Questions tagged [passwords]

Passwords are secret keys which human beings can memorize.

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Crypto USB Devices - where is the PIN/Password stored?

I am currently looking at the security of cryto USB drives for storing x509 certificates. I have one in possession currently. It can be read/written to using the Microsoft Crypto APIs. Anytime one ...
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Ideal passphrase length: old diceware method (5 words) vs. your Bitcoin wallet.dat passphrase lenght (8 words) and doubling passwords?

I made a cool 5 word passphrase back then using the old Diceware method and use it as a master password. The question is as computing power increases will we need to add more and more words to our ...
superuser's user avatar
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A single password manager vs password generator/hash

I have been wondering about the options available for managing passwords. However, they all seem to fail if the master password is compromised (which isn't a big surprise). On one hand you have ...
Xeoncross's user avatar
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Exhausting the entropy of a hash function

In the case of password storage, consider the following: I have an idea that one can exhaust the entropy of input to the MD5 function by using a 128 bit random value as the password (indeed, any hash ...
Henning Klevjer's user avatar
1 vote
2 answers
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What can a master password also be called?

When having a company computer that is full disk encrypted, it is common that the boss have a master password / backdoor, so the data always can be decrypted. I have heard some call this for "scrow" ...
Sandra Schlichting's user avatar
0 votes
1 answer
316 views

Pseudo-random Number generation for Passwords

I am looking for a good pseudo-random number generation algorithm for passwords. My scenario is that I have to generate 5K pseudo-random bits from a user-supplied password (6 characters). What are ...
Mushahid's user avatar
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Seed a PRNG with random data and a password

I'd like to combine a random key file with a password to generate a secure seed for a CSPRNG. The key file is assumed to have very high entropy, but the password will be whatever the user provides. ...
brianmearns's user avatar
6 votes
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Is my password entropy calculation correct?

I have a password with a prescribed format: 111 + (2 Random lowercase letters) + (random digit) As you can see, it starts with a fixed value of ...
null's user avatar
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What happens to the entropy of a password when you hash it?

For example, if the entropy of a password is 30 bits, what is the entropy of the password when you hash it with MD5?
null's user avatar
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How is it possible to parallelize a hashing function to crack an iteratively hashed password?

Suppose I have an algorithm that relies on multiple iterations of a hash function like SHA1 to slow down an attacker trying to bruteforce a hash. ...
NXE's user avatar
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Which is more secure, using just bcrypt or SRP?

OK, here's the two different ways I was thinking about making the authentication for the login thing to store the passwords securely. The first is the following. Client hashes password bcrypt(...
133794m3r's user avatar
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What is the best-practice for encrypting small files?

I would like to know how to store a sensitive file; a credential of sorts. I want to password-protect it, obviously. It would be appropriate - in my application - to prompt the user for the password ...
Will's user avatar
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14 votes
2 answers
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Do I have to have a different salt for each password?

Should I use a different salt for each password? In my system, there are no user names, only passwords. When a user logins in, he types in one or more passwords and the server compares the results ...
Eyal's user avatar
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13 votes
3 answers
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Is there a way to make RC4 (ARCFOUR) secure, or is it completely broken?

I need a method to authenticate a process with another in order to establish interprocess communication between them, to prevent malicious processes from trying to hook onto the system. Currently I ...
Kevin Jin's user avatar
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10 votes
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How do I store encrypted files on a web server and decrypt them locally?

I want to store files (images) on a public webserver and let users see them if they know a password. The server shouldn't have the unecrypted files and the server can only serve files, not perform ...
Eyal's user avatar
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9 votes
1 answer
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Why does SRP-6a use k = H(N, g) instead of the k = 3 in SRP-6?

I've been reading up on the Secure Remote Pasword protocol (SRP). There are a couple different versions of the protocol (the original published version being designated SRP-3, with two subsequent ...
Robert I. Jr.'s user avatar
5 votes
2 answers
431 views

Do MD5's weaknesses affect Oplop?

Oplop is an algorithm that generates account-specific passwords from a master password and user-chosen nickname (typically username@domain). From the website: Concatenate the master password with the ...
Jordan's user avatar
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Is stretching hash several times basically the same as bcrypt?

