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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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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Cryptographically secure hash function vulnerable to length extension attacks both to front and to back?

Is there any hash function where both $\text{hash}(m\|k)$ and $\text{hash}(k\|m)$ are vulnerable to length extension, but $\text{hash}(m)$ is itself secure?
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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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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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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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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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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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What password hash function for the next 50 years?

According to this report : http://www.ecrypt.eu.org/csa/documents/D5.4-FinalAlgKeySizeProt.pdf SHA2-512, SHA3-512, Whirlpool and Blake2b are hash functions that could be safe for the next 50 years. ...
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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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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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Why use argon2i or argon2d if argon2id exists?

So I am currently working on a GitHub project of mine and I want to implement Argon2. The problem is that I dont really know a lot about it. Internet research is not really helpful, because Argon2 is ...
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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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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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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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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 entropy much lower than entropy of encryption keys. Why is this acceptable?

When talking symmetric encryption, a 56 bit key is known to be so weak. If you use it for your encryption, you are considered a goner. When talking passwords however, the standard these days is ...
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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 ...
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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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How do I calculate a password space if the password only has eight alphabetic characters (not case sensitive)

I read this wiki article and saw this formula for random password's information entropy. Also the wiki article mention that the symbol count for non case sensitive is 36. Is there a way I can ...
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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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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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Recommended minimum entropy for online passwords in 2018

Assume a simple case, that an attacker knows the password creation scheme, and that we're not dealing with state actors, nor with sites which keep passwords in plain text. We're trying to defend ...
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How to configure Argon2d for commodity hardware?

You may already have heard it: KeePass v2.35 has support for a new database format (KDBX4) which allows for the use of Argon2 (more precisely: Argon2d) as the password-based key derivation function (...
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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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Can you use a hash as a password?

There are several methods of making a strong password, making it longer is one of them. now we also have hashing algorithms which have outputs of 512, so i wonder, would it be safe to basiclly use a ...
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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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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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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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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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Does the Balloon hashing paper deprecate Argon2?

Does the recent Balloon hashing paper and the included attack on Argon2 effectively negate the result of the Password Hashing Competition? On one hand it seems that only a constant-factor improvement ...
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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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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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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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Are coprocessors (Intel Phi) a threat for modern key stretching functions?

Modern key stretching functions (password-based key derivation functions, also used for password hashing) are memory-hard to mitigate parallel attacks, and as far as I know this is working well. Last ...
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Password derived hash to encrypt known plaintext as password check

The title sounds way too adventurous for what it actually is. I am currently building a system which features some encryption. There is already a system in place, which is built after that scheme if ...
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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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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 ...