A hash algorithm is a function which takes a variable size input and produces a fixed size output. The algorithm tries to make it difficult to predict the output for a given input, find two inputs with the same output, or reconstruct the input from the output.

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Digital signatures and weak hash functions

There was this question in last year's exam. The teacher claims that answer b) (in boldface below) is correct. Attacks are constantly being performed on digital signatures which use weak hash ...
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How to compare passwords with duplicate password

On Steam, the gaming client, I have this habit of creating multiple "smurf" accounts. I have a randomly-generated, unique password, and I decided to use the same password for all of my multiple ...
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55 views

RESTful web application security and authentication scheme

I am building a web application where the front-end is a single-page-app and the back-end serves it through a RESTful API. I want to make sure I implement user authentication with the best security ...
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37 views

Crackstation “Secure Salted Password” Java example - is it really secure?

I'm making an auth service so I've been looking for some good Java/Groovy implementations of password + salt hashing. I've found this article on crackstation along with a code example and decided to ...
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What is the best way to transmit password hash over unreliable TLS?

I have TLS connection between my server and client. I have no certificate, so the connection is susceptible to the Man-in-the-middle attack. I fear that attacker could intercept the password hash ...
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114 views

Generating authentication token from PHP sessions

I have a traditional PHP site which uses sessions. I've developed a real-time app in nodejs and wish to authenticate users here based on their PHP session. The procedure would go something like this: ...
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How can I set the SHA digest size in java.security.MessageDigest? [migrated]

I am kinda playing with the SHA-1 algorithm. I want to find out differences and variations in the results if I change few values in the SHA-1 algorithm for a college report. I have found a piece of ...
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3answers
92 views

How can I create a unique identifier that can not easily be reversed?

I've been working on the design of a longitudinal study and one requirement is: all participants will have a unique identifier that is not reversible from the data storage/analyst side of the study ...
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2answers
69 views

How to transform an hash into a usable password?

I was reading about PwdHash and it inspired me to create a little project where you input a master password and an easy to remember alias into a password hash, like bcrypt, and then you get an hash. ...
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46 views

Is authenticating via the database secure

Sorry for this probably noobish question. So far, I've read password comparison/verification is implicitly understood to be made on the application layer and not in the database. For example in PHP, ...
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How is hashing safe if a given string always generates the same hash? [duplicate]

I am a newbie to hashing, and I understand that MD5 (I know it's broken) and SHA-1 are all fixed hashing algorithms, but given that most passwords are dictionary words or other similar passwords, ...
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1answer
77 views

TrueCrypts full Disk Encryption still secure? [duplicate]

I'm wondering because it only uses RIMPEMD-160 with just 3000 iterations. Isn't that somewhat low and weak? Even though I saw the NSA document that the NSA were not able to break TrueCrypt in 2012.
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Brute Forcing LUKS Full Disk Encryption - Time?

let's say we have encrypted our drive with AES 256 XTS and the following Hash: SHA1 with ~500k Iterations and a 20+ password SHA512 with ~250k Iterations and the same 20+ password. Let's think of ...
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74 views

About SHA1 in default Disk Encryption in Linux

Link to the Thread: Recommended options for LUKS (cryptsetup) I wonder what's the exact difference between SHA1 and SHA512. I know that SHA512 has a longer key but I've read that it doesn't matter ...
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5 views

What kind of attack does the current brokenness of SHA-1 allow? [migrated]

I understand that the following is becoming feasible, or already is: Find any 2 data (d1 and d2), for which SHA1(d1) = SHA1(d2) However, it is not entirely clear to me if there is evidence of the ...
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242 views

Are all unsalted password hashes inherently insecure?

Maybe I'm missing something obvious... Are all passwords stored in common, unsalted hash algorithms able to be attacked via rainbow tables?
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31 views

PBKDF2 strong salt for client-side hashing

What should I use as a secure/strong salt for PBKDF2 hashing when salt is not available to use before login as it will be client-side javascript to hash user+pass with PBKDF2 ? I'm going to use ...
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26 views

PBKDF2 strong salt

I want to use a strong authentication scheme, so I decided to use PBKDF2. I'm using PBKDF2 with SHA256 algorithm, 5000 iterations and I use username (which is full email address of user) as salt. So ...
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176 views

Testing a password for similarity to previous hashes

This question is a follow-up to a comment by Tobias Kienzler to an answer to "What is the purpose of the “Password minimum age” setting?". Consider a password policy that new passwords cannot be ...
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Any problems with scrypt yet?

In the question Do any security experts recommend bcrypt for password storage? Thomas Pornin recommends the hashing function scrypt but saying it is "too new to be recommended on a general basis". ...
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Are credit card number look ups more secure with a hash function than with a deterministic encryption algorithm?

I understand PCI DSS 3.0 allows hashes of cardnumbers to be stored separately from encrypted values, but I'm startled at the efficiency of tools like hashcat in discovering card numbers from hashed ...
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which memory hard hashing algorithm can equalize low-computational and high-computational power devices to utilize blockchain in the IoT?

Recently IBM and Microsoft showed their interest (IBM post, Microsoft post) in utilizing bitcoin's blockchain for internet of things (IoT) development. Let's assume that in close future the blockchain ...
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Storing salt and hashed password [duplicate]

Is there a benefit to storing salt appended to hashed password in a single column of a table verses storing salt and hashed password in different columns of the table. The OWASP guide here ...
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71 views

How much risk is introduced by git's signing the commit hash rather than the blobs? [duplicate]

Since first switching from centralized VCS systems to a decentralized one—specifically git—I have properly understood that that git's commit ID's were hashes of the included objects and some meta data ...
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25 views

How to secure sensitive data in application with message queue

Currently we are creating one small service, where we are using some sensitive data from users(not worth zillions but to me it is like password). The idea is that application itself only inserts this ...
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Can I prevent brute forcing of hashed+salted user passwords without a dedicated validation server? [duplicate]

Salted hashes don't seem to offer any real protection for user passwords by itself. So long as a hacker has a quick way to check if a password is right or wrong, it's trivial to brute force it to view ...
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One-way function for data synchronisation

I have to synchronise small sets of data between two or more systems over an insecure network. First I have to check that the other system has the same unique identification information for the data ...
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How can I find out the password hashing schemes used by the specific Unix accounts I log in to?

