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.

learn more… | top users | synonyms (1)

2
votes
1answer
174 views

Security of re-encryption with a list of pre-computed password based keys

I have a problem where an encrypted file stored on a server needs to be decrypted through a precomputed list of passwords that are used one time only - OTP applied to encryption basically. The file is ...
2
votes
4answers
865 views

How password hashing is useful in MITM attack?

Even though I read a lot about hashing and how passwords are protected, I am still confused about it. If passwords are hashed at client side, it will be useless because it can be sniffed and used by ...
2
votes
3answers
689 views

Differences between brute forcing access versus decrypting password files or databases

I was just reading about how it's better to use bcrypt to protect passwords instead of saving password hashes in databases, and that got me thinking about other aspects that hackers work on that I had ...
2
votes
3answers
2k views

When to use the different types of Encryption / hash algorithm?

I'm studying for CISSP and know they will ask what type of encryption to use in different situations. Does such a list exist or is there a general rule of thumb to use?
2
votes
2answers
694 views

Time needed to generate an RSA signature of a document

How does the length of the RSA key and the size of the document affect the time it takes to sign a document using SHA-1 and RSA? I used CrypTool to check it, but the time does not appear to be larger ...
2
votes
1answer
64 views

Hashing algorithm for cryptsetup

I will encrypt my SSD using cryptsetup and I would like to know which hashing algprithm to use. First of all, cryptsetup benchmark: PBKDF2-sha256 262144 iterations per second PBKDF2-sha512 ...
2
votes
2answers
129 views

Reducing hash output length [duplicate]

I am using output of (keyed) hash function to make sure the input was not modified, I store it along with input. Now output of SHA-1 is 20 bytes. Say I want to reduce the output. And have it output 10 ...
2
votes
1answer
173 views

How can Alice and Bob prove that they share a file?

Carl asks Alice and Bob if they have a file f such that for a secure cryptographic hash function h, h(f) = K. Both claim to have f, but they can't show the file. Carl doesn't believe them. He can ...
2
votes
2answers
68 views

Virus - by-pass with binairies repackaging

Why don’t « hackers » (or more accurately, « virus maker ») just do repackaging over their malware to by-pass antivirus software? Because it resolves the issue of the virus signature (kind of hash), ...
2
votes
1answer
63 views

HMACs that have the same key and message

im using HMACSHA256 to generate the hash of password and store it. the objective here is to just authenticate users, i.e - save their hashed passwords, and validate users whenever needed using the ...
2
votes
1answer
553 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 ...
2
votes
1answer
120 views

Identical lanman hashes on AD accounts?

I ran metasploit's smart_hashdump module against my (2008r2) domain controllers, trying to find any accounts that may still have lanman hashes in place. These should have been disabled long ago. I'm ...
2
votes
1answer
266 views

PRF, IKE and hash function

The term PRF is mentioned in the documentation of the IKE (Internet Key Exchange) protocol. What is a PRF? What is the difference between a PRF and a hash function? What PRFs are used in the IKE ...
2
votes
1answer
159 views

How difficult it is to solve a salt if knowing the original data and the hash output that uses the SHA-2 algorithm

I am reading the documentation for Kentico where it describes using hashes to validate query strings ...
2
votes
3answers
750 views

Time Memory Trade-Off Attacks

Given, we want to crack a password. With Time Memory Trade-Off Attacks one tries to find the right balance between time to compute hashes for all possible passwords. And the used memory to store all ...
2
votes
2answers
234 views

Does sending two different hashes of the same password reduce security?

I'm updating a login system. The password is sent to the server as SHA512(password + long_string). I want to switch this to something like SHA512(username + password) in the future. By doing that I ...
2
votes
1answer
435 views

What key to use in HMAC

I need to use HMAC on a certain message to guarantee integrity, but I cannot figure out what are the requirements for the key to be given as input to the hashing algorithm. In particular I have to ...
2
votes
1answer
88 views

MITM vs. data leakage

We are designing a web API - accessible via https only - but two schools of thought seem to have arisen among our team: Group 1 wants to adopt an approach that is more concerned about data leakage ...
2
votes
1answer
948 views

How do I generate a blowfish password hash in Ubuntu?

