All Questions
147 questions
0
votes
0
answers
36
views
Safety of password manager algorithm
I would like to ask about vulnerabilities of the following algorithm for a password manager.
It is structured as follows:
There is a master password UTF-8 10 characters long, not to be stored anywhere....
- 137
2
votes
1
answer
68
views
Can limited password/PIN length be compensated by a computationally intensive hashing function?
Say we have a very limited password space with only a 4 digit PIN, so only 10000 PIN possibilities.
Say also that the attacker has access to the stored form of the PIN.
Can breaking the PIN be made ...
- 123
2
votes
1
answer
50
views
Is hashing salt possible even with the password with salt appended to the end?
Should you hash the salt on its own ? Is that possible?
for example being password with salt appended at the end hash(pass || salt) and hash(salt) in a password file?
- 21
3
votes
1
answer
220
views
Is it possible to sign in to a website using two different passwords using an MD5 hash collision?
I wanna do an experiment. I wanna see if it's possible to sign in to an outdated website that still uses MD5 to store passwords (there are surprisingly still a lot) with two different passwords.
For ...
- 31
3
votes
1
answer
101
views
Can using an unknown, non uniform random salt increase difficulty for password attacks?
I remember reading a previous stack exchange post (unfortunately was unable to find the link, if someone knows the link that would be great!) about a method to make password checking time for the ...
- 33
1
vote
2
answers
480
views
Is sha3 a one-way funtion
If i store sensitive stuff (e.g passwords, salted passwords, Internet protacel adresss(so i know its not tamperd with), private keys(the keys are using a portion of the key on multiple disks in ...
- 23
5
votes
4
answers
927
views
Sending password to server vs. sending SHA
This is an existing website with approx. 100K accounts, and passwords are hashed using bcrypt with a high number of rounds.
The current design that I'm questioning is that we're sending the username ...
- 185
4
votes
2
answers
2k
views
Password hashing and salting with SHA-256 on $2^{64}$ password space
If a password is randomly chosen from a space of $2^{64}$ passwords and is stored as an SHA-256-bit hash and a 128-bit salt, how many hashes does an attacker need to perform to recover the password in ...
- 161
1
vote
0
answers
103
views
How many hashes to recover a salted password? [closed]
If a password p is selected from a space of 2^64 passwords, and the server stores this as a hash, h = SHA-256(p||s) where s is a random 128-bit salt. How many maximum hashes would an attacker need to ...
- 161
1
vote
1
answer
446
views
KEY using AES-128, If P is less than 128 bits, padded with 0 and create 128 bits, any problem if average pw length is 6
For communication between the client and the website, use password (P) as the key using AES-128. If P is less than 128 bits, it is padded with 0 to create a 128 bits key. is there any problem with ...
- 11
1
vote
2
answers
232
views
Debug bcrypt iterations with a static salt [closed]
I want to debug bcrypt rounds with a static salt using this python lib
...
- 491
0
votes
1
answer
55
views
How easy is it to identifiy the key when knowing a certain number of different AES-256/Fixed Nonce encrypted long-integers
Given some intervals of long integers (64 Bits). I need to generate alphanumeric strings which:
should be used like passwords(known only by few individuals)
must always be the same for the same ...
- 111
0
votes
0
answers
32
views
User to be able to log in without stating the user's password scheme possible?
In my database, I have a PBKDF2 hash + salt for every user. My objective is for the user to be able to log in without stating the user's password (in case somebody is logging the network traffic ...
- 99
1
vote
1
answer
2k
views
Can you break PBKDF2 if you know the hash of the password?
I know that PBKDF2 hashes the password a number of times, the result being a key. Can an attacker find the key if they don't know the password, but know the value of the hash of the password?
user278629
2
votes
2
answers
333
views
Hashing Passwords and Hash Functions
I'm a complete noob. I was reading up on hash functions. So if a bank has its user password's run through a hash function, it'll produce a unique hash for every password right? Thus, even if hackers ...
- 21
1
vote
1
answer
590
views
Is this authentication protocol secure against both eavesdropping and server database disclosure?
Consider the following protocol from the book "Network Security: Private Communication in a Public World" by Kaufman et al.
