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Questions tagged [passwords]

Passwords are secret keys which human beings can memorize.

2
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1answer
62 views

I don't want to store passwords, can I use them as an encryption key for another field?

I'm not a 'cryptographic' anything, so if this is a super-dumb question please let me know (politely). So here's the deal, say I don't want to store passwords because that opens me up to all sorts of ...
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2answers
72 views

Can an attacker exploit the nonuniform distribution of letters in a diceware password to improve a brute force search?

I use some diceware pass phrases in some places but I have one question that I can't find the answer to. Let's say I roll the dice and get $N$ words with a total of $M$ letters and that I don't put ...
-1
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1answer
49 views

Brute forcing/hacking Secure passphrases - difficulty for random strings vs real words

I was wondering about this topic of brute forcing passwords,or ANY other way to deriving them - and asking myself whats more secure (relatively): A Password which includes A) 30 digits length- a ...
1
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0answers
41 views

Time-based decryption service

i am thinking about building a public crypto service, yet at the same time, I am still quite new to crypto and therefore prone to snake-oil inventions I guess. My plan is to build a website which ...
-1
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2answers
106 views

Can you encrypt a 256bit password with a 256bit key so that it cannot be bruteforced?

Lets say we have an arbitrary but dictionary attackable password that is less than 256bit. (Lets just say the password is '1234Password'). We encrypt this password with a securely random 256bit key ...
0
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1answer
75 views

Storing passwords in a publicly available database

I have a public database where users need to store configuration files. The file can contain passwords. Everyone can read config files but only the server can read passwords in them. In the browser, ...
2
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2answers
68 views

Authentication without decrypting the password?

To my knowledge it works like this: The server receives the username-password values over a secure & encrypted channel. The username-password values are decrypted in the server and are present as ...
0
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2answers
87 views

Best practices for saving encrypted user data without a database

We are setting up a web application which requires users to submit sensitive data. Since entering all the required data may take a long amount of time, we want to give them the option to save their ...
3
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1answer
83 views

What is the most secure way to check that a given masterkey is valid?

For the purposes of learning, I'm writing a small utility that allows encrypting a list of passwords using a single master key (using AES-256 and PBKDF2) Before encrypting or decrypting any password ...
-1
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1answer
55 views

How many bits should I request from PBKDF2 to create a strong password?

I'm building a tool which generates passwords by hashing a service name with a master key. PBKDF2 was primarily chosen due to availability in the Web Crypto API. What would be a secure value for the ...
4
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0answers
49 views

Can “OPAQUE-over-TLS” authentication be optimized?

So while discussing the issues of password-hashing off-loading in our chat I noticed that it's easy to extend OPAQUE (CFRG draft) to essentially be a better standard password based authentication when ...
1
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2answers
64 views

Possible combinations of 8 digits, 6 upper case letters, 2 distinct numbers

Assume I want to find out how many combinations there are for a 8 digit word with 6 uppercase letters and 2 distinct numbers, e.g. A7BC9DEF, 1A0CRDEF, ... how many ...
2
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2answers
21 views

Mutual keys protection/wrapping

Is there a known risk in having two keys wrapping each other? Let's say, an adversary has access to both AESkey1(key2) and AESkey2(key1). Does it make it much easier for him to recover the keys?
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2answers
74 views

Where is the password hash calculated, locally on or the server?

My computer security professor uses the following notation, where S denotes a server and A denoted Alice. Alice wants to authenticate herself to the server. The hash function is a hash chain where $h^...
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2answers
283 views

64 bits password = 13 characters?

If we use upper and lower case letters, and 10 digits, we get approximately 6 bits per character. Then, strings of 13 characters should work. I saw above explanation in the material, but I cannot ...
2
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1answer
605 views

Difference between SSHA512 and SHA512

I am using SSHA512 to encrypt email user's passwords. Manually doing this works using doveadm from dovecot. But I can't seem to implement this in my mail client. I can, however, use SHA512. Is ...
1
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3answers
313 views

Password re-use by another person or on another service

How does having the same password in different services make it less secure? How does having the same password as someone else make it less secure? Very basic question that I've always wondered about; ...
2
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2answers
78 views

How may passwords are available to use in this scenario?

