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Questions tagged [passwords]

Passwords are secret keys which human beings can memorize.

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0answers
23 views

Is it possible to convert hashed password from one bcypt version to another?

I have passwords hashed using bcypt version \$2a\$ (e.g. "\$2a\$06\$...") and I want to convert them to version \$2b\$ (e.g. "\$2b\$06$..."). Is it possible to do that? If yes, are ...
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Password hash contained '\x00' in middle, resulting in ValueError from bcrypt.hashpw

I have some code that accepts a password in string format, and hash it with SHA3-512 before passing it to bcrypt for hashing. However, by some coincidence, I found a test case that produces a hash ...
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2answers
318 views

7-Zip Encryption: Practical Effect of Lacking Salt

A previous discussion on Cryptography StackExchange leads me to understand that 7-Zip does not use salt to derive an encryption key from password to use its AES-256 encryption; that this is a ...
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2answers
155 views

Would hashing a password twice prevent naive attacks?

A common way of using MD5 or any other hashing algorithms to store passwords is to hash the password with a salt $$\text{hash}(\text{password} \mathbin\| \text{salt}).$$ This way, if an attacker wants ...
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1answer
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BIP 39: If I mix my 24 seed phrase with another 24 words, will the checksum property allow an attacker to retrieve the original seed phrase?

Assume that I have a 24-word passphrase that I want to store securely but online by mixing it with another 24 words in a manner only I know. Does the checksum property somehow help an attacker to ...
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2answers
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Why does the PAKE ideal functionallity allow the keys to be the same when the passwords differ?

My intuition for the security a symmetric PAKE is supposed to provide comes from the example of a login page. Both the user and the server know the password (assuming unhashed passwords), and the ...
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1answer
80 views

In Microsoft Password Monitor implementation using HME how do they perform ComputeMatch Function?

https://www.microsoft.com/en-us/research/blog/password-monitor-safeguarding-passwords-in-microsoft-edge/ In this they mention The server then evaluates a matching function on the encrypted credential,...
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1answer
50 views

Do I need a salt for Scrypt if the data is client-side?

I have a web app, in which I am encrypting user data client side. Each client has their own password, which is used to derive an encryption key (via Scrypt) for encrypting their data. Since the data ...
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1answer
328 views

Is tagging the hash of a password along with ciphertext secure?

Suppose I have a password, in which I use Argon2ID with 1GB memory to derive an encryption key. Then, I encrypt my data using XChaCha20 using that encryption key. The problem with ChaCha is that any ...
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Dragonfly masked DH

I was looking at Dragonfly key exchange protocol RFC 7664, and it seems to make use of masked Diffie-Hellman in the final part. Generating two random numbers less than group order $q$, $m$, and $r$ ...
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Why do some people believe that humans are “bad at” generating random numbers/characters like this?

I'm not even sure if they are serious, but I've heard many times that some people refuse to not only trust their computer to generate a random string (which is understandable) but also don't trust ...
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How long would it take all of the supercomputers or cloud computing on Earth to bruteforce a significantly long password?

I was arguing with a colleague who thinks that SHA256 (password + 64 character static salt) is "insecure." My argument is that nothing in cryptography is "secure," it's all a ...
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61 views

Is this method of salting effective?

So this is my first post on this forum, so bear with me if I sound stupid. I am creating my own web application with JavaScript and MongoDB. I am storing all user information in a Mongo table, and ...
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1answer
84 views

Can ECDSA signature signing and verification process replaces password hashed based login system?

ECDSA or DSA in general was to sign a message or data using private key and verify it using public key, if the attacker/imposter doesn't have the private key then they couldn't sign the message ...
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1answer
58 views

Where to obtain a common/weak password list (black list)?