Alice knows a password. Bob, a server that will authenticate ...
- 113
3
votes
2
answers
606
views
Impersonation attack on Lamport's one time password
So here I am, googling my brain on the possibilities of impersonation attempts by a MITM attacker on Lamport's one-time password scheme.
Here's my scenario:
Say we have a client and server setup. ...
- 153
2
votes
1
answer
839
views
Which passphrase length is good so it's hard to break bitcoin's PBKDF2 key?
According to https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki#From_mnemonic_to_seed
To create a binary seed from the mnemonic, we use the PBKDF2 function
with a mnemonic sentence (in ...
4
votes
1
answer
2k
views
Is password hashing post-quantum secure?
Current computers cannot break reasonably strong hashed passwords, for example 14 CSPRNG-generated alphanumeric characters ($\approx$80 bits of entropy).
Grover's algorithm applies to hash functions ...
- 1,538
7
votes
3
answers
3k
views
Password hash contained '\x00' in middle, resulting in ValueError from bcrypt.hashpw
I have some code that accepts a password in string format, and hash it with SHA3-512 before passing it to bcrypt for hashing. However, by some coincidence, I found a test case that produces a hash ...
- 173
1
vote
2
answers
268
views
Would hashing a password twice prevent naive attacks?
A common way of using MD5 or any other hashing algorithms to store passwords is to hash the password with a salt $$\text{hash}(\text{password} \mathbin\| \text{salt}).$$ This way, if an attacker wants ...
- 121
2
votes
1
answer
391
views
Is tagging the hash of a password along with ciphertext secure?
Suppose I have a password, in which I use Argon2ID with 1GB memory to derive an encryption key. Then, I encrypt my data using XChaCha20 using that encryption key. The problem with ChaCha is that any ...
- 469
1
vote
0
answers
97
views
Should I use 2x the number of CPU / core for Argon2id parallelism?
I've read that I should use 2x the number of CPU available from some documentation while others suggest using between 1 and the number of CPU.
I realize there is no hard answer here but I'm curious ...
- 111
0
votes
0
answers
80
views
What can be deduced/extracted from this local hash extracted from Windows Machine?
I'm new to cryptography. I've been experimenting with getting Windows hashes to see whether it's possible to reverse engineer. The following hash is what I got from my test laptop. What can you ...
-1
votes
1
answer
708
views
Is storing salts encrypted a good idea?
I've read that storing password hashes in a database, you can store the salt in plaintext alongside the actual hash with no detriment to security. I was thinking that one could derive a key from the ...
- 119
1
vote
1
answer
189
views
Combining algorithms for password storage?
Is it more secure to combine algorithms for password hashing, for example, Scrypt, Bcrypt, SHA-3, etc.? If an attacker wants to use dedicated hardware, he would need one for each algorithm. However, I ...
- 363
1
vote
0
answers
4k
views
Relation between Zoom id,password and join URL [closed]
We all are using zoom application for joining/hosting meetings in this corona virus period. As we create a meeting, a new id, password and a url is generated. Some real examples follow-
Id: ...
- 111
0
votes
2
answers
493
views
For uniterated SHA-256 of salted password, should the password precede the salt?
This is a follow-up to this question (thanks to answers from @fgrieu and @kelalaka
) about the format of a salt when hashing a salted password.
I realize this is pretty much academic, as the proposed ...
- 115
1
vote
2
answers
861
views
What format should a salt be when it is concatenated with the password?
Assume that, in the available environment, it is not possible to use modern password hashing functions (bcrypt, scrypt, Argon2, PBKDF2, etc.), so it is necessary to roll my own stand-in, until they ...
- 115
2
votes
1
answer
538
views
Does pepper *require* an HMAC?
Assume you are already given a properly-salted, password hash $X$ from some slow PBKDF (e.g., like Argon2id).
Now, you want to apply some large (~256-bit) secret "pepper" $S$ to it before storing it ...
- 343
1
vote
0
answers
109
views
Signal Key Stretching Regarding Their Blog Post
I just read this blog post (Signal - Technology Preview for secure value recovery) by Signal and something is not quite clear to me. In section "Stretching beyond a KDF" they generate a ...