What's the command line to generate a blowfish password hash? I can't seem to figure this out at all. Apache's htpasswd only supports bcrypt, and openssl passwd doesn't even do blowfish hahes (but it ...
2
votes
1answer
114 views

Securely store two values per user in SQL

I have come across the need in my web app to store two values for each user. These values would need to be retrievable from a value stored in a URL. I would prefer to store neither of the values in ...
2
votes
1answer
295 views

Legality and ethics of cryptanalysis on password hashes

I'm working on my dissertation concerning cryptanalysis on password hashes. I'd like to delve into the legal and ethical aspects of cryptanalysis, however, seeing as I'n not at all well versed in law ...
2
votes
1answer
97 views

What is the purpose of the hashcode used in Exchange OWA HTTP requests?

This blog describes the URLs that are used in OWA and webservices. It also says that there is a hashcode that is used in conjunction with the throttling policy. Is this hashcode responsible for ...
2
votes
3answers
1k views

Preventing dictionary attacks against hashed passwords [duplicate]

Possible Duplicate: How to securely hash passwords? I have a website and on that website I use SHA-256 and salt my user's passwords. What I'm doing right now is padding each letter of the ...
2
votes
1answer
69 views

What is a key-hardened hash?

I've seen the term 'key hardened hash' used to describe a recommended way to tighten up password hashing. What does this mean? Can it just mean to use a pepper?
2
votes
1answer
140 views

Why do major sites(Facebook, Google, etc) still send passwords unhashed? [duplicate]

QUICK SUMMARY: It seems like modern websites, for security's sake, should all have the client hash their own passwords before sending them to the server, who will rehash them, in order to avoid ...
2
votes
2answers
96 views

Randomness of hash token in password reset link [duplicate]

I want to know what are the points to be kept in mind while creating a hash token for my password reset links. In particular, how to make it un-predictable for an attacker?
2
votes
2answers
129 views

Difference between Second Pre-image Resistance and Collision Resistance in Cryptographic Hash Functions

I am studying the subject from these notes. However it is not clear what is the difference between "Second Pre-image Resistance" and "Collision Resistance" properties of Cryptographic Hash Functions. ...
2
votes
1answer
78 views

Security of shared “super pin” code table at meineschufa.de

The german brank credit report service "Schufa" uses a so called "SuperPIN" to enable users to reset their password. This super pin is a permutation of 30 lower and upper case letters and digits and ...
2
votes
1answer
242 views

HMAC secret key for securing communication - how to keep private on DB

I have a mobile app that communicates to server over HTTPS. To authenticate the client and to make sure its who I believe it is, I return upon successful signup (apart from the username) a secret API ...
2
votes
1answer
175 views

Is encrypting something more than once safer than hashing more than once?

I am aware of the implications that hashing something more than once correctly will increase the security of a system, but doing it incorrectly will decrease it, as noted here and on various other ...
2
votes
3answers
532 views

Tracking IP address to prevent abuse without logging user metadata

I am trying to balance good security practices against excessive logging of user metadata / Personally Identifiable Information. I am constructing a web app that allows for secure messaging. In part ...
2
votes
2answers
119 views

Breach informing

I am a staff member of a large fanfic site, but not the head administrator with control over the site itself. Recently, we had a security breach and the databases were copied, which included the ...
2
votes
1answer
420 views

FIPS 140-2 C# Password Hash

Is the following algorithm, using RNGCryptoServiceProvider & Rfc2898DeriveBytes, sufficient to implement a FIPS 140-2 password hash on Windows Server 2008R2? var provider = new ...
2
votes
2answers
241 views