Every day I ssh in to 3 or 4 independent Unix accounts. I have been regarding them as more or less "equivalently secure" on the grounds that I'm using ssh, but after learning of how much variety ...
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67 views

Is it safe to use a derivative of a password as a salt

I know for a fact that salts are an important part of storing a password securely in a database. Most people store the password hash, and the salt that was used for it. This, I have learned, isn't ...
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112 views

Which PHP encryption method is most incidentally-secure?

just started researching on the latest PHP encryption methods, I've found out my favorite algorithms are compromised. MD5 is no good, SHA-1 has "found flaws", SHA-512 isn't "meant for passwords", ...
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2answers
106 views

John the Ripper not identifying a password contained in the username?

I have uploaded a screenshot of what exactly is going on, here: http://i.imgur.com/bJSv7C8.png I can see that single-crack mode includes a rule that looks at the username, and "slices" it to identify ...
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1answer
170 views

Good password hashing algorithm compatible with PHP and Linux apps

I'm looking for a password hash method for a new server system. The hashes must be generated from PHP code and verified from PHP as well as by a number of applications on a Linux system. I know that ...
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Is it possible to pass the hash with a hash captured from spoofing NBNS responses?

I know that it is possible to use a hash obtained from the Windows SAM in a pass the hash attack, simply setting the hash for the SMBPass paramter for various modules in metasploit. Can a hash ...
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Identifying hash format caputred via Metasploit

When I use the nbns_repsonde module in metasploit, and set it to write captured responses to a file in the john format, I get a file with lines such as this: ...
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A secure way to encrypt a connection between 2 clients securing against both passive and active adversaries

Recently I got interested in encryption and the methods behind them. So for a fun / school project I am building a program in python to encrypt data between two clients (chat and files). I'm just ...
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52 views

PHP: Save e-mail address hashed or plain [duplicate]

I've been wondering about something, is it more secure to store an encrypted (hashed with password_hash) email address in the database, or just as plain text? I've google'd this matter and saw that ...
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1answer
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Please help clarify password hashing - salted, multiple iterations of MD5 vs bcrypt/sha2, etc [duplicate]

I was reading an article about the Ars Technica hack here and had a couple of questions. The commenter said: "PHPass uses salted and iterated MD5 to hash passwords" My question is that if I were ...
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68 views

Separate database column for salt

Is it advisable to store the salt in a separate database column or should we concatenate it together with the password? Is there any difference? I have come across implementations of both types. ...
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64 views

What's the best way to transform sensitive account numbers

I work on a web application that manages information about transmission setups and processes client transmission statistics to generate billing charges for the services used by these clients. The team ...
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432 views

Torrent “bad seed” attack by Sony, how does it work?

Sony recently saw a large amount of data stolen. In order to prevent the stolen data from being spread using torrents, they are doing what was called a bad seed attack. What is this attack? Is this a ...
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173 views

Reverse Engineer this basic Hash using known answer?

Little background: I forgot one of my CCTV accounts password, so used the admin account to create a new one. However I can't access the old one as it's not possible to change a user account password, ...
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HMAC-SHA256 Transaction signing [closed]

Can rfc6238 be used for transaction signing by concatenating the random seed string with transaction details (such as amount and target account number) ? Could a transaction authorization 8-cipher OTP ...
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Passing the hash with metasploit and psexec not working - why? [closed]

I am currently doing a penetratiion test, and have captured a bunch of NTLM hashes via NBSN spoofing. An example (this is not taken from what I captured, and is random but the format is the same) ...
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2answers
413 views

PBKDF2: can the salt be known from the hash?

I understand that some KDFs bundle the salt with the output, such as bcrypt (modular crypt format). In PKCS5_PBKDF2_HMAC (specifically, looking at OpenSSL implementation) with a single iteration, is ...
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1answer
57 views

Verify CDN javascript's integrity

CDNs speed up the loading of websites by allowing caching for frequently used javascript libraries like jquery. How do we know if they have modified the javascript before serving it to my clients? ...
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1answer
53 views

find out the algorithm based on some examples?

I have an OTP generator that receive two numbers less than 99 as input and return an 8 digit number as its output. I know it has a simple algorithm. because its processor is just an ATMEGA8 micro ...
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219 views

TrueCrypt VS LUKS Bruteforce Resilience

I have been researching LUKS vs TrueCrypt topics -- my only concern is security, but most of the discussions I see focus around usability / interoperability . I know TrueCrypt has a bunch of nice ...
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59 views

Why not use md5 auth mechanisms for IMAP over TLS?

I'm using Dovecot for IMAP connections. I've read a lot of tutorials on how to set up Dovecot, and a lot of them said to only allow: auth_mechanisms = plain login Why should I not allow *-md5 ...
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Do I have to hash users' IP addresses when I log them?

I have read a lot of users saying that you have to hash IP addresses - and a lot of others who say I don't have to because it is not private information. I use IP addresses for identifying users, ...
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3answers
145 views

Are there any flaws in this two way cryptographic function?

I created a simple two way cryptographic function which allows you to encrypt a message and decrypt it with the same key. Here's how it works. Split the message into an array of 32-bit (or something ...