Passwords are secret keys which human beings can memorize.

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How secure is Shamir's Secret Sharing for password sharing when attacker has t-1 shares?

I am designing protocol to share a random generated n long password between k parties using Shamir's Secret Sharing. I know that share alone does not reveal much information about the original ...
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1answer
175 views

Backdoorable hash function in password database

I want to use a (preferably established) hash function that is backdoorable in a password database. I want to do so because I need password escrow (being able to get the cleartext back. I want to ...
4
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2answers
201 views

Public key crypto instead of hashing passwords in a database

Suppose I want to keep a client's password database secure (not in plaintext), while still having access to the plaintext password. Now I generates a public/private keypair. Then I send the public ...
2
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1answer
153 views

Is it true that 7zip doesn't use any salt with its KDF?

This issue claims that 7zip does not use any salt with its key derivation function: https://github.com/magnumripper/JohnTheRipper/issues/1679 If that's true, wouldn't that mean you can crack multiple ...
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3answers
909 views

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 ...
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1answer
168 views

Cracking passwords with more than 10 characters in a few hours?

I came across this article from 2 years ago: http://www.dailymail.co.uk/sciencetech/article-2331984/Think-strong-password-Hackers-crack-16-character-passwords-hour.html They're describing how a team ...
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1answer
94 views

gpg --gen-random quality level: is higher “better”?

The GNU Privacy Guard manual pages have this to say about using the gpg --gen-random 0|1|2 count command: Emit count random bytes of the given quality level 0, ...
2
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1answer
205 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:? $$hash_1(hash_2(...hash_n(password||salt))...
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1answer
72 views

Is it safe to generate ECDSA keys from the hash of the previous, over and over again?

I have memorized a very long and secure passphrase, that when hashed with sha256, I can use the result as an ECDSA private key, and use it as a brain-address for Bitcoin. Now I need more bitcoin ...
2
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1answer
74 views

Can the salting function complexity improve the hash robustness?

I'm quite novice in security, and all examples I saw seem to salt the password by concatenating it, or by applying a simple binary OR or XOR. So the hash is based on "salt + password", "salt | ...
2
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1answer
110 views

Memory hard password based key derivation functions?

How are memory hard functions designed for the purpose of password based key derivation? To protect against a brute force attack from a parallel machine. What design could work well with Skein? The ...
2
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2answers
655 views

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(...
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2answers
379 views

How secure is a pronounceable password in terms 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 ...
1
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3answers
105 views

Is this client-side password hash scheme secure?

I want to build an app that uses client-side encryption for storing encrypted data on the server. A user-specific master key would be used, so to easily share it between devices a encrypted version of ...
3
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1answer
64 views

Public SRP verifiers or public hash chain “public keys” when secret is low entropy password

I want to set up the following: An untrusted server should host user sessions and authenticate users without knowing their passwords or being capable of creating a fake user session in the user's ...
2
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1answer
98 views

How does the small n attack work?

I'm studying the Lamport's Hash one-time password scheme. This is the scheme: Alice wants to authenticate herself to Bob from a workstation that knows nothing about her. Alice only knows her ...
4
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1answer
95 views

Are shorter password hashes safe?

How much can I shorten a password hash before it begins to impact security? Suppose that I use PBKDF2 (correctly salted) with HMAC-SHA256 as the PRF. From what I've seen, it's typical to use 256 ...
3
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1answer
131 views

Is it possible to reverse the birthday attack calculation?

I find that for every 100 password salts in our database, we only average 94.73 distinct salt values (averaged over a total of around 18 million). Is there a way to take that observation and calculate ...
3
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1answer
53 views

Attacks on WinRAR volumes reusing same password?

I have quite a few WinRAR volumes that are all encrypted with the same password. The password is long and unbruteforceable, but I recently read that WinRAR uses PBDKF2 as its key-derivation function ...
2
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1answer
317 views

XTEA: patterns in plain text

I'm using XTEA to encrypt passwords that I store in a database. (I need to be able to decrypt these passwords later to log in on another system.) But now I have noticed something: if I decrypt a ...
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1answer
108 views

Value of S and r in Fiat-Shamir Protocol

In the book Cryptography and Network Security by Forouzan,in chapter 14, Fiat-Shamir protocol, its mentioned that two large prime numbers p and q are chosen and kept secret. However n=p*q is made ...
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1answer
433 views

How long does it take to brute force a Wordpress password?

I'm not a cryptograhpy expert, I am a web developer trying to determine the origin of a Wordpress blog hack, and how likely it is that it was brute forced. The administrator account username had been ...
3
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1answer
555 views

Encryption algorithm used in WPA/WPA2

I want to know how EXACTLY the WPA password gets encrypted I have been searching through and I was able to catch: The actual password is converted to some hash Salting is applied to the hash The ...
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2answers
175 views

What are the required security properties for salts?

