Passwords are secret keys which human beings can memorize.

learn more… | top users | synonyms (1)

0
votes
0answers
24 views

How to determine which key derivation function used for password?

Suppose an attacker collected a password hash file. After performing rainbow tables/dictionary attacks they choose brute force attacks. So they try guessing as many passwords as they can by running ...
3
votes
0answers
43 views

Soundness of GRC.com Haystack padding concept [migrated]

I was wondering how sound is the concept presented by the Gibson Research Corporation (see below if you do not want to follow the link) about simple passwords (= very easy to remember) with the ...
0
votes
0answers
37 views

Diceware word list for six dice

I really like Diceware, but it now needs six words to be safe. Instead of adding a word, I would think that increasing the size of the wordlist and adding an extra dice would be a better idea. I have ...
0
votes
0answers
37 views

Password generation/storage scheme

How bad is the following strategy for a password manager on a local machine? The user wants to sign up for somesite.com where he needs a password. The user has previously generated a secret key ...
8
votes
2answers
156 views

How Secure is a Pronounceable Password? In means of entropy

There are some strong studies which support the use of pronounceable passwords and multiple tools which provide generation of such passwords. According to this question the entropy of a password ...
0
votes
2answers
106 views

AES: Guess Password using the unencrypted text?

I am using the same password for some encrypted files currently (I know this is bad practice, though), and I wonder whether an attacker could decrypt if one decrypted file fell into his hands.
2
votes
0answers
64 views

Is it safe to derive a password from a signature provided by ssh-agent?

I'd like to use a password-based system on a remote host (accessed via SSH) without having to copy-and-paste the password and without storing it on disk. Using the system with some other form of ...
0
votes
2answers
98 views

Database row level encryption scheme

I am wanting to secure some highly sensitive data in a database. This would mean that the data needs to be encrypted and remain secure for 100 years if it were to fall into adversary hands. I also ...
0
votes
1answer
76 views

How to calculate the entropy of passwords? [duplicate]

Here is a cartoon about password entropy. http://xkcd.com/936/ I dont quite understand how the entropy is calculated in the cartoon assuming they are calculate correctly. But in general, I dont have ...
0
votes
1answer
175 views

Implementing a web app where the server cannot decrypt its own data?

I'm a cryptography novice, but I think that the world needs to move towards an "encrypt everything" mentality as much as possible. As a result, I've been thinking a lot about ways to build a web app ...
2
votes
1answer
164 views

Hashing passwords

The common way to store passwords in web applications is this form: $$hash(password||salt)$$ Does it make sense to store them in the following form instead:? ...
2
votes
1answer
153 views

Strong key generation using PBKDF

I know that PBKDF2 is very useful for generating strong keys. I'm trying to know is there any additional contribution of the given password to produce even stronger keys. Which key is more secure: ...
7
votes
3answers
829 views

Change Salt when Changing Password?

Assume a password storage scheme using a computationally-expensive hash algorithm and a CSPRNG salt. User ID, salt, and hash value are stored in a table; if the table is compromised, all three ...
2
votes
1answer
151 views

Why are some key stretching methods better than others?

I'm trying to understand why some key stretching methods are better than others. The wikipedia article presents 3 different key stretching methods: A collision prone simple key stretching ...
2
votes
1answer
84 views

PBKDF2-SHA256+SHA256 for password storage

I recently came across an interesting paper detailing the use of hardened session cookies. Each cookie includes a preimage of the password hash, and the preimage is hashed once more and compared to ...
3
votes
1answer
98 views

PBKDF2 Salt and Password Ordering

I am currently reading about PBKDF2, and understand that the salt is used only once, while the password is used multiple times in the computation of the final key (see this question). How would the ...
2
votes
2answers
76 views

Maximum password length in PBKDF2

Haven't found any clear cut answer in Google so its up to you guys: DK = PBKDF2(PRF, Password, Salt, c, dkLen) Here, what is the upper limit of password length? ...
4
votes
2answers
613 views

A patched SHA1 attempt for password verification

This is a classical scenario: For our web based authentication platform we have a username and a password field. User enters these values and presses Log In. The browser gathers the user data, ...
8
votes
4answers
308 views

Using hashes as passwords

I have thought of a system for generating passwords which works as follows: Take the following items: A password, such as williamwallace. A secret 1000 digit ...
4
votes
2answers
119 views

Allowing multiple password reset tokens, and a question on random number predictability

I have a few requirements for a password reset system, along with some questions at the end as to its security. Requirements The aim is to provide a password reset mechanism satisfying the following ...
3
votes
2answers
725 views

How long does it take to crack PBKDF2?

How much time will it take to crack PBKDF2 while using a 9 character password? I'm not specifying any specific system or platform. If a brute force attack is made using the best ever super computer ...
2
votes
2answers
152 views

What is the entropy per Diceware word if a random symbol is inserted into a random position in the word?

On the Diceware page is this little gem: For extra security without adding another word, insert one special character or digit chosen at random into your passphrase... Inserting a letter at ...
3
votes
1answer
95 views

Is there a practical upper limit for password rehashing?

When using PBKDF2, is there a practical upper limit to the iteration count above which we lose security? Note: If you answer “No”, that's fine. But if you answer: “There can't be an upper limit“, ...
5
votes
2answers
637 views

When only using one-way hashing, is it possible to tell the number of characters changed between the old and new password?

The other day when changing my password on a Solaris 10 system I was surprised that Solaris was able to detect that I hadn't changed enough characters between the new and current passwords. MINDIFF ...
2
votes
3answers
143 views

Do sites store login password with hash? If so, can people can use hash collision to log in?