Password string consisting of one or more of the 26 characters A..Z and can be of any length from $1$ to $8$ characters. How may password available to use this scenario? As my calculation, it should ...
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1answer
1k views

Decrypting SHA512

I was recently solving a CTF problem and it involved a shadow and passwd file. I got to know the username easily but I am unable to find the password since it is SHA512 hashed. My doubt is that when I ...
1
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1answer
139 views

How to prove that a rainbow table is complete?

Passwords that are hashed but not salted can be cracked using the rainbow table. I went through this and this which explains the logic behind rainbow table very well. But I am missing something about ...
15
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2answers
5k views

Calculating entropy within xkcd 936: Password Strength

When I calculate entropy for the xkcd Password Strength (comic 936) I don't get nearly the amount of entropy stated in the comic. So why doesn't the the first password "Tr0ub4dor&3" have an ...
3
votes
1answer
64 views

Secure password-authenticated key exchange that allows for passwords to be stored as hashes, but does not make the hashes password-equivalent

Are there any secure password-authenticated key exchange that allows for passwords to be stored as hashes, but does not make the hashes password-equivalent? This would be useful for many ...
3
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1answer
56 views

Does it make sense to have long SSH Key with shorter Passphrase?

If we encrypt our data with a longer SSH key which is protected by a shorter passphrase (with a decent entropy), then the limiting factor is entropy of the passphrase. So why do we use a longer key at ...
0
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1answer
278 views

Having trouble understanding reduction functions in rainbow tables

I'm continuing doing some personal research on rainbow tables, but forsome reason I cannot understand how to choose the correct reduction function. Wikipedia states that "Only when the attacker has ...
1
vote
1answer
104 views

Hardware, Handheld Password Manager

I am currently working on a hardware project that will utilize the native USB and keyboard emulation capabilities of the Teensy device. Essentially, the user will store an encrypted password database ...
3
votes
1answer
191 views

Is using a smart card and password two-factor authentication?

I use a smart card - as read only device - for user identity as well as a password: The smart card (holds the user ID) is something I have; The password is something I know. Is this still two-factor ...
0
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1answer
138 views

Avoid decrypting every password in a password manager

The Setup I'm making a password manager for fun. It stores a random encryption key, encrypted with a key derived from the master password, and then it stores the data, which is a list of (site, ...
0
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3answers
299 views

Recommended minimum entropy for online passwords in 2018

Assume a simple case, that an attacker knows the password creation scheme, and that we're not dealing with state actors, nor with sites which keep passwords in plain text. We're trying to defend ...
0
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2answers
85 views

Client-side password stretching - danger of the salt being public?

In case of using client-side password stretching (plus a single hash on the server) - the server would need to send the salt before authentication, of course. Though the salt is not considered a real ...
3
votes
2answers
96 views

Are PBKDF2 derived keys related if only the number of iterations is changed?

I'd like to encrypt my disk with a password. To generate a nice key from a password, I used PBKDF2, which applies a hash function $k$ times to a cleartext and outputs the final result. When I ...
2
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3answers
136 views

Two salts, One password

If I have two different MD5 password hashes with two different salts (the salts are known), is there any way to cryptographically deduce if the two passwords match? Other than brute force password ...
0
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1answer
62 views

Quantum security risk to present encryption

Quantum computers will seal the fate of conventional encryption techniques. Of these, the hardest hit will be the RSA algorithm used by 99 percent of all applications the encryption standard for any ...
1
vote
1answer
72 views

Is a singular LUKS volume with different passwords that unlock different filesystems possible?

