Passwords are secret keys which human beings can memorize.
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2answers
48 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 ...
0
votes
0answers
45 views
Password checking algorithm
I'm trying to reverse engineer key exchange protocol and faced with the following problem:
Protocol is based on Diffie-Hellman key exchange method:
g - generator
m - modulus
Alice:
a - private key
$A ...
-1
votes
1answer
80 views
Trying to finalize my understanding about password storing
am sorry, an a beginner, so please forgive me if i make mistakes, so here is what I understood:
PBKDF2: uses HMAC, so, the message is the password, and the key that crypts the message is the salt? or ...
1
vote
3answers
140 views
How Scrypt uses Salsa?
Bcrypt use Blowfish to crypt a derived key from the passphrase, Blowfish is a cryptographic algorithm, but here it is said that:
Note that
Salsa20/8 Core is not a cryptographic hash function ...
1
vote
1answer
115 views
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?
...
2
votes
0answers
40 views
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, ...
0
votes
1answer
96 views
Best way to create password manager [closed]
After some searching I wasn't able to find a password manager that fits me (able to sync from my own server, open-source, secure enough and browser auto complete). So, I thought that I will create ...
5
votes
4answers
404 views
Encrypt a file once with 50 characters password or twice with 25 characters?
What better Encrypt the file once with 50 characters password or encrypt it twice each time with 25 characters password.
4
votes
1answer
176 views
Using an MD5 hash as a password
Suppose Alice is using a password prompt that only accepts up to 32 characters for any particular password.
Memorization of long strings of random characters is not one of Alice's strengths, so she ...
2
votes
1answer
122 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 ...
1
vote
1answer
108 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 ...
0
votes
2answers
79 views
Using salted hash as password for easy memorization without reuse?
I had an idea earlier:
Secure passwords are a) long, and b) unpredictable. A hash is both of these. Would it be safe to reuse a key between sites, and include the site's name as a salt? For example:
...
2
votes
0answers
110 views
Single-purpose symmetric encryption scheme for single files
I'm writing a simple password manager program that will encrypt/decrypt a single file (it's size will most likely stay under a few K). This is my initial file format design:
...
1
vote
2answers
105 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 ...
2
votes
2answers
151 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 ...
4
votes
4answers
202 views
Could a very long password theoretically eliminate the need for a slow hash?
Before I provide details, I want to clarify that I am not looking to implement this practically, but I'm only asking to get a better understanding.
The way I currently understand it, we use slow ...
0
votes
1answer
95 views
Sensible usecase for restricting special characters in passwords? [closed]
Please See Why Not Allow Special Characters In a Password on Security.
Several websites I've come across limit the allowed special characters for a password. My thought was, it should all be ...
1
vote
2answers
170 views
Deriving HMAC key and cipher key from passphrase? [duplicate]
I'm encrypting a file with AES-256 in CBC mode. I needed to add an HMAC for authentication and validation of the file contents and passphrase, so I used a SHA-256 HMAC over chunks of my file ...
2
votes
0answers
72 views
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.)
5
votes
2answers
133 views
Can the hash of one message be used to make it easier to find the hash of a very similar message?
Background:
I am trying to get an understanding of using a hash of a passphrase as a secret.
Example:
...
2
votes
2answers
121 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 ...
1
vote
1answer
100 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 ...
2
votes
2answers
190 views
Hashing passwords with a salt - why use different salt for everyone?
Given a database where we have usernames and passwords, we want to secure users' passwords by hashing them. We should not use only username and passwords in this hash, as someone having data from ...
4
votes
3answers
216 views
Initialize a PRNG with a password
Let's assume that we have a secure PRNG. Is it "safe" to initialize it with password, or seed based on a password like SHA256(password).
If yes, is it "safe" to generate as RSA or DSA key from it? If ...
4
votes
1answer
91 views
How to generate a key using any m passwords out of total n?
My application requires an AES-256 key K for some secure operation. In order to avoid saving this key in application, I have implemented following scheme:
There ...