I was recently thinking about password hashing (maybe caused by the PHC progression). I started to think a little more about it and got stuck at this question: What security properties do password-...
2
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2answers
120 views

Client login without sending a password

I would love to have a system where the password is never send in plaintext (even with TLS) to authenticate a user. I've come up with this protocol, but I'd rather use something proven. Registration: ...
3
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1answer
621 views

Recommended password complexity for SSH key encryption using AES-256-CBC

When protecting SSH private keys with password-based encryption, what would be a good minimum password complexity+length standard to make cracking the password too difficult to be worthwhile anytime ...
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6answers
5k views

Is there a secure cryptosystem that can be performed mentally?

I, myself, do not plan on getting into a situation where I would be unable to use a computer in order to communicate securely. However, I can think of many practical situations in which mental ...
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1answer
164 views

Extension of a password hashing algorithm using Fibonacci

I am right now taking a class named Applied Cryptography and our final project is to create a password hashing method using at least one existing algorithm and then add additional steps to make it ...
3
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1answer
128 views

How can I generate a good password from a SHA512 hash?

I have to change local administrator passwords on machines. I don't want to store password in a database. I have to generate a password that I can find later to connect to the machine again. So I ...
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2answers
553 views

SHA-256 exhaustive search

How do I calculate the number of computations needed to break SHA256 in case we are using it for safely storing passwords (together with a salt)? Are there any formulas that can be employed? For ...
2
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1answer
68 views

Salting in asp.net?

I have spent the past hour reading up on salting and still don't understand how it is achieved. Forgive me if im wrong, but the way I am thinking of salting is, storing an ArrayList of random strings ...
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0answers
54 views

one complex password as a “seed” for localy generated per-service passwords

I've stumbled upon a project that suggests a way of having to remember one password, from which a “per-service password” could be generated by salting the service name using scrypt. What could be a ...
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1answer
73 views

About DH-EKE and ECDHE_PSK (PSK versus Pasword)

I am currently having a look at J-PAKE , so learning about Authenticated Key Exchange : Reading 2.2.2 E.K.E from this paper https://people.kth.se/~maguire/Erik_Ehrlund_Literature_Study_report_v1.2.pdf ...
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2answers
121 views

How much pre-hashing a password increase security against brute force attack?

I am wondering how much hashing a password used as key for a symmetric key algorithm helps preventing brute force attack on crypted text. Let's assume I want to crypt text A using key B using AES-...
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428 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 ...
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5answers
3k views

“123456” and “password” as crack standards

I know that when we encrypt, we use standard encryption technologies and to store data it's often stored as a hash. By encrypting a common password, for example "password" using ...
2
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1answer
235 views

Extracting a WinRAR password

If I have an original file and a WinRAR password protected .rar file containing that file, than can I extract the password?
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1answer
659 views

How many attempts does it take to crack a 32-bit password hash with this scenario?

How many attempts does it take to crack (match) a 32-bit password hash from a database of 4 million password hashes? Correct me if I'm wrong, but to crack a 32-bit password hash would take roughly 2^...
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2answers
63 views

Getting the encryption/has algorithm used for modem configuration file [closed]

Hello guys I have backed up my modem configuration file and found the username and password is in clear text; the files shows the username and the password is : ...
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3answers
287 views

How to quickly detect incorrect password in encrypted file without compromising security?

I am developing a software to encrypt/decrypt files/streams using symmetrical encryption algorithm. During encryption phase data wil be compressed and encrypted. When decrypting data, I want to be ...
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1answer
120 views

On countermeasures for replay attacks. Does this one require plaint text password storage?

I was reading this wiki section on the countermeasures against replay attacks and it basically suggests that: If Bob wants to confirm Alice's identity he can send a one-time token (I think it should ...
0
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1answer
108 views

What's wrong with an iterative (with counter) hashed salted KDF?

It seems like the brain-dead simplest KDF would have a key-stretching structure that is not substantially different from $\text{hash}(S | P | S | P |\dots|S|P)$, where $S$ is a salt and $P$ is a ...
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4answers
814 views

Why don’t all AES encryption tools produce the same key from the same password?

Alice and Bob meet regularly. They have agreed face-to-face a 128 bit password which they want use to encrypt/decrypt emails written between them. They decide to use 256-bit AES. Alice wrote her ...
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0answers
38 views

Registration and log in through public key cryptography?

I read about zero knowledge proofs. Let's say you want to create an account at a website. You choose a password $p$ and from $p$ you derive deterministically a public & private key pair $(e,d)$ ...
3
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4answers
475 views

Password length versus hash length?

If a system hashes passwords with a 256-bit long hash, are passwords (which are not necessarily alphanumeric, can be any value per byte (0-255)) longer than 32 bytes useless under the context in which ...
0
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1answer
68 views

How do I control an access code safely?

Upon registration an user has to specify an access code of five digits. This access code is also used as a password for the encryption and decryption of certain strings. The user types in "12345" (...
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1answer
52 views

Errata for NIST SP 800-63

I'm looking through the latest version of NIST SP 800-63, and there is a table (Table A.1) in the Appendix that supposed give the "entropy" of a password for a 94 character alphabet for various ...
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368 views

Generate secure password hashes without access to PBKDF2 or bcrypt

Given is a system, which does provide only implementations of fast hash algorithms (MD5, SHA1, SHA-256, SHA-512). There is no implementation of PBKDF2, bcrypt or scrypt available. The system does ...