Tagged Questions

A cryptographic hash algorithm is a function which takes a variable size input and produces a fixed size output. The algorithm makes 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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Rainbow Table - Number of Chains and Chain Length

Is there a difference between having 10,000 of chains (with 1,000 chain length) and 10,000 chain length (with 1,000 of chains)? How does it affect the success rate of the rainbow table? I understand ...
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Large Volumes of Asymmetric Encryption

First of all, I apologize in advance if I use any incorrect terminology. I am just getting my feet wet when it comes to cryptography and there is a lot to learn. For the past 12 months we have been ...
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What may be causing conflicts in Whirlpool implementation versions?

I see by layman articles (e.g. at Wikipedia) that the Whirlpool hash function has seemingly three current versions. That is to say, they are referenced as ...
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I'll define an example hash-based stream cipher as such: $H: \{0,1\}^* \rightarrow \{0,1\}^{256}$ is the hash function. $K=\{0,1\}^{256}$ is the secret key. $N=\{0,1\}^{128}$ is the nonce. $C=\{0,1\}... 1answer 55 views can anyone explain inversion per byte? I am designing the truncating block of SHA3 algorithm , there its given that first we need to do the inversion per byte of the 1600 bit output and then truncating it to give 512 bits output. Can any ... 0answers 24 views Filling in MD5 input variables I have a majority of an input string(as well as the total length) and the output for an MD5 hash. Is there a way to calculate the remaining input bytes that I am missing? 1answer 116 views Calculation of the avalanche effect coefficient Given a strict avalanche criterion matrix/dependence matrix for a hash function,how do I calculate the avalanche coefficient for it. I want to calculate a single parameter(value) which represents the ... 1answer 50 views What are fixed points and length extension attack in hash functions? I was recently reading about hash functions, and I came across fixed points (one or more fixed points, interested in both) and length extensions, but I didn't exactly understand how these work. If ... 1answer 273 views Non-iterative cryptographic hash functions Consider the following cryptographic hash function$H$which maps a message$m$of variable size to$b$bits: $$H:\{0,1\}^{*} \mapsto \{0,1\}^b$$ $$y = H(m) = SPRP(IV||m||padding)\mid_{b}$$ , where: ... 1answer 29 views Partial-Message Collisions on Iterated Hash Functions In Cryptography Engineering by Ferguson et al it says the following is a problem with iterated hash functions: Because hashing$m$and$m'$leads to the same value,$h(m||X) = h(m'||X)$... for all ... 1answer 277 views What's the safest TrueCrypt algorithm and hash? I have an encrypted file container inside my NTFS pendrive. The root folder Write permission is blocked for everyone. A folder inside it has all permissions unblocked. The dummy file of TrueCrypt is ... 1answer 55 views Collision-Resistance Hash Function PRF I am trying to solve the following question with an example/proof. The question is from Introduction to Modern Cryptography by Katz and Lindell. Any help would be appreciated. 1answer 81 views What are the applications of sha3 algorithm? [closed] I know it is used for digitally signing any data or message. It can be used for sending any message securely, but where is it applied in industries? Can anyone tell the practical applications of$\...
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I'm studying mechanisms of integrity and authentication in symmetric encryption scenarios. I want to propose some examples to see whether I got the point here: Let $m$ be the message, $c$ the ...
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How to invert a linear hash function?

My friend is trying to convince me that his linear hash function (with a few bit operations) is secure. Is there a way to disprove this? (Or prove this, but I've read from multiple sources that this ...
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Parallel hashing function that always gives the same hash despite a variable number of cpus

The title pretty much sums it up :) I'm looking for a hashing algorithm that does not need to be cryptographically secure beyond reducing the number of accidental collisions. There is no need to ...
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How to choose the reduction function in rainbow tables?

I have a question regarding Reduction Functions in Rainbow Tables. If the hashing function is MD5 or SHA-1 etc then should the reduction functions also be MD5 or SHA-1? That is, should the Reduction ...
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Reversing a hash of known hashing algorithm

I am sure this is a very easy thing to do but I am not sure how to go about solving a problem like this, So there is this hash function which operates on a message which is in the form of a byte array ...
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Given the first half of a SHA-1 hash, can you predict the second half?

I know this applies to secure ciphers, but does this also apply to hashes?
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Can the SHA256 hashes of consecutive integers be attacked?

Suppose that the attacker knows the SHA256 values of integers $n, n+1, n+2 ... n+k$. $n$ is sufficiently big, so we do not expect to be able to brute force $n$ just by $\operatorname{SHA256}(n)$ ...
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How is the message digest related to Signatures and Encryption?

I was studying about 'Data Security' and I found out this one thing confusing. What is an message digest? I got it is the hash of the message. Is the message here referring to the plaintext or ...
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I've noticed that SHA-512 password hashing leaks some information about the password length. There's a weak correlation between password length and time to hash. It's roughly linear, but in steps of ...
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Why is Pearson hash not used as a cryptographic hash?

The original algorithm produces 1 byte long hash and is (of course) not suitable for cryptography use. But according to wikipedia, it is possible and easy to produce Pearson hash of any length, ...
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Difference between MAC and Authenticated Encryption?

I am currently studying authenticated encryption and I was wondering if there was a difference between using a MAC and authenticated encryption. It seemed like authenticated encryption schemes use ...
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Weak and Strong Collision Resistance, again

Weak collision resistance (CR), or second-preimage resistance, is the property that given $x$ and $h(x)$ ($h$ a hash function) it's difficult to find $x' \neq x$ such that $h(x') = h(x)$. Strong CR, ...
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Negative lookup table concept

Interested in password cracking, I thought of a concept for lookup tables that can tell if a hash can be created using a dictionary in about O(log n) time. A simple overview of the idea is a follows: ...
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Create a potential input for sha-256 hash given a substring of input?

Let's say I'm given a specific SHA-256 hash. Further assume that the SHA-256 input, that yielded this hash contained a known sub-string. Is there a way to find the input (containing the specific ...
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PHP AES 256 CBC faster than AES 128 CBC? Or am I doing something wrong?

for last couple of days I'm learning a bit about encrypting data in PHP, as I need a good encryption/decryption function for storing user's passwords in DB. I use ...
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Is it ok to store the plaintext hash of encrypted data

Is it ok to create and store the hash (unkeyed hash function) of a plaintext before encryption or does it lead to vulnerabilities? If it is ok are there requirements for the used hash function and ...