As I understand it, the main advantage of bcrypt is stretching so it becomes slower to crack overtime. But, is using a "good enough" algorithm (e.g., SHA-2 family) then stretching until it's slow ...
user avatar
8 votes
3 answers
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Can I use a key-derivation-function as the hash function H in SRP?

In the Secure Remote Password Protocol, the verifier must be stored on the server. In the case of a server compromise, an attacker could obtain these verifiers. If nobody reused passwords, this ...
Jason's user avatar
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6 votes
2 answers
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Adaptive Hash Functions: How to tell how many iterations were used?

If an adaptive hash function like bcrypt or PBKDF2 is used in hashing passwords, the number of iterations used in the hashing process can be configured. For a penetration tester or a malicious hacker,...
Ayrx's user avatar
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Can a "pattern" in a series of passwords be detected from their hashes (and maybe a single raw password)?

Let's say I'm a lazy user of a system with annoyingly frequent password change policies. I may have a "good" password I used initially that is only used for this system but since I have to change it ...
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17 votes
2 answers
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Is bcrypt better than GnuPG's iterated+salted hashing method?

GnuPG has slow hash built-in in form of iterated+salted S2K. Does it have disadvantages in comparison with bcrypt or scrypt? Is GnuPG's slow hash method easily automated in GPUs?
Andrei Botalov's user avatar
25 votes
3 answers
931 views

What differentiates a password hash from a cryptographic hash besides speed?

I understand that password hashes like bcrypt have the principal property of taking a long time to run, but I'm wondering what if anything about password hashes make them superior to merely running a ...
Steven's user avatar
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3 votes
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Idea for user/pass hashing to prevent rainbow tables, would it work?

I'm very new to cryptography (and security in general, for that matter), but I had an idea that I'm sure is very flawed, but is worth asking. If a computer user, online account, etc, needs to verify a ...
tkbx's user avatar
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8 votes
5 answers
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How can I validate a hashed password if all I have is another hash?

The Scenario I have a client-side web application that bounces requests against a server-side API. For the sake of simplicity, every request must pass a username and password. This is similar to old ...
EAMann's user avatar
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2 answers
369 views

What is the advantage of an attacker over breaking a 4 digits PIN?

When a hardware system is protected by a 4 digits password, what is the advantage of the attacker into breaking that system? Isn't it $10*10*10*10=10^{4}$? If $\frac{1}{10^{4}}$ is the cost of such ...
curious's user avatar
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15 votes
3 answers
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Do I have to recompute all hashes if I change the work factor in bcrypt?

The well-known article about why we should use bcrypt for hashing passwords mentions the work factor - some parameter to the algorithm that determines how long one hashing should be in terms of number ...
sharptooth's user avatar
5 votes
1 answer
399 views

Why are there $ signs in my passwd file?

I am trying to get access to my eReader and I managed to get the passwd file. ...
nana's user avatar
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28 votes
3 answers
3k views

Is this password migration strategy secure?

I want to upgrade the security of some existing databases of users' authentication tokens strictly for the purpose of making sure that if the database is stolen, attackers will not be able to guess ...
Major Major's user avatar
5 votes
2 answers
1k views

How did LinkedIn "salt" all their passwords?

First, just to make sure I understand "salting" correctly: You randomly generate a string to append to the password before hashing it, so as to increase its length and make precomputed tables much ...
user541686's user avatar
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8 votes
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What's the reason for applying the hash twice when hashing with salt?

One of the typical approaches to computing a salted hash is this: hash(salt+hash(secret)) where hash is something like SHA-256 hash function - taking any size ...
sharptooth's user avatar
1 vote
2 answers
193 views

Idea for secure password hash-likes, is this feasible/usable/workable?

(Hand moved from stackoverflow.com,due to suggestion) Since breaking password hashes has become a new passtime for scriptkiddies, I thought of the problem and came up with a novel(?) idea. store ...
Markus Mikkolainen's user avatar
8 votes
2 answers
1k views

Hash decrypts key, key decrypts cipher... why?

I noticed recently that a couple of pieces of encryption software (TrueCrypt being one of them) don't directly use a hash of the password as the key for the block cipher. Instead, they generate a ...
Polynomial's user avatar
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5 votes
1 answer
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Is AES restricted to only 64 characters for the key/password?

