Passwords are secret keys which human beings can memorize.

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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" ...
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1answer
199 views

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. ...
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1answer
310 views

password entropy calculation

I have the following password with a prescribed format: it starts with a fixed value of 111, followed by 2 random lower case letters and then lastly a random digit: "111""2 Random lowercase ...
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1answer
601 views

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?
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3answers
284 views

Stretching passwords 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 ...
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2answers
545 views

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 ...
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2answers
2k views

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 ...
8
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1answer
3k views

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 ...
7
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1answer
400 views

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 ...
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2answers
256 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 ...
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2answers
186 views

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 ...
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3answers
2k views

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 ...
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2answers
416 views

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 ...
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2answers
2k 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 ...
7
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2answers
567 views

Is bcrypt better than GnupPG's iterated+salted hashing method?

GnuPG has slow hash built-in in form of iterated+salted S2K. Does it have disadvantages in comparance with bcrypt or scrypt? Is GnuPG's slow hash method easily automated in GPUs?
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3answers
358 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 ...
4
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1answer
324 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 ...
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2answers
177 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 ...
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1answer
345 views

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 ...
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2answers
141 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 ...
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2answers
668 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 ...
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1answer
2k views

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. ...
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1answer
73 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 ...
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0answers
181 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 ...
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1answer
460 views

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 ...
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1answer
73 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 ...
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2answers
182 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 ...
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1answer
408 views

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 ...
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2answers
604 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? ...
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5answers
274 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? ...
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1answer
134 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. ...
8
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6answers
789 views

How can I improve a password generation scheme based on a shared secret and URL?

I currently use the following method to generate a different password on every website I have to login: password = SHA1 ( mainPassword . domainName . number ) ...
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2answers
2k 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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2answers
277 views

If Bob steals Alice's private key, how exactly would he read her encrypted documents?

So Bob grabs Alice's secret key when she isn't looking and her encrypted files, doesn't he need to know her passphrase to read her files? What I am reading is that no he does not need it but as far ...
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4answers
996 views

Webapp password storage: Salting a hash vs multiple hashes?

For security's sake, of course it's blasphemous to store passwords in plain-text; using a hash function and then doing a re-hash and comparison is considered much better. But, if bad guys steal your ...
4
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1answer
161 views

Is a changing public truecrypt container secure?

I have a Truecrypt container which I want to synchronise between computers (i.e. different people, that I want to share the data with). If I used Dropbox for synchronisation and someone downloaded ...
6
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3answers
2k views

SHA1 usage for passwords, alternatives and advantages?

My application can authenticate via openid and oauth (facebook, twitter, etc) and also with its own authentication system. I previously switched hashing from MD5 to SHA1 and during migration I had to ...
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3answers
1k views

Dictionary attack on pass-phrases on common algorithms

I don't yet perfectly understand the difference between brute-force and dictionary attack since this differentiates one attacking the key and another attacking password: apparently attacking passwords ...
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2answers
845 views

How should I store passwords that need to be available in plain text?

Suppose I need to store login information for a third-party website for a few users, how would I go about doing it? Since I am logging into a third party website, I need the password in plain-text, ...
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1answer
599 views

iSeries (AS/400) Database File: password encryption

I am helping with a project in which an old software system on an iSeries is having a brand new .NET UI applied to it. It's going well... except... In order to allow users to login and maintain ...