2
votes
0answers
46 views
Encrypting or HMACing password digests
Assuming I'm using bcrypt to digest passwords, is any additional security gained by either encrypting or HMACing the resulting digests? By requiring a key to compare password hashes, I would expect ...
2
votes
1answer
175 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 ...
1
vote
2answers
111 views
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 ...
3
votes
2answers
174 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 ...
2
votes
1answer
162 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 ...
3
votes
1answer
210 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 ...
3
votes
1answer
182 views
Exhausting the entropy of a hash function
In the case of password storage, consider the following:
I have an idea that one can exhaust the entropy of input to the MD5 function by using a 128 bit random value as the password (indeed, any hash ...
1
vote
2answers
81 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" ...
-1
votes
1answer
93 views
Pseudo-random Number generation for Passwords
i want to know what is the best pseudo-random number generation algorithm for passwords? for example my scenario is I have to generate 5K pseudo-random bits from a user-supplied password(6 ...
2
votes
1answer
115 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. ...
0
votes
1answer
176 views
password entropy calculation
I have the following password with a prescribed format: it starts with a fixed value of 111, followed by 2 random lower case letters and then lastly a random digit:
"111""2 Random lowercase ...
2
votes
1answer
203 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?
4
votes
4answers
216 views
How is it possible to parallelize a hashing function to crack an iteratively hashed password?
Suppose I have an algorithm that relies on multiple iterations of a hash function like SHA1 to slow down an attacker trying to bruteforce a hash.
...
5
votes
3answers
174 views
Stretching passwords for encrypting small files
I would like to know how to store a sensitive file; a credential of sorts. I want to password-protect it, obviously. It would be appropriate - in my application - to prompt the user for the password ...
0
votes
0answers
118 views
Password crackers in CUDA [closed]
Is there any good password crackers in CUDA. Is the version available free of John the ripper can be deployed in CUDA?
8
votes
2answers
362 views
Do I have to have a different salt for each password?
Should I use a different salt for each password?
In my system, there are no user names, only passwords. When a user logins in, he types in one or more passwords and the server compares the results ...
4
votes
2answers
798 views
Is there a way to make RC4 (ARCFOUR) secure, or is it completely broken?
I need a method to authenticate a process with another in order to establish interprocess communication between them, to prevent malicious processes from trying to hook onto the system. Currently I ...
2
votes
1answer
1k views
How do I store encrypted files on a web server and decrypt them locally?
I want to store files (images) on a public webserver and let users see them if they know a password. The server shouldn't have the unecrypted files and the server can only serve files, not perform ...
5
votes
1answer
223 views
Why does SRP-6a use k = H(N, g) instead of the k = 3 in SRP-6?
I've been reading up on the Secure Remote Pasword protocol (SRP). There are a couple different versions of the protocol (the original published version being designated SRP-3, with two subsequent ...
4
votes
2answers
192 views
Do MD5's weaknesses affect Oplop?
Oplop is an algorithm that generates account-specific passwords from a master password and user-chosen nickname (typically username@domain). From the website:
Concatenate the master password with ...
0
votes
2answers
132 views
Is stretching hash several times basically the same as bcrypt?
As I understand it, the main advantage of bcrypt is stretching so it becomes slower to crack overtime. But, is using a "good enough" algorithm (e.g., SHA-2 family) then stretching until it's slow ...
5
votes
2answers
188 views
Can I use a key-derivation-function as the hash function H in SRP?
In the Secure Remote Password Protocol, the verifier must be stored on the server. In the case of a server compromise, an attacker could obtain these verifiers. If nobody reused passwords, this ...
2
votes
2answers
180 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 ...
3
votes
2answers
145 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 ...
6
votes
2answers
350 views
Is bcrypt better than GnupPG's iterated+salted hashing method?
GnuPG has slow hash built-in in form of iterated+salted S2K.
Does it have disadvantages in comparance with bcrypt or scrypt? Is GnuPG's slow hash method easily automated in GPUs?