The NIST 800-63B publication specifies recommendations regarding memorized secrets (passwords) https://pages.nist.gov/800-63-3/sp800-63b.html#memsecretver specifically section "5.1.1 Memorized ...
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Number of combinations with a max. of successively repeated characters

I would like to calculate the possible password combinations for a password that is 60 characters long, has the letters a-f and numbers 0-9. Also no character should repeat successively more than 7 ...
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What is the purpose of hashing the identifier in the secure remote password (SRP) protocol?

In the secure remote password protocol version 6a, the identifier for the user, I, is hashed along with the salt and the password on the client. While I understand ...
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1answer
69 views

Is this mentally computable password system, cryptographically secure? And anything like this out there I can find?

Please bear with me on this, I'm not learnt in this field, just trying to ask questions about the security of my encryption method. I'm trying to create a mentally computable human password manager ...
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2answers
308 views

Recovery Passphrase Collission for BIP-39 and BIP-44

Referring to the standards of [BIP-39] and [BIP-44]: a 'master password' consisting of 12 words uniformly selected from a 2048-word dictionary corresponds to 128 bits of entropy, that is then used as ...
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0answers
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What grade of protection does a private key's passphrase provide at best?

Does a passphrase with high entropy provide the same level of security as the private key itself? General scenario: An attacker has access to a private key file that is protected with a passphrase ...
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2answers
50 views

How to be able to change the password to access data encrypted with AES-GCM, without reencrypting?

Let's say you need to encrypt plaintext which is 1 TB big. You have a password pwd. This very classical AES-GCM process is ...
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3answers
294 views

Why is SHA256/SHA512 not broken for shortish passwords

I don't get why SHA-256/SHA-512 hasn't been broken, at least for shortish (10-12 character) passwords It is perfectly plausible to pre-compute a password/hash-pair table using numerous very fast ...
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Is my password database encryption flow secure?

I'm not an expert and I would be very glad if someone could take a look at it and tell if there are any problems with it Things I know/think are problematic using base64 digest + getting the first 32 ...
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1answer
58 views

Are there any methods for constructing a password that can be reconstructed if forgotten and is as secure as randomly generated ones?

Is there a formal name for such a thing, so I know what to google? Is it possible to make them as secure as randomly generated passwords? An illustrative example would be something like picking a ...
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Should I use 2x the number of CPU / core for Argon2id parallelism?

I've read that I should use 2x the number of CPU available from some documentation while others suggest using between 1 and the number of CPU. I realize there is no hard answer here but I'm curious ...
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Generating traceable passwords

I'm new to cryptography, so please bear with me as I try to explain what's going in my head. I have an idea to write a program to generate one-time passwords for online conferences that are although ...
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1answer
163 views

Is this password-cracking challenge possible?

Taking a graduate computer security class, part of our current assignment is to crack 50 Unix md5crypt password hashes, due on Thursday, October 8th (in eight days.) I've managed to crack 49 out of ...
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What can be deduced/extracted from this local hash extracted from Windows Machine?

I'm new to cryptography. I've been experimenting with getting Windows hashes to see whether it's possible to reverse engineer. The following hash is what I got from my test laptop. What can you ...
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1answer
324 views

How to choose parameters for Argon2 for password vault

I'm creating a password vault and I'm planning on using Argon2id to derive the master key from the master password. For encryption I'm planning on using XChaCha20 with Poly1305. To be clear: a set of ...
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1answer
95 views

Is this cumbersome strategy to produce a ridiculously strong password valid?

I'm writing something where somebody wants to have a ridiculously strong password for a file and yet be sure that he will always be able to reconstruct it. The way I have thought of this might be a ...
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Cryptography elements needed for a story

Note: following Maarten Bodewes's answer, I edited this post to make it clearer. I'm writing something partly driven by the need to crack a few encrypted files. This is what needs to happen in the ...
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Good layperson analogy for password and encryption keys

NOTE: QUESTION UPDATED. SEE BOTTOM OF THIS POST. I'm writing something where I need to make someone come across as though they know cryptography. I don't know enough, but as cryptography plays only a ...
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How to calculate the entropy for a fixed length random passwords which has restrictions on the type of characters used

If we have a set amount of usable characters, but no other restrictions on the potential characters in a completely random fixed length password, we can easily calculate the entropy by doing: $\log_2(...
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1answer
205 views

Is storing salts encrypted a good idea?