So it's hard to make sense out of the title. Let me elaborate: In LUKS, you can have multiple passwords that unlock the same volume (due to their "unified key setup" where they have a single master ...
2
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1answer
63 views

Password protection in ARJ: 3 characters of password are retrievable

On this site there is information that one can know first 3 characters (bytes) of the password without brute force. I know that ARJ in older versions has very simple encryption, i.e. XOR with ...
0
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1answer
111 views

Padding vs Hashing Encryption Key

I am making a program for personal use that will not contain super-sensitive information. I am using this to explore cryptography. Would it be acceptable to use a password to generate a key for AES, ...
6
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3answers
275 views

Bounding security of password authentication given entropy

An adversary Craig tries to log-in as Alice on a system that will only accept the right password, leaks (only) if an attempt succeeds, and allows many attempts. Alice's password choice is modeled as ...
1
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2answers
80 views

Hashing login and password?

For a login the user credentials are typically some form of "username" and a matching "password". The password is (hopefully) stored as a hash in the database. But what about the username? Is the ...
1
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2answers
143 views

Zencash uses your passphrase to identify AND unlock a wallet - how is this secure?

When looking into Zencash I stumbled into myzenwallet.io (by the Zencash creators), which gives you the option to enter a passphrase to generate a wallet (seems normal), but then after creating your ...
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2answers
133 views

Security of password hash with known prefix and appendix

Assume I have a password that is exactly 32 characters long. I hash it the following way: Prepend 1524 bytes (known to an attacker) Append 3356 bytes (known to an attacker) Do the checksum It is ...
3
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1answer
176 views

aWallet Password Manager

After reading a lot of articles on ramping up the security of my web accounts, I started using aWallet Password Manager for Android to backup my passwords. I like ...
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1answer
146 views

Safety of having many passwords hashed with the same salt?

I'm working on a web application where passwords must be hashed on the client before it can be send to the server. This is because the user's raw password is used for cryptography purposes and can't ...
0
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1answer
948 views

How long will brute force of salted SHA-512 hash will take, if salt is known and possible characters in password are known?

Suppose I know that the password is composed of characters [A-Za-z0-9], length is unknown, but maybe less than 8. If I have information about the salt use to perform hashing, and also hashing ...
1
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1answer
35 views

Expanding truly random key into printable password for successive hashing

The STUN network protocol defines its client authorization in the terms of message-integrity check employing the following scheme [RFC5389, section 10.2]: $$ \DeclareMathOperator{\HMAC}{HMAC} \...
2
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2answers
120 views

Salt passwords with the username?

Salts should be unique so that an attacker can't brute force multiple passwords at once. However, since usernames are unique, wouldn't it be possible to use some representation of the username as a ...
1
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1answer
103 views

SCRAM Iteration Count Attack

I'm not sure if this questions belongs here or in the Information Security Stack Exchange, but here goes... With SCRAM (RFC5802), is there anything that prevents an attacker masquerading as the ...
2
votes
1answer
148 views

Benefit of capitalization when using Diceware passphrases?

If I use a Diceware generated passphrase of any given length, will capitalizing the first word (or any word for that matter) effectively double the number of combinations that would have to be tried ...
2
votes
2answers
550 views

How do I calculate a password space if the password only has eight alphabetic characters (not case sensitive)

I read this wiki article and saw this formula for random password's information entropy. Also the wiki article mention that the symbol count for non case sensitive is 36. Is there a way I can ...
3
votes
4answers
218 views

How many bits of entropy are leaked for every derived password from a master?

Given a master password that has a lot of entropy (similar to Bitcoin HD wallet seed words, 130 bits of entropy or more) how many bits of entropy are lost per leaked generated password? Let's take an ...
3
votes
1answer
288 views

Diffie-Hellman based password challenge response scheme

A very commonly used (examples: HTTP digest auth/CHAP/Kerberos) authentication scheme is something that looks like: Setup. Client and server both know a password $p$. Authentication. Server sends ...
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1answer
87 views

For WinRar, how long should a password be to make up for a lack of complexity?

Assuming that the best alternative to complexity is length, how long do you recommend a password or phrase to be when using WinRar? Note that I'm aware that it's not always that simple, but I would ...