Passwords are secret keys which human beings can memorize.

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Is public-key cryptography the only option in this scenario?

Two parties: a client and a server are to a agree on a symmetric key. Both the client and the server are aware of a master password. The way this is currently done ...
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221 views

Can a “pattern” in a series of passwords be detected from their hashes (and maybe a single raw password)?

Let's say I'm a lazy user of a system with annoyingly frequent password change policies. I may have a "good" password I used initially that is only used for this system but since I have to change it ...
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267 views

Crypto USB Devices - where is the PIN/Password stored?

I am currently looking at the security of cryto USB drives for storing x509 certificates. I have one in possession currently. It can be read/written to using the Microsoft Crypto APIs. Anytime one ...
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95 views

Secure Sketch Construction

I would like a user to choose a point on an image which is represented by (x,y). This is meant to be a security token. When a user uses this location to login they are unlikely to to choose the exact ...
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1answer
360 views

Can I secure my key by XORing it with a hashed password?

I'd like to build a simple password-protected symmetric key system. The key-creation process in my system operates as follows: The system creates a 256-bit key purely at random. The user chooses a ...
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495 views

Passwords with same SALT. What does this mean?

If the same SALT is used for many passwords on a Linux server, in what way is that a security risk? Does the mean, that a user (which can change his own password) can calculate other users passwords? ...
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1answer
86 views

Calculate entropy of key derived from PBKF2 function

I am using PBKF2 to derive a encryption key from a password. suppose entropy of my password is y and my PBKF2 function has x number of iterations. So how to calculate the entropy of finale key derived ...
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1answer
1k views

Decrypting the password from SHA-512 hash value

I am currently studying AES algorithm and writing a Code using Python. I am trying to add 'Salt' into the user input password, Here is what I am doing, ...
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1answer
199 views

What's the most secure way to derive a key from a password repeatably?

I'm trying to write a cloud storage application where everything the user uploads is unreadable by the server, encrypted client-side before being sent. Currently, the flow looks like this: User ...
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811 views

Hash function in PBKDF2

From this excellent answer I learned (correct me if I am wrong) that when writing a block cipher with say key size 128 bit, one has to pad the password given (variable size) so that it becomes exactly ...
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1answer
352 views

Recommended way of adding a pepper/secret key to password before hashing?

There have been several questions regarding password hashing here and on Security.SE. A "pepper" is sometimes mentioned – an application-specific secret key. The canonical answer on password hashing ...
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375 views

estimate of time required to crack sha512crypt password with JtR + OpenCL

OK, I have a shadow file with a password that I know, it is 4 letters followed by two numbers. Using John The Ripper with OpenCL support, on a laptop with AMD Radeon Mobility graphics, how long would ...
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661 views

A single password manager vs password generator/hash

I have been wondering about the options available for managing passwords. However, they all seem to fail if the master password is compromised (which isn't a big surprise). On one hand you have ...
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1answer
178 views

Seed a PRNG with random data and a password

I'd like to combine a random key file with a password to generate a secure seed for a CSPRNG. The key file is assumed to have very high entropy, but the password will be whatever the user provides. ...
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1answer
476 views

What happens to the entropy of a password when you hash it?

For example, if the entropy of a password is 30 bits, what is the entropy of the password when you hash it with MD5?
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1answer
424 views

How can I generate a one-time password?

Through my reading about the generation of one-time password (OTP) I found that there are many algorithms that generate OTP and they are either based on time such as TOTP or based on mathematical ...
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1answer
154 views

Is a changing public truecrypt container secure?

I have a Truecrypt container which I want to synchronise between computers (i.e. different people, that I want to share the data with). If I used Dropbox for synchronisation and someone downloaded ...
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2answers
323 views

Adaptive Hash Functions: How to tell how many iterations were used?

If an adaptive hash function like bcrypt or PBKDF2 is used in hashing passwords, the number of iterations used in the hashing process can be configured. For a penetration tester or a malicious ...
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193 views

It is reasonably safe to leave a SSH private key with a 30+ character passphrase public?

I'm curious about exploring uses for a distributing a single RSA private key with a passphrase instead of trying to secure the private key and distribute the public key. With the private key (and ...
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1answer
72 views

Rapidly changing passwords?

Suppose you need to authenticate yourself to a program with the password - but the program's source code is public, the program doesn't have access to any private information and all your ...
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1answer
97 views

password generation: random length or max length

In short: Is it cryptographically stronger to have a known length password of the maximum length allowed, or a random length password somewhere in the range of the longest length possible? Does the ...
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2answers
225 views

Could completely public passphrase hashes ever be reliably secure?

This is a hypothetical question and I only have a basic understanding of Cryptography. If one were to follow the very best cryptographic practices for storing passphrases, could it ever be possible ...
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2answers
204 views

bcrypt and pbkdf2 double hashing

If I want to protect myself from implementation of algorithm issues and inherent design flaws of algorithms in password hashing, what would be most secure way to combine two hashes? ...
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2answers
309 views

Is rainbow table attack applicable to any hash?

Typically when rainbow tables are discussed MD5 hash is used as an example. It's not quite clear whether this attack is specific just to MD5 or to a certain subset of hashes or to just any hash ...
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1answer
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Bcrypt VS Scrypt, Again?

