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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1answer
89 views

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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1answer
132 views

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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1answer
3k views

Pre-image attack on MD5 hash

I read somewhere MD5 is broken in terms of collision, but I am wondering if it is broken in terms of pre-image resistance? Given a hash of Md5, is it possible to find the original message of it? If ...
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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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3answers
152 views

Hashing items of different Bytes but same length would enable a timing attack?

I am following this paper which comes highly recommended as a secure Registration/Login system over TLS which uses client side computation for the Password Processing Function (PPF). What my main ...
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1answer
80 views

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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1answer
2k views

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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1answer
796 views

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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What is the recommended number of iterations for Argon2?

I've recompiled my operating system ("LionBSD" based on FreeBSD) to use Argon2i as the default password hashing algorithm in crypt/libcrypt. I'm wondering what the recommended number of iterations ...
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1answer
249 views

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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1answer
3k views

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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1answer
213 views

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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1answer
282 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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1answer
5k views

Traditional DES scheme in Unix crypt function

In a security context course, we need to reproduce the old DES hashing scheme in the crypt program, on an old unix system. I am actually reading the crypt page on wikipedia: The traditional ...
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1answer
207 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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0answers
546 views

Argon2 - memory setting - lower bound?

(I realise this is yet another Argon2 "how do I configure" question, but the existing questions I've found don't really help. If I've missed one, happy to have this closed). Deploying Argon2 (with ...
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1answer
463 views

Having trouble understanding reduction functions in rainbow tables

I'm continuing doing some personal research on rainbow tables, but forsome reason I cannot understand how to choose the correct reduction function. Wikipedia states that "Only when the attacker has ...
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2answers
851 views

VeraCrypt a weak point [closed]

Biggest flaw in VeraCrypt(or other Encryption programs) is Hash Algorithm. VeraCrypt hashes (SHA,Whirlpool,Streebog) it is the only point where can break an encrypted disk. Because break algorithm (...
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91 views

Secure hashing when the input comes from a small space

I have a problem that I'll simplify here. Let's say I want to store a table of {person, fav color}. Only, I don't want anyone to ever be able to look up a person't favorite color; the only thing ...
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1answer
103 views

Does having an SHA256 hash compromise PBKDF2 secrecy?

If I have a password pwd, and I hash it with SHA256 and send it to a server for authentication (server will apply ...
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1answer
98 views

How can a user-input password be used to generate a natural-like dictionary corpus?

I'm curious about the implications of cryptography and the generation of natural text (i.e using Markov chains), and I am wondering if there has been any cryptographic protocols that involved ...
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2answers
854 views

Should number of iterations of PBKDF2 stay secret?

Let's say I encrypt my passwords with PBKDF2 and store it somewhere. Now let's say it was stolen and the hacker, who stole it knows it was hashed with PBKDF2. Does a knowledge of number of iterations ...
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2answers
147 views

Why is it recommended to hash passwords with a secret salt?

NIST recommends doing an additional round of hashing using a secret salt: In addition, verifiers SHOULD perform an additional iteration of a key derivation function using a salt value that is ...
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3answers
780 views

Is it better to maximize memory usage or number of passes with Argon2i 1.3?

I wrote a small application that uses Argon2i for deriving symmetric keys for encryption of local files and secret Curve25519 keys. Argon2i v1.3 is susceptible to TMTO attacks if the number of passes ...
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5answers
938 views

How does a salt get chosen?

I feel like I am missing some information regarding salting. How does one choose the salt? If you reuse the same salt for all passwords, can it just be figured out and then used in conjunction with ...
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2answers
525 views

The logic of preferring PBKDF2 over iterative SHA2

I have studied PBKDF2 for the application of hashing passwords, and frankly I don't understand the justification for the complexity of PBKDF2 over iterative hashing with a cryptographic hash function. ...
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1answer
108 views

Ciphering the output of a password hash

In an article on password hashing security, Anthony Ferrara suggests using bcrypt to hash passwords and then using a "strong cipher (AES-128-CBC) with a key rotation policy". This seems like a good ...
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1answer
3k views

Is PBKDF2/RFC 2898 broken because SHA1 is broken?

I was attempting to re-implement the ASP.NET Identity password hash algorithm in PHP. It uses RFC 2898, which uses HMAC SHA1. SHA1 has been broken by google. Does this mean that RFC 2898 in general ...
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1answer
163 views

One-way hashing using singular matrices?

In matrix encoding, we convert our message into some numerical value and then create a matrix out of those numbers. The matrice encryption is based on the fact that a matrix multiplied by its inverse ...
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3answers
407 views

Authorities on password hashing best practice

I am trying to understand how best practices on password hashing come about. With password hashing, I mean specifically for the case of storing user passwords in a database in a hashed representation, ...
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2answers
410 views

Can't salt be easily removed from hashed password if access to the database was obtained?