- 111
2
votes
1
answer
112
views
Choosing between hash functions instead of providing a salt for a password hash
I am working on some programs that require the users to store their passwords in my databases.
However, due to the fact that I am not sure whether salt should be stored in databases due to my ...
- 159
3
votes
1
answer
525
views
How slow is the hash used for Mac FileVault encryption?
Certain password strength estimators (for instance, zxcvbn) give estimates that vary with the speed of the hash and the assumed resources of the attacker. I am curious what hash is used by the MacOS ...
- 85
0
votes
1
answer
94
views
Two party protocol using only hash function
I have been told by my professor to compare two passwords as we do it in Yao's two-party protocol but without using any crypto functions. We are only allowed to use a hash function. The passwords are ...
4
votes
2
answers
4k
views
What's the algorithm behind MySQL's sha256_password hashing scheme?
MySQL's old mysql_native_password hashing scheme was the equivalent of this in PHP:
sha1(sha1('password', true));
That's a ...
- 143
0
votes
1
answer
164
views
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 ...
- 3
2
votes
5
answers
413
views
Why are password database breaches bad if cryptographic hashes can't be reversed?
If companies such as Facebook store our passwords as hashes, when they are leaked how can this be a threat to the users? I thought of it because nowadays we do not have computational power to break ...
0
votes
2
answers
463
views
Where is the password hash calculated, locally on or the server?
My computer security professor uses the following notation, where S denotes a server and A denoted Alice. Alice wants to authenticate herself to the server. The hash function is a hash chain where $h^...
- 90
3
votes
3
answers
299
views
Two salts, One password
If I have two different MD5 password hashes with two different salts (the salts are known), is there any way to cryptographically deduce if the two passwords match? Other than brute force password ...
- 31
0
votes
1
answer
339
views
Padding vs Hashing Encryption Key
I am making a program for personal use that will not contain super-sensitive information. I am using this to explore cryptography. Would it be acceptable to use a password to generate a key for AES, ...
1
vote
2
answers
2k
views
Hashing login and password?
For a login the user credentials are typically some form of "username" and a matching "password".
The password is (hopefully) stored as a hash in the database.
But what about the username?
Is the ...
- 6,511
0
votes
2
answers
299
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 ...
- 119
1
vote
1
answer
933
views
Safety of having many passwords hashed with the same salt?
I'm working on a web application where passwords must be hashed on the client before it can be send to the server. This is because the user's raw password is used for cryptography purposes and can't ...
- 121
2
votes
2
answers
576
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 ...
- 2,065
2
votes
2
answers
1k
views
HMACSHA1 vs HMACSHA2 (for PBKDF2)
I need to choose an HMAC function for PBKDF2.
I'm using .net so I don't have the option to use SHA3. At first glance, and according to this answer by Thomas Pornin it seems like SHA512 would be best....
- 2,065
1
vote
1
answer
1k
views
What is best practise for salting and multiple-hashing of passwords?
I have been presented with some custom PHP code for salting passwords and applying multiple rounds of hashing.
It looks reasonable, but I fear home-grown crypto.
Is there an existing password ...
- 968
1
vote
1
answer
8k
views
How do you get the original salt after it's been hashed to the user's password in the database?
I'm researching how to do salt and hashing. I'll be using SHA256. Here is what I found:
To Store a Password
Generate a long random salt using a CSPRNG.
Prepend the salt to the password ...
- 19
1
vote
2
answers
822
views
Comparing different hashes to confirm they came from the same string
Is there any safe hashing algorithm that returns a different hash each time (like bcrypt) but has the possibility to compare 2 different hashes and determine that they were hashed from the same ...
- 11
1
vote
2
answers
268
views
Can multiple hashing weaken the password?
Problem. I want a longer key out of password than my hashing function provide.
Idea. I want to hash password multiple times rotating chars one position each time and use composite key.
Question. ...
- 67
0
votes
1
answer
4k
views
extract password hashed in scrypt using hash and salt [closed]
I have the hashed password and its salt. It is encrypted using SCRYPT by firebase.
How can I extract the plain text password from these two?
Or alternatively, how can I re-encrypt or convert them ...
- 101