I found this article on SO, but the answer was short, and the subject was closed, What i don't understand, is: Which one of the two limits memory usage to avoid custom Hardware to break the password? ...
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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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1answer
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How does the possible attack on passwords and salts mentioned in PKCS#5 v2.1 work?

From PKCS#5 v2.1, 4.1 Salt (page 6, emphasis by me), also in v2.0, RFC 2898: In password-based encryption, the party encrypting a message can gain assurance that these benefits are realized ...
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1answer
112 views

salting with password hash to improve security?

Would something like the following improve security (against rainbow attacks, not brute force)? Assume that $P$ is a user-chosen password, and the objective is to obtain a hash $H$ for password ...
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200 views

Commutativity of keyed hashes

Definition ${H_1}^{K_1}(X)$ means data $X$ hashed by keyed hashing algorithm $H_1$ with key $K_1$. Short question Is $H_1^{K_1}(H_2^{K_2}(X))$ equal to $H_2^{K_2}(H_1^{K_1}(X))$? Is ...
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1answer
654 views

Ideal passphrase length: old diceware method (5 words) vs. your Bitcoin wallet.dat passphrase lenght (8 words) and doubling passwords?

I made a cool 5 word passphrase back then using the old Diceware method and use it as a master password. The question is as computing power increases will we need to add more and more words to our ...
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1answer
2k views

Is AES restricted to only 64 characters for the key/password?

I am wondering if AES only supports 64 character passwords? When using truecrypt, the maximum character limit on passwords is 64 characters; however, when using WinRAR, the limit is 128 characters. ...
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2answers
172 views

How can I store a combination of multiple pass phrases?

Let's assume we have 2 phrases, one is the real password from a user, and the other is generated from the real password and almost impossible to guess. You would need both to authenticate a user. What ...
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1answer
159 views

2 comparable hashes generated from one string

Assume a website where people log in with their password. The password is now stored in sql database as: md5(password + random_salt) We are adding the ...
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232 views

Assymetric password encryption - Viable? Which algorithm?

We have an application that requires cleartext passwords for user authentication because of the authentication mechanism in use (RADIUS/CHAP), which unfortunately we cannot change. Since we don't want ...
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Attacking hashed password by timing attack and other means

This question is inspired by this recent one, which raises a point that need to be made quantitative to be meaningfully discussed. I chose an unusual approach: a new question worded as homework that ...
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Integer factorization based password authentication

After looking at this security issue at DjangoProject, I started to think in a password-based authentication that places the burden of PBKDF2 (or whatever is the hashing function) on the client. So I ...
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Jumblar: Using map locations as passwords

I had the idea of converting map locations into passwords. Basically Jumblar takes a hash of the user's location and stores this as a comment on the PGP network. The 'stored-hash'(Vague-Hash) ...
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Which version(s) of SRP are in ISO/IEC 11770-4:2006?

I am on the impression that SRP emerges as the least uncommon and best analyzed protocol for authentication and key agreement based on a short password. This states that SRP is part of IEC 11770-4, ...
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Why does the SRP6 calculation of B included a multiplier k = 3?

In SRP6 $B$ is calculated as $B=kv+ g^b, k=3$. What is the purpose of $k$, and why was it fixed as $3$? (In SRP 6b, this value $3$ is replaced by $k = H(N,g)$, but this question is about SRP 6.)
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Academic papers on GPU password cracking? [closed]

Are there any scientific papers or publications on GPU password cracking?
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john the ripper, usages [closed]

As evident from the site of john the ripper, JTR example, john can be used for finding password form a unix machine passwd file. can JtR be used to crack password ...
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How exactly would someone crack a private key passphrase? [closed]

Lets say for a PGP/GPG pair with a passphrase.
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102 views

What can a master password also be called?

When having a company computer that is full disk encrypted, it is common that the boss have a master password / backdoor, so the data always can be decrypted. I have heard some call this for "scrow" ...
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1answer
126 views

How can encryption software accept password lengths which are not one of the AES key lengths?

AES comes with key sizes of 128, 192, and 256 bit. But in Truecrypt or other crypto software we can use passwords of different length, even less than 128 bit or more than 256 bit. How is this ...
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Where can I learn basic cryptography to know more about passwords and Bitcoin?

Basically my knowledge in passwords consist of setting up a Diceware master password back then, and I know hashes are not convertible back to the original password. Some basic question I want to know ...
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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 ...
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1answer
151 views

Strange Password Hashing

I know about PBKDF2, bcrypt, scrypt, etc. and while I'm not a crypt professional, I think I understand why are they better than just "hash(pass+salt)". But a colleague of mine surprised me with the ...
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Splitting a password for dual roles [duplicate]

I would like to prompt users for a single passphrase to establish trust with separate, normally (but not always) complementary systems from one password input. I'm essentially looking for a box where ...
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136 views

Securely generating passwords based on a secret and a public identifier

I'm trying to create a good scheme for generating passwords in my systems management scripts. What I'd like to do is have a secret key (let's say hello123), which I ...
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165 views

Password verification

I'm looking for feedback on whether or not this is the proper way to approach password verification without transmitting the actual password. Are there any problems with this scheme. We are working ...