After playing around with bcrypt I see that the database stores the salt and the hashed password is prepended with the salt. I read this article on how hashing should be properly used which also ...
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Did “The Catena Password-Scrambling Framework” make an error in the reduction of its pseudorandomness?

I was reviewing the most recent version of the Catena paper and they made some claims that I find questionable in their reduction of the pseudorandomness of the output of Catena (p. 32). First I will ...
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2answers
167 views

Zencash uses your passphrase to identify AND unlock a wallet - how is this secure?

When looking into Zencash I stumbled into myzenwallet.io (by the Zencash creators), which gives you the option to enter a passphrase to generate a wallet (seems normal), but then after creating your ...
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2answers
159 views

Security of password hash with known prefix and appendix

Assume I have a password that is exactly 32 characters long. I hash it the following way: Prepend 1524 bytes (known to an attacker) Append 3356 bytes (known to an attacker) Do the checksum It is ...
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1answer
2k views

How long will brute force of salted SHA-512 hash will take, if salt is known and possible characters in password are known?

Suppose I know that the password is composed of characters [A-Za-z0-9], length is unknown, but maybe less than 8. If I have information about the salt use to perform hashing, and also hashing ...
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2answers
161 views

Salt passwords with the username?

Salts should be unique so that an attacker can't brute force multiple passwords at once. However, since usernames are unique, wouldn't it be possible to use some representation of the username as a ...
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2answers
1k views

Why SHA-256 (or any other) is too fast for passwords but “slow” for collisions to be found?

Normally, the standard answers of why passwords shouldn't be stored using a groups of hash algorithms, including SHA-256 or higher, even if salted, are "because they are 'fast' hashes", "the attacker ...
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1answer
534 views

Salt length for a single password

So I've been reading about salt, and am confused about why the length is so critical. From my understanding salt is used for protection against pre-computed attacks. Say I have a single password ...
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1answer
141 views

Are there any known values for common hashes known to have no preimage

In a system which requires a user to have a password, as a quick workaround I wrote random junk as the bcrypt hash so that no one will be able to login to that user. However theoretically there ...
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1answer
547 views

Salt and pepper at both client and server sides?

Putting aside that it may sound paranoid. I know that many users tend to use the same password on many sites. Then, from an ethical point of view, I should not only be concerned about security breaks ...
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0answers
93 views

Fixed vs variable memory access pattern in password hashing

What are, quantitatively, the pros and cons of fixed versus variable memory access pattern in Password-Based Hashing, Entropy-Stretching Key Derivation functions, and Proof-of-Work applications? ...
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4answers
272 views

How many bits of entropy are leaked for every derived password from a master?

Given a master password that has a lot of entropy (similar to Bitcoin HD wallet seed words, 130 bits of entropy or more) how many bits of entropy are lost per leaked generated password? Let's take an ...
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4answers
568 views

salt usage for hashed password storage - design consideration

This is part of my academic assignment and hence to ensure no one feels i'm asking for the answer. I've given my opinion. Hashing is mathematical one way function that takes arbitrary length data ...
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2answers
80 views

Limiting password length to “prevent hash function splitting into multiple hashes”?

Given we are using well-known hashing functions for passwords, i.e. SHA256, SHA512, BCrypt or, PBKDF2. Our Information Assurance SMEs have advised that we truncate the input into these hashing ...
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2answers
169 views

How can a hash function be suitable for hashing passwords, but not for deriving enctyption keys, and vice versa?

Not being a specialist in this field, I am nevertheless constantly trying to keep up with which methods are being considered secure for storing passwords and for encrypting data. During my research ...
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3answers
534 views

What is the probability of a SHA-512 hash containing both digits (0-9) and alphabets (a-f) all the time?

Quite curious to know if ever a SHA-512 hash will contain only digits or only alphabets. Thanks in advance.
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184 views

PBKDF2 with longer than native output length - Will hashing the result help?

I've seen it mentioned more than once that PBKDF2 should not be used to create a longer key than the native output (such as 160 bits when used with HMACSHA1). Since an attacker could test only the ...
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1answer
1k views

Use sha3 for passwords hashing

Is use of sha3 justifiable? Is sha3 better than sha2 in (m)any aspects? P.S. I want to use hashing for passwords in a database
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136 views

How much less secure is an algorithm that gives feedback that the password is one character off?

If we had a stupid login procedure (SLP for short) like in this comic; it gives feedback on login, if the submitted password is one character off. Would a longer password be less secure? What would ...