Passwords are secret keys which human beings can memorize.

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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 ...
0
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2answers
34 views

Using password-based encryption as a hashing scheme

Classic scheme: Given password and hashing algorithm Generate salt Calculate ...
1
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3answers
51 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 ...
2
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5answers
2k 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 ...
1
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1answer
63 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?
0
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1answer
218 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 ...
0
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2answers
33 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 : ...
1
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3answers
155 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 ...
0
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1answer
60 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
25 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
45 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 ...
0
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4answers
192 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 ...
0
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0answers
35 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 $(e,d)$ ...
2
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4answers
106 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 ...
21
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4answers
16k views

Can you help me understand what a cryptographic “salt” is?

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 anyone offer me a ...
0
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1answer
59 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" ...
1
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1answer
45 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 ...
1
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2answers
130 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 ...
9
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1answer
4k 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 ...
0
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1answer
75 views

What is the proper way to generate a fixed length key from a variable length password?

The password is entered by the user and the key is processed locally. Neither the password nor the key will be stored, only used and forgotten (but hopefully not by the user). Is SHA256 by itself ...
1
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1answer
114 views

Creating a random password based off of a prime number

So I am making an application that basically creates strings that must be encrypted before they are stored on a user's device. If the user blindly starts running the application without creating a ...
0
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2answers
113 views

Removing “security by obscurity” from port knocking

Every article about port knocking, for instance https://wiki.archlinux.org/index.php/Port_Knocking , declares this method as security by obscurity. Is the following enough to remove that title; a ...
1
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2answers
164 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 ...
0
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1answer
60 views

Are passwords generated from sine vulnerable to certain attacks?

A friend mentioned that he used the sine of a number, i.e. sind(54), to generate long passwords. This way he only has to remember sine 54 and have a calculator to get his password back. I am wondering ...
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2answers
47 views

Automatic generation of secure passwords with the least inconvenience for a user

I'm working on a web site for a private company that should allow them to upload files, which will be later retrieved by their affiliates. The site will be available from a public Internet using ...
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0answers
26 views

Any ideas on login using Digital Signature PKCS

I am curious to know about possibility to login into web application just by identifying the user based on digital signature in usb token. any reference in this direction?
39
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3answers
16k views

How should I calculate the entropy of a password?

If part of the password is a whole regular English word, does the entropy of that part depend on the number of English words in existence, the number of English words known by the choosing algorithm, ...
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0answers
82 views

How does multi platform encrypted cloud storage work?

I'm really interested in end-to-end encrypted cloud storage and couldn't find out how following scenario could work: A user of a cloud provider which provides zero-knowledge-authentication (like for ...
0
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3answers
290 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 ...
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2answers
107 views

Is there a client-side program to cryptography a HTML page and decode if correct password is writen? [closed]

I want to know if there is an easy way to do this: create a complete HTML page cryptography the text content (image is not important) ask user some password check the password with a cryptographed ...
0
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1answer
51 views

Adding a Password Hash (key derivation) function to existing password storage solution

As always we are trying to improve password storage; before just adding new ways of storing our password we need to define what threats we will mitigate by adding in a new way to store our password. ...
8
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1answer
636 views

What are the security implications of multiple hashing?

There are plenty of questions on this site about hashing passwords. However, none of them quite cover this topic. One of those links covers using multiple different hash algorithms; one covers general ...
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1answer
63 views

Protecting a short password

I figured that a really secure password would be an AES 128 key. If this key were to be base 64 encoded, I could replace 4 random bytes in it in order to make it unusable unless you know which bytes ...
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0answers
37 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 ...
4
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2answers
1k 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 ...
0
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0answers
112 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 ...
8
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2answers
217 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
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0answers
49 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 ...
0
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2answers
127 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
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2answers
120 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
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0answers
71 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
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1answer
134 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 ...
6
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1answer
323 views

Single-purpose symmetric encryption scheme for single files

I'm writing a simple password manager program that will encrypt/decrypt a single file (it's size will most likely stay under a few K). This is my initial file format design: ...
2
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1answer
172 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
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1answer
379 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
1k 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
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1answer
191 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 ...
3
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1answer
147 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
1answer
139 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 ...