Questions tagged [passwords]
Passwords are secret keys which human beings can memorize.
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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 ...
user64440
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Can "OPAQUE-over-TLS" authentication be optimized?
So while discussing the issues of password-hashing off-loading in our chat I noticed that it's easy to extend OPAQUE (CFRG draft) to essentially be a better standard password based authentication when ...
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Possible combinations of 8 digits, 6 upper case letters, 2 distinct numbers
Assume I want to find out how many combinations there are for a 8 digit word with 6 uppercase letters and 2 distinct numbers, e.g. A7BC9DEF, 1A0CRDEF, ... how many ...
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Mutual keys protection/wrapping
Is there a known risk in having two keys wrapping each other?
Let's say, an adversary has access to both AESkey1(key2) and AESkey2(key1).
Does it make it much easier for him to recover the keys?
Bjorst
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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^...
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64 bits password = 13 characters?
If we use upper and lower case letters, and 10 digits, we get
approximately 6 bits per character. Then, strings of 13 characters
should work.
I saw above explanation in the material, but I cannot ...
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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 SHA512 ...
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Password re-use by another person or on another service
How does having the same password in different services make it less secure? How does having the same password as someone else make it less secure? Very basic question that I've always wondered about; ...
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How many passwords are possible in this scenario?
A password string consists of one or more of the 26 characters A..Z and can be of any length from $1$ to $8$ characters. How many password are possible in this scenario?
As my calculation, it should ...
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Decrypting SHA-512
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 SHA-512 hashed. My doubt is that when ...
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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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Calculating entropy within xkcd 936: Password Strength
When I calculate entropy for the xkcd Password Strength (comic 936) I don't get nearly the amount of entropy stated in the comic.
So why doesn't the the first password "Tr0ub4dor&3" have an ...
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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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Does it make sense to have long SSH Key with shorter Passphrase?
If we encrypt our data with a longer SSH key which is protected by a shorter passphrase (with a decent entropy), then the limiting factor is entropy of the passphrase. So why do we use a longer key at ...
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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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Hardware, Handheld Password Manager
I am currently working on a hardware project that will utilize the native USB and keyboard emulation capabilities of the Teensy device. Essentially, the user will store an encrypted password database ...
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Is using a smart card and password two-factor authentication?
I use a smart card - as read only device - for user identity as well as a password:
The smart card (holds the user ID) is something I have;
The password is something I know.
Is this still two-factor ...
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Avoid decrypting every password in a password manager
The Setup
I'm making a password manager for fun. It stores a random encryption key, encrypted with a key derived from the master password, and then it stores the data, which is a list of (site, ...
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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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Client-side password stretching - danger of the salt being public?
In case of using client-side password stretching (plus a single hash on the server) - the server would need to send the salt before authentication, of course.
Though the salt is not considered a real ...
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Are PBKDF2 derived keys related if only the number of iterations is changed?
I'd like to encrypt my disk with a password.
To generate a nice key from a password, I used PBKDF2, which applies a hash function $k$ times to a cleartext and outputs the final result.
When I modify ...
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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 ...
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Quantum security risk to present encryption
Quantum computers will seal the fate of conventional encryption techniques. Of these, the hardest hit will be the RSA algorithm used by 99 percent of all applications the encryption standard for any ...
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Is a singular LUKS volume with different passwords that unlock different filesystems possible?
So it's hard to make sense out of the title. Let me elaborate:
In LUKS, you can have multiple passwords that unlock the same volume (due to their "unified key setup" where they have a single master ...
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Password protection in ARJ: 3 characters of password are retrievable
On this site there is information that one can know first 3 characters (bytes) of the password without brute force. I know that ARJ in older versions has very simple encryption, i.e. XOR with ...
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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, ...
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Bounding security of password authentication given entropy
An adversary Craig tries to log-in as Alice on a system that will only accept the right password, leaks (only) if an attempt succeeds, and allows many attempts.
Alice's password choice is modeled as ...
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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 ...
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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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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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aWallet Password Manager
After reading a lot of articles on ramping up the security of my web accounts, I started using aWallet Password Manager for Android to backup my passwords. I like ...
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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 ...
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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 ...
user56826
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Expanding truly random key into printable password for successive hashing
The STUN network protocol defines its client authorization in the terms of message-integrity check employing the following scheme [RFC5389, section 10.2]:
$$
\DeclareMathOperator{\HMAC}{HMAC}
\...
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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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SCRAM Iteration Count Attack
I'm not sure if this questions belongs here or in the Information Security Stack Exchange, but here goes...
With SCRAM (RFC5802), is there anything that prevents an attacker masquerading as the server ...
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Benefit of capitalization when using Diceware passphrases?
If I use a Diceware generated passphrase of any given length, will capitalizing the first word (or any word for that matter) effectively double the number of combinations that would have to be tried ...
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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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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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Diffie-Hellman based password challenge response scheme
A very commonly used (examples: HTTP digest auth/CHAP/Kerberos) authentication scheme is something that looks like:
Setup.
Client and server both know a password $p$.
Authentication.
Server sends ...
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For WinRar, how long should a password be to make up for a lack of complexity?
Assuming that the best alternative to complexity is length, how long do you recommend a password or phrase to be when using WinRar?
Note that I'm aware that it's not always that simple, but I would ...
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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
user55326
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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....
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Why is password recovery so slow for Whirlpool hash, when compared with others?
I'm just curious about why brute force takes so much longer on the Whirlpool hash than it does on the others, as you will see below:
...
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Does this PBKDF2-SHA1 payload hint at a cryptographic security issue?
Blockchain first 16 encrypted bytes, IV, and iter_count – all encoded in Base64:
Yms6xqrzCfFsQadVZ5gQonMtnQAAAAAAAAAAAAAAAAAAAAAQJwAA69tYNg==
Does it looks like “...
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Password hash that can be upgraded without plaintext password
Most password hashes have a cost parameter that indicates how long the algorithm should take. Is there an algorithm where you can increase that cost for a particular hash, without access to the ...
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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 ...
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Is it safe to store both the AES-related data and the PBKDF2-related data (except passwords) in one file?
Assume an "encrypted data package" file format which includes the following data
PBKDF2
algorithm
salt
rounds
keylen
AES
algorithm & mode
IV
ciphertext
where the PBKDF2 salt and AES IV are ...
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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 ...
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Salt for non-stored passwords
I have read a lot about the concept of adding a salt to a password and understand that it protects against various attacks, especially the use of rainbow tables. But this kind of attack is based on ...
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