Questions tagged [passwords]

Passwords are secret keys which human beings can memorize.

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Signal Key Stretching Regarding Their Blog Post

I just read this blog post (Signal - Technology Preview for secure value recovery) by Signal and something is not quite clear to me. In section "Stretching beyond a KDF" they generate a ...
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using TAILS OS to secure my password in veracrypt [closed]

thanks for taking a look at my post, i did a search and i couldn't find any information about this topic, so i thought i would post my question here. my question is this, i have recently learned that ...
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Is it safe to reuse the same nonce for decryption an indefinite amount of times in this context?

I'm creating a password management application and I'm considering using the following procedure to keep passwords safe: Asking the user for raw_password, for ...
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5answers
139 views

How passwords are fed to key derivation functions?

Suppose I want to encrypt data, send it over the network, and decrypt it on the receiver side. I know the elegant way to do this is by using a symmetric key to encrypt the data and an asymmetric key ...
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6answers
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Are longer passwords really safer against brute force attacks?

If we take two password strings of different length and attempt to bruteforce match them, it is obvious that the longer one will take longer to crack on average. However if we assume that when ...
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1answer
65 views

Choosing between hash functions instead of providing a salt for a password hash

I am working on some programs that require the users to store their passwords in my databases. However, due to the fact that I am not sure whether salt should be stored in databases due to my ...
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1answer
50 views

How slow is the hash used for Mac FileVault encryption?

Certain password strength estimators (for instance, zxcvbn) give estimates that vary with the speed of the hash and the assumed resources of the attacker. I am curious what hash is used by the MacOS ...
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How to securely store and validate a 4-digit PIN used on a mobile device?

I want to be able to securely (1) create and (2) validate a PIN, typed by a user primarily in a mobile app. There is no 'typical' password, although there is another 2nd factor. The starting point ...
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43 views

Two party protocol using only hash function

I have been told by my professor to compare two passwords as we do it in Yao's two-party protocol but without using any crypto functions. We are only allowed to use a hash function. The passwords are ...
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1answer
76 views

PAKE password change

Is there any way to change a password using a PAKE-like algorithm, without the server getting the plaintext of either the old or new password?
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Is it safe to use a deterministic salt as an input to KDF (Argon2)?

I'm prototyping an app that uses client-side password hashing in order to hide the "real" account password from a server (the server hashes any recieved password anyway, so no plaintext records in the ...
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1answer
98 views

What's the algorithm behind MySQL's sha256_password hashing scheme?

MySQL's old mysql_native_password hashing scheme was the equivalent of this in PHP: sha1(sha1('password', true)); That's a ...
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BIP32 Extended Key to EC Private and Public Key Pair

We are working on an application in Android using Java. In our project, we used to generate EC key pairs (of size 384 bits) using SpongyCastle - an old Android version of Bouncy Castle. The problem ...
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After downloading the Breach Compilation.torrent, how do I properly introduce new breach lists? [closed]

So I downloaded the Breach Compilation (the 1.4 billion usernames w/ respective passwords). When doing so, the friendly dev-like homies they are over @ github where the .torrent file for the latter is ...
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How hard is it to guess a 8 digit PIN?

Say that there are different live situations where you have to select own PIN numbers. Can someone say if it is possible to guess a 8 digit pin within 3 tries, given any methods or resources? Is ...
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0answers
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What is the formula to calculate password entropy? [closed]

I saw in another thread: Is using 7-8 random words from all words of a language as password a good idea? These calculations: If we assume that English has 171,476 words. Then with 8 words the ...
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2answers
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Advice in password auto-generation

I'm creating a program with key access for a determined term. I've made a code that will generate a key (password) with 16 characters length. The following information is encoded: initial date 6 ...
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3answers
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Is there a ready report about character order frequency in most common passwords?

There are charts about most used letters in English. What about the letter order? For example letter X has a bigger chance to appear than letter Y as the first character and something else for the 2nd ...
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1answer
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Is there a way to generate a password from another but those 2 will have no relation?

For example I have the password X and I want to encrypt 2 different things. Even if one of them was stolen due to a keylogger, other will be completely safe. I wonder how safe something like this ...
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Is using 7-8 random words from all words of a language as password a good idea?

The Bitcoin Bip-39 dictionary has 2048 words. And a random 24 of them are pretty secure together. What if the source is bigger (all words in the language) but there are only about 7-8 words? These ...
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1answer
133 views

migrate bcrypt -> argon2

We want to migrate our userbase from bcrypt to argon2. I was planning on an approach that migrates all hashes immediately to argon2; "old" users would have an argon2'd hash of their bcrypt hash of ...
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1answer
113 views

XChacha20poly1305 vulnerability to known plaintext attacks

During a security audit, the guy said our cryptosystem is vulnerable to known-plaintext attacks. He said that's because «the implementation uses a crypto_stream_xor() approach» (from libsodium). That'...
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1answer
78 views

Password to password mapping

DISCLAIMER: I understand the question might be a bit amateurish due to my limited knowledge of cryptography but, please, bear with me for a minute. QUESTION: Suppose a user Alice generates a pass ...
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1answer
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Generating nicer diceware passwords without losing entropy

Yes, another one of those "I have found a great password-generation strategy" waiting to be shot down! It seems that although diceware aims to be a secure and user-friendly password generation ...
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1answer
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just a question regarding passwords .computing the possibilities for a numerical PIN [closed]

How many possibilities for a numerical PIN with exactly 9 digits? How about a PIN with no more than 9 digits?
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Does the use of English words weaken diceware passphrases [duplicate]

A Diceware passphrase is constructed from a set of words chosen from a 7776-word database, using five dice throws to choose each word. The argument is that each word in the phrase adds about 12.92 ...
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5answers
268 views

Why are password database breaches bad if cryptographic hashes can't be reversed?

If companies such as Facebook store our passwords as hashes, when they are leaked how can this be a threat to the users? I thought of it because nowadays we do not have computational power to break ...
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1answer
109 views

pwd-hash like algorithm which can be computed on paper

"Common password problem" is well known problem, when user uses one password for many resources (web sites, logins to computers, etc...) For example, if one web site loses it' database, which contains ...
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1answer
52 views

About the security of GnuPG private key on-disk storage

GnuPG on-disk storage of secret key material is encrypted with AES-128, with an encryption key generated via an iterated and salted SHA-1 hash of the given passphrase. Is this usage of the SHA-1 hash ...
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86 views

Digital Signature Password verification

I currently have this TOFU protocol: First connection: Client generates salt and inputs a password Client saves salt Client hashes password with argon2 and salt Client generates Ed25519 keys Client ...
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2answers
538 views

Is using quantum computing to break passwords non-sense?

I understand the concept of 'trying all possibilities at once' but can anyone explain this with respect to the fact that my PC only accepts one password at a time? There's no input field that accepts ...
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801 views

How to validate a PBKDF2 password

I want to encrypt several files correctly with a PBKDF2 generated key (using a password and salt), I am currently doing so but if I enter the wrong password, as expected an exception occurs. Note: ...
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2answers
192 views

PBKDF and Entropy

We all regularly use password based, key derivation functions, however something that strikes me as counter intuitive is how PBKDF can somehow "stretch" the entropy of a supplied password to generate ...
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1answer
83 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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136 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 ...
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1answer
116 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 ...
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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 ...
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2answers
129 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 ...
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1answer
141 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, ...
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2answers
110 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 ...
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2answers
365 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 ...
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1answer
148 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 ...
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1answer
87 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 ...
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126 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 ...
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2answers
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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 ...
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2answers
37 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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136 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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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
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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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340 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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