Locality Sensitive Hash (LSH) function to approximately match old passwords

Recently, I ran across a website that requires me to change my password after X number of days had passed since I had last created one. Intelligently, the service made sure that the password did not ...
2
votes
1answer
64 views

Parameters in output of password hashing function

A number of encryption functions include their tuning parameters in the output. For example, SCrypt, which I've been considering for an app I'm building, outputs in the following format: ...
2
votes
1answer
943 views

sha-512 vs sha-3? [duplicate]

Does the new SHA-3 Keccak hashing algorithm offer any benefits from SHA-512? "Even worse, none of the SHA-3 candidates is significantly better. When SHA-3 is announced, I'm going to recommend that, ...
2
votes
1answer
693 views

Loki How to crack the password hash OSPF?

I have created for myself a lab of routers in GNS3 . Routing protocol between routers is OSPF. Now,by Loki penetration testing, I found that routers are the feature authentication. Using wireshark, I ...
2
votes
0answers
69 views

Is this symetric or asymetric encryption?

I’m at the beginning of my journey into the world of security. I am reading about the most fundamentals topics and I have encountered something unusual that has thrown me. The Conundrum: I have come ...
2
votes
0answers
31 views

How does SHA3 (Keccak & SHAKE) compare to SHA2? Should I use non-SHAKE parameters?

Keccak is the winner of the SHA3 competition. Since Keccak is highly customizable (presumably for security/memory/time/speed tradeoffs) there does seem to be some controversy around how Keccak ...
2
votes
0answers
51 views

Disallowing Similar Passwords [duplicate]

Upfront, I want to clarify that I am not a professional cryptographer, I am more curious about playing with the math and science behind it, and also want to improve my habits with my own personal and ...
2
votes
1answer
45 views

Authenticity of PDF document printed from Word

My MS Word Add-In generates PDF preview of DOCX file on client PC and uploads both files to server. I cannot generate PDF on server. Is there any way to make sure that the PDF is the printed version ...
2
votes
0answers
46 views

How secure is Visual host key, and how is SHA2 converted into that representation?

SHA2 has 256 bits of possibilities. Visual host key seems to have the following upper and lowercase = 26*2 numbers and symbols = 20 Additional symbols = 22 Total 94 characters represented in ...
2
votes
1answer
143 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 ...
2
votes
0answers
52 views

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 ...
2
votes
1answer
176 views

Stream/Block encryption using XOR and Hash function?

Could a hash function like sha1 or ripemd-160 be used for secure key generation in a stream/block cipher? Obviously a repeated key like "abc123abc123abc123" would be bad, and a one time key pad would ...
2
votes
1answer
306 views

ASIC/FPGA hardwares to compute Scrypt hashes [closed]

this company claim Scrypt mining by ASIC (on crypto currencies who use scrypt hashing as proof of work) scrypt is made to keep ASIC/FPGA attackers away, is that claim expired?
2
votes
1answer
380 views

Legality of downloading leaked hashes / attempt cracking [closed]

Note: I realize there is no legally binding talk hereinafter. There are lots of leaked password hashes on the internet. Twitter searches for "hash dump" pull back tons of links, generally from "deep ...
2
votes
0answers
345 views

How do I convert from this weird John/Asleap format to lc (for HashCat)?

I'm trying to setup a system for pen-testing. I'm using the FreeRadius-WPE patch to collect Challenges/Requests from people who connect to my spoofed AP instead of the actual network. Here is the ...
2
votes
1answer
1k views

How to save the random salt to the database

As I understand it, salting and hashing passwords is the way to go. I also understand that to authenticate a salted and hashed password, the random salt needs to be saved. Does this mean that if I use ...
2
votes
1answer
221 views

Seeding GPG keygen with a hashed secret [duplicate]

Possible Duplicate: Tool for public key cryptography where password is the private key? I was wondering if you guys could clue me in to potential problems with using a hashed password as ...