I am wondering if AES only supports 64 character passwords? When using truecrypt, the maximum character limit on passwords is 64 characters; however, when using WinRAR, the limit is 128 characters. ...
rezx's user avatar
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3 votes
1 answer
101 views

Rapidly changing passwords?

Suppose you need to authenticate yourself to a program with the password - but the program's source code is public, the program doesn't have access to any private information and all your ...
Eric Yu's user avatar
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2 votes
0 answers
317 views

john the ripper, usages [closed]

As evident from the site of john the ripper, JTR example, john can be used for finding password form a unix machine passwd file. can JtR be used to crack password ...
Vineet Menon's user avatar
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5 votes
1 answer
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How is BCrypt secure when it uses a static dataset for blowfish hashing?

I'm planning on using this Javascript BCrypt implementation, but as you can see in the code, it uses a 4KB precalculated dataset for the P and ...
Robin Rodricks's user avatar
1 vote
1 answer
118 views

How to take SHA-1 safely for my particular case?

Let me ask about my toy passwords generator program X5 which I want to improve. X5 uses a secret key and a public key to generate a password.Where any public key is supposed to be known to hackers in ...
seven_swodniw's user avatar
4 votes
1 answer
2k views

How can I generate a one-time password?

Through my reading about the generation of one-time password (OTP) I found that there are many algorithms that generate OTP and they are either based on time such as TOTP or based on mathematical ...
MR.NASS's user avatar
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5 votes
1 answer
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Can I secure my key by XORing it with a hashed password?

I'd like to build a simple password-protected symmetric key system. The key-creation process in my system operates as follows: The system creates a 256-bit key purely at random. The user chooses a ...
apsillers's user avatar
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4 votes
1 answer
598 views

How can one share information using the 'host-proof' paradigm?

I am attempting to make a web-based secure password management and sharing utility, both as an academic exercise and to fully understand and feel safe about using it. I really like the idea of a "...
Travis's user avatar
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2 votes
2 answers
267 views

How can I store a combination of multiple pass phrases?

Let's assume we have 2 phrases, one is the real password from a user, and the other is generated from the real password and almost impossible to guess. You would need both to authenticate a user. What ...
Ronwe's user avatar
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6 votes
2 answers
5k views

Passwords with same SALT. What does this mean?

If the same SALT is used for many passwords on a Linux server, in what way is that a security risk? Does the mean, that a user (which can change his own password) can calculate other users passwords? ...
Sandra Schlichting's user avatar
148 votes
5 answers
128k views

What is a cryptographic "salt"?

I'm a beginner to cryptography and looking to understand in very simple terms what a cryptographic "salt" is, when I might need to use it, and why I should or should not use it. Can I get a ...
Bhavik Ambani's user avatar
-2 votes
1 answer
3k views

Store user passwords in database using Java Application

I want to store user's password details in Database. My project is in Java. I want to know the best way of storing passwords and other important information like user data.
Bhavik Ambani's user avatar
14 votes
2 answers
4k views

Use of salt to hash a password

In a few implementations of hashed passwords, I have seen that the length of the random salt is chosen to be, say, 10 or "some constant". Is there any specific reason why the salt is chosen to have a ...
hrishikeshp19's user avatar
5 votes
5 answers
444 views

In storing passwords in a database should I use a per-application salt in addition to a per-secret salt?

Assuming that the salts are sufficiently long (16 random chars) is there any advantage in using a per-application salt in addition to a per-secret salt when storing hashed passwords in a database? ...
Matt Parkins's user avatar
1 vote
1 answer
207 views

How is the password sent across for verification?

I am familiar with Challenge-Response Authentication scheme. However I would like to know actual message content sent between client and server for 1 way authentication, over an insecure channel. ...
orderof1's user avatar
  • 113
15 votes
5 answers
5k views

How can rainbow tables be used for a dictionary attack?

I'm putting together a password policy for my company. I very much want to avoid requiring complex passwords, and would much rather require length. The maximum length I can enforce is 14 characters. ...
Mitchell Kaplan's user avatar
1 vote
2 answers
4k views

How exactly would someone crack a private key passphrase? [closed]

Lets say for a PGP/GPG pair with a passphrase.
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