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Questions tagged [passwords]

Passwords are secret keys which human beings can memorize.

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2answers
543 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 ...
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1answer
2k 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 ...
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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 ...
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3answers
318 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; ...
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4answers
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Is there a practical way to crack an AES encryption password?

I heard that the fastest method to crack an AES-128 encryption, or and AES-256 encryption is by brute force, which can take billions of years. But I can't help thinking there's got to be a faster way. ...
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3answers
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What is the recommended number of iterations for Argon2?

I've recompiled my operating system ("LionBSD" based on FreeBSD) to use Argon2i as the default password hashing algorithm in crypt/libcrypt. I'm wondering what the recommended number of iterations ...
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1answer
3k 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 ...
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1answer
191 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 ...
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2answers
6k 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 ...
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5answers
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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 ...
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1answer
95 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 ...
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1answer
423 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 ...
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2answers
482 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 ...
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1answer
243 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 ...
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1answer
252 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, ...
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1answer
391 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
139 views

Stateless user-generated one-time passwords

I've been working on my course project lately and got stuck with the problem which I reduced to the following abstract protocol: Alice generates an ID key and gives it to Bob. Bob generates some ...
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1answer
129 views

Is there a term for “bootstrapping” encryption by storing an encrypted key?

Say you want to encrypt a large file, perhaps a backup of a database. Encrypting the file will naturally take some time, due to the amount of data. Now, if at any point you want to change the ...
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1answer
78 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 ...
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2answers
97 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 ...
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2answers
177 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 ...
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3answers
163 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 ...
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1answer
136 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, ...
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1answer
63 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 ...
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1answer
98 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 ...
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1answer
203 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 ...
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2answers
93 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 ...
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1answer
534 views

Commutative Hash Function for Password Challenge?

I had an idea. Could anyone tell me if this is a thing, if they see any problems with it, and if they know of a commutative hash function that would make it work? Suppose you had a pair of ...
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2answers
160 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
155 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 ...
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1answer
242 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
2k 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 ...
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1answer
38 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} \...
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1answer
372 views

Any point to AES on password with hardcoded key?

I'm inheriting a project that stores a used password in a config file, which is generated by the user giving their password in plain text, and the project giving back a key generated through .NET's ...
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2answers
151 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 ...
2
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1answer
789 views

Encryption in popular compression file formats - 7zip, RAR, Zip

When encrypting a file say with Winrar you have to enter a password. I am under the impression that this password is not stored anywhere but instead the password together with some other attributes ...
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1answer
156 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 ...
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1answer
202 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 ...
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4answers
264 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 ...
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1answer
89 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 ...
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1answer
1k views

Use sha3 for passwords hashing

Is use of sha3 justifiable? Is sha3 better than sha2 in (m)any aspects? P.S. I want to use hashing for passwords in a database
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2answers
728 views

HMACSHA1 vs HMACSHA2 (for PBKDF2)

I need to choose an HMAC function for PBKDF2. I'm using .net so I don't have the option to use SHA3. At first glance, and according to this answer by Thomas Pornin it seems like SHA512 would be best....
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1answer
343 views

Why is password recovery so slow for Whirlpool hash, when compared with others?

I'm just curious about why brute force takes so much longer on the Whirlpool hash than it does on the others, as you will see below: ...
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1answer
193 views

Does this PBKDF2-SHA1 payload hint at a cryptographic security issue?

Blockchain first 16 encrypted bytes, IV, and iter_count – all encoded in Base64: Yms6xqrzCfFsQadVZ5gQonMtnQAAAAAAAAAAAAAAAAAAAAAQJwAA69tYNg== Does it looks like “...
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3answers
2k 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
359 views

Comparing different hashes to confirm they came from the same string

Is there any safe hashing algorithm that returns a different hash each time (like bcrypt) but has the possibility to compare 2 different hashes and determine that they were hashed from the same ...
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0answers
132 views

Jumblar: Using map locations as passwords [closed]

I had the idea of converting map locations into passwords. Basically Jumblar (github.com/micheal-swiggs/jumblar) takes a hash of the user's location and stores this as a comment on the PGP network. ...
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1answer
110 views

New Passwording? [closed]

I just want to note before you continue reading--this does not specifically apply to hashes or the key to encrypted messages. However, I am initially thinking about password/key solving/remembering by ...
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1answer
115 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 ...
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2answers
2k views

Password hash that can be upgraded without plaintext password

Most password hashes have a cost parameter that indicates how long the algorithm should take. Is there an algorithm where you can increase that cost for a particular hash, without access to the ...