I was researching about hash, and I thought, If sites store passwords with hash algorithms, then can't this happen: User A has the password 'hello' User B finds out the hash code of the password of ...
3
votes
2answers
202 views

Using PBKDF2 twice with different argument order

I'm pretty sure this is a really bad approach (in theory), but one of my clients is doing this and I was wondering… How bad it is to perform pbkdf-2 in this way (with 2000 iterations)? ...
3
votes
1answer
182 views

KDF followed by a Hash?

It is my understanding that a KDF adds entropy, whereas a hash loses information. I've read that KDF should be used to store passwords. I don't understand why we don't use a KDF and then a hash, so ...
2
votes
1answer
67 views

Is concatenated data hashed with scrypt vulunarable to a length extension attack?

scrypt takes a salt, and a password plus some cost paramters to generate a key. So say we define it as this: key = scrypt(password, salt, cost) I am interested ...
1
vote
1answer
95 views

Numeric combination of passwords

Pls I need explanation on How i can design a Cryptography that use multiple passwords or passphrase to open a safe(Lock). For example, if i need five people to unlock a secured device whereby all the ...
1
vote
0answers
121 views

Challenge–response authentication which can be done in head?

Say we have door where you have to say a password to pass. If theres someone standing nearby he would hear the password and could also use it. So therefore the doorman gives you a different number ...
1
vote
0answers
95 views

Trying to calculate the strength of a Bitcoin brain wallet created with a custom diceware password

I want to create a brain wallet using a custom diceware since I don't like the original one. Instead of 7776 words it has 46656 because I use 6 dice for each word instead of 5, and also it only has ...
2
votes
1answer
309 views

Strange Password Hashing

I know about PBKDF2, bcrypt, scrypt, etc. and while I'm not a crypt professional, I think I understand why are they better than just "hash(pass+salt)". But a colleague of mine surprised me with the ...
1
vote
0answers
95 views

Attacking hashed password by timing attack and other means

This question is inspired by this recent one, which raises a point that need to be made quantitative to be meaningfully discussed. I chose an unusual approach: a new question worded as homework that ...
5
votes
2answers
190 views

Can passwords be stored securely so that a similarity comparison can be made?

On the Pro Webmasters StackExchange site, someone asked a question about a webapp (in this case cPanel) that refused to allow a password change because it was too similar to a previous password. I ...
6
votes
2answers
276 views

Why do I need to add the original salt to each hash iteration of a password?

I understand it is important to hash passwords over multiple iterations to make things harder for an attacker. I have read numerous times that when processing these iterations, it is critical to hash ...
2
votes
2answers
627 views

Can a salt for a password hash be public?

For my understanding salts in password hashes are used to prevent the precomputation of $plaintext \to hashvalues$ (rainbow tables). I know from different threads, it is not necessary to keep the ...
3
votes
1answer
108 views

Calculate entropy of key derived from PBKF2 function

I am using PBKF2 to derive a encryption key from a password. suppose entropy of my password is y and my PBKF2 function has x number of iterations. So how to calculate the entropy of finale key derived ...
1
vote
1answer
91 views

Does it make sense to stretch non-keys?

I was thinking about stretching salt. Key-stretching is good against brute force guessing and assumes your system isn't compromised. Salting a one-way makes it so you have to compute * n for each ...
2
votes
1answer
121 views

password generation: random length or max length

In short: Is it cryptographically stronger to have a known length password of the maximum length allowed, or a random length password somewhere in the range of the longest length possible? Does the ...
0
votes
1answer
87 views

Biometric authentication [closed]

I see in some “Authentication schemes with biometric” papers that those authors wrote a phase as password and biometric update phase. My question is that why we may needs biometric update phase? Is ...
-1
votes
1answer
135 views

How do I cryptanalyze a password field?

In a PostgreSQL database, I can see the following fields in a table (for a specific record): User = administrator Password = "ceMv9Me6go" Now the following are true: The password length is not ...
6
votes
2answers
177 views

Why don't we use MACs to store passwords?

These days, the best practice for storing passwords is to use a scheme like scrypt or bcrypt. The goal of these schemes is to make dictionary attack inefficient for an attacker but it also slows down ...
1
vote
2answers
137 views

Splitting a password for dual roles [duplicate]

I would like to prompt users for a single passphrase to establish trust with separate, normally (but not always) complementary systems from one password input. I'm essentially looking for a box where ...
5
votes
1answer
231 views

What are the pros and cons of deterministic site-specific password generation from a master pass?

I've been reading up a bit on deterministic password generators. All the ones I can find basically do something like this: Pick a master username and a master passphrase. The username could be your ...
1
vote
2answers
103 views

Password as it relates to various encryption schemes

Suppose you have 2 drives you want to encrypt using different encryption algorithms, as an example: AES256 and Twofish. I am aware that using the same password for both could potentially weaken ...
2
votes
1answer
188 views

2 comparable hashes generated from one string

Assume a website where people log in with their password. The password is now stored in sql database as: md5(password + random_salt) We are adding the ...
3
votes
1answer
4k views

Decrypting the password from SHA-512 hash value

I am currently studying AES algorithm and writing a Code using Python. I am trying to add 'Salt' into the user input password, Here is what I am doing, ...
2
votes
2answers
250 views

Could completely public passphrase hashes ever be reliably secure?

This is a hypothetical question and I only have a basic understanding of Cryptography. If one were to follow the very best cryptographic practices for storing passphrases, could it ever be possible ...
2
votes
0answers
142 views

Integer factorization based password authentication

After looking at this security issue at DjangoProject, I started to think in a password-based authentication that places the burden of PBKDF2 (or whatever is the hashing function) on the client. So I ...
3
votes
2answers
263 views

bcrypt and pbkdf2 double hashing

If I want to protect myself from implementation of algorithm issues and inherent design flaws of algorithms in password hashing, what would be most secure way to combine two hashes? ...