reuse the Same Salt in Bcrypt Password Hash (Specifically for Chaining Hashes)

As explained in my previous question, I want to develop a scheme which would be able to increase the password hash strength without the user password. According to Thomas Pornin it should be safe to ...
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How many bits should I request from PBKDF2 to create a strong password?

I'm building a tool which generates passwords by hashing a service name with a master key. PBKDF2 was primarily chosen due to availability in the Web Crypto API. What would be a secure value for the ...
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Are there any known security issues when doing the following chaining of BCrypt Hashes: 'bcryt(bcrypt(user-pw, work-factor1), work-factor2)'

I am currently developing a protocol which would be able to "upgrade" the strength of a bcrypt password hashes without the knowledge of the user-password so a system may upgrade it without user ...
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Upgrading key derivation by adding a XOR with a known value

In general keys for password based key derivation are derived from a password hash such as the old PBKDF2 function or Argon2, possibly followed by another derivation function to derive data and ...
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Would using a hash of the site name salted with a master password be a secure password for all sites?

I am considering creating an application that is able to work out a unique password for a site by hashing the url while using a secure master password as a salt (or technically pepper since it will ...
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Difference between SSHA512 and SHA512

I am using SSHA512 to encrypt email user's passwords. Manually doing this works using doveadm from dovecot. But I can't seem to implement this in my mail client. I can, however, use SHA512. Is ...
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How do hashes really ensure uniqueness?

This might seem an impractical and unnecessary conversation, but I feel it's something I need to clarify. Especially, as I just got my first developer job in a blockchain startup. So hashes are said ...
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GUIDs as a salt

Quote: Most of these answers are a bit misguided and demonstrate a confusion between salts and cryptographic keys. The purpose of including salts is to modify the function used to hash each user's ...
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Reasonable Password Entropy given a certain Set of argon2 Parameters

I followed the recommendation of choosing threads, memory consumption and the number of iterations (in that order) on my machine. But now I wonder which passwords (by means of entropy) are actually ...
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Decrypting SHA512

I was recently solving a CTF problem and it involved a shadow and passwd file. I got to know the username easily but I am unable to find the password since it is SHA512 hashed. My doubt is that when I ...
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How to prove that a rainbow table is complete?

Passwords that are hashed but not salted can be cracked using the rainbow table. I went through this and this which explains the logic behind rainbow table very well. But I am missing something about ...
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Is it possible to determine the number of characters used for a password used to encrypt a file with AES 128?

I lost a password for an ethereum wallet at the end of 2016. Computer immediately shutdown and password was not recoverable. I know there are many potential avenues for narrowing my search for what ...
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203 views

Hashing user password without database to store salt

I am building an Android app that will run purely locally on the user's device, no servers. It has a database that I want to encrypt with the user's password, which requires a 64 byte key. I've ...
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280 views

Why does PHP crypt give this unexpected result [closed]

So I have this PHP code,it is meant to encrypt a users password... Three problems/questions: My 'salt' CHANGES ITS NAME I get the same result Is this actually how the result is meant to be? PHP CODE ...
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Secure password-authenticated key exchange that allows for passwords to be stored as hashes, but does not make the hashes password-equivalent

Are there any secure password-authenticated key exchange that allows for passwords to be stored as hashes, but does not make the hashes password-equivalent? This would be useful for many ...
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finding encoding based collision

For example, If I enter as a sample "hello world" in English, then the hashing protocol by encoding the text to binary strings makes the hash. What if I find a word in other languages like Hindi or ...