I've read that storing password hashes in a database, you can store the salt in plaintext alongside the actual hash with no detriment to security. I was thinking that one could derive a key from the ...
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Could someone please explain the implementation of public-private key encryption for storing passwords?

As someone new to cryptography,I have a question about how logins work on websites. I understand mathematically how asymmetric encryption works and how https web requests work to securely send ...
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1answer
72 views

How to provide secure password based encryption with password reset option

I am trying to build website that will encrypt some data for the user using his/her the output of scrypt on it, now the idea is that this schema is not flexible because if the user loose their ...
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1answer
111 views

What kind of a strategy can be used to crack this password?

The password is 11 chars. It has 5 letters and 6 numeric characters. There is at least 1 uppercase and 1 lowercase in it at the same time. Can an attacker benefit from these information even though he ...
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1answer
76 views

Combining algorithms for password storage?

Is it more secure to combine algorithms for password hashing, for example, Scrypt, Bcrypt, SHA-3, etc.? If an attacker wants to use dedicated hardware, he would need one for each algorithm. However, I ...
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1answer
257 views

Can you correct my understanding of Argon2? [closed]

I'm a bit new to the cryptography field (completely new), and could really use your guidance. Please, correct my understanding, as defined by the following statements. The ...
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Relation between Zoom id,password and join URL [closed]

We all are using zoom application for joining/hosting meetings in this corona virus period. As we create a meeting, a new id, password and a url is generated. Some real examples follow- Id: ...
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1answer
121 views

Do all PAKE assume that all parties already have a password?

I was looking for a means to perform a key exchange without relying on a PKI. I discovered Password Authenticated Key Exchange (PAKE) and after reading J-PAKE; I have the following questions: Do PAKE ...
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2answers
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Just how insecure are VeraCrypt containers encrypted with short passwords?

When I create a VeraCrypt file container using the GUI, it displays a warning whenever I type in a password under a given number of characters. I was wondering just how insecure, in practical terms, ...
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1answer
149 views

how many iterations of SHA3 (keccak256) hashing would be required to provide reasonable protection for the following data structure?

((A , B , C) , (D , E , F, G, H)) Where: A is 0x0-0xF, (1 of 16) B is 0x00-0xFF (1 of 256) C is an 8 digit integer D is a one of a list of one hundred words padded to 12 characters E is a one ...
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1answer
53 views

Secure password reset

In my model I use two different keys, one for authentication and the other for the encryption / decryption of the data that the user saves, each derived from the master password with a KDF function. ...
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2answers
221 views

How much entropy do I need to add to passwords if they are NOT used in conjunction with logins

I'm building a system to authenticate users to a website via a single use login token. This token can either be included in links OR typed in directly by the user as a code. Because of that second ...
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102 views

For uniterated SHA-256 of salted password, should the password precede the salt?

This is a follow-up to this question (thanks to answers from @fgrieu and @kelalaka ) about the format of a salt when hashing a salted password. I realize this is pretty much academic, as the proposed ...
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2answers
258 views

What format should a salt be when it is concatenated with the password?

Assume that, in the available environment, it is not possible to use modern password hashing functions (bcrypt, scrypt, Argon2, PBKDF2, etc.), so it is necessary to roll my own stand-in, until they ...
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1answer
179 views

Does pepper *require* an HMAC?

Assume you are already given a properly-salted, password hash $X$ from some slow PBKDF (e.g., like Argon2id). Now, you want to apply some large (~256-bit) secret "pepper" $S$ to it before storing it ...
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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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1answer
308 views

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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