Questions tagged [sha-256]
SHA-256 is part of the SHA-2 family of hash functions with a 256-bit output and a 128-bit security level.
603
questions
5
votes
5
answers
1k
views
Which hash algorithms support binary input of arbitrary bit length?
Background
In theory, hash functions produce a binary number having bounded (often fixed) length from binary data of arbitrary length.
In practice, specifications and implementations constrain the ...
- 151
0
votes
0
answers
24
views
SSL certificate fingerprint mismatch between OPNsense and browser
I've configured an OPNsense firewall's web GUI to use a self-signed certificate with the following SHA-256 fingerprint
However, when I open the web GUI from a web browser, it is showing a different ...
- 101
2
votes
2
answers
144
views
Is the quality of hash function essential in HKDF?
Hash functions have a number of properties needed, including the property that no collisions must be able to be found. Generally, if we can find collisions for hash functions, we consider the hash ...
- 1,613
0
votes
0
answers
66
views
Is sha256 quantum secure? [duplicate]
I've been reading about the security implications of quantum computing on cryptographic algorithms and came across some discussions regarding SHA-256. I understand that SHA-256 is currently considered ...
1
vote
2
answers
592
views
Sha256: Any significance in being able to find message schedules that lead from different initial hash values but produce the same hash?
Is there any significance in being able to find message schedules that result in the same hash but require different initial hash values? Can generate every 5-10~ minutes for any hash.
Confirmed ...
- 19
1
vote
0
answers
60
views
Why are Functions within sha-256 picked with certain exact magic numbers?
SHA-256, as described in its original paper, contains certain specific functions such as Σ1(X) = RotR(X, 2) ⊕ RotR(X, 13) ⊕ RotR(X, 22)
or ...
- 11
2
votes
1
answer
111
views
Rationale for the choice and majority functions of SHA-2
I've been trying to learn why the different stages to the SHA-2 family of algorithms were added - SHA-256 in particular.
Here's the pseudocode for the message schedule:
...
- 123
0
votes
0
answers
31
views
i want to verify the following p2pkh transaction
I know to veify the p2pkh transaction we have to place the unlocking script and locking script in a stack and than evalute the stack. In such cases the the scriptpubkey_asm is of the form <OP_DUP ...
- 1
1
vote
1
answer
137
views
What is the purpose of making salted passwords public?
So I was reading through an article about how passwords are salted and hashed through a cryptographic function here, and found out that hashed passwords, along with the plaintext salt values are ...
- 111
0
votes
0
answers
42
views
Is it possible to limit possible inputs of a SHA256 output
my question is as in the title.
For example, there are 2^256 different values that a SHA256 code can take.
But is it possible to shorten this number somehow?
4
votes
2
answers
4k
views
What’s the smallest known sha256 hash that was ever produced?
Basically the same question as this one, except in my case the value to be hashed doesn’t have to be a valid Bitcoin block, but is a bytearray of arbitrary length and content (and that my use case is ...
- 240
0
votes
0
answers
62
views
Multiparty Computation of SHA-256
I'd like to find a mechanism to evaluate the SHA-256 compression function using multi-party computation, but I'm not sure what's possible given the current state of the art and would appreciate some ...
- 642
14
votes
5
answers
9k
views
Boss insists on storing SHA2(p) || SHA3(p), claiming it "doubles security"
My friend in the software industry came to me with one of his "dumb boss" war stories. This particular time, his (non-technical but eager to learn) manager came to him and told him to, in ...
- 143
2
votes
1
answer
69
views
Rationale for BLAKE2 message schedule?
BLAKE2 uses a message schedule I did not see before. It uses permutations of pieces of the message block.
The BLAKE2 book did not state the rationale for such a choice and how it contrasts with the ...
- 224
3
votes
2
answers
810
views
How much entropy is lost due to collision?
If entropy is hashed with SHA-256 for example, and the input has exactly 256 entropy bits, how much entropy is reduced after hashing due to collision? Is there any reference that explains how to ...
0
votes
1
answer
886
views
How do bad actors manipulate game results in real time within 'provably fair' gaming systems?
Ive been assigned research involving online gaming companies and their use of cryptographic algorithms to produce 'provably fair' results. The largest player in the industry uses a method involving a ...
1
vote
2
answers
2k
views
Why is SHA256 used as a layer on top of Digital Signature [duplicate]
Digital Signatures use an asymmetric algorithm, meaning that if I want to apply a digital signature to a document I sign it with my own private key and send it to the recipient.
The recipient, thanks ...
- 129
1
vote
1
answer
250
views
Is the sha256 x86 extension close to optimal in silicon? (as it relates to a VDF)
I came across the Solana network utilizing sha256 as a "proof of history". They are using it as a pseudo-VDF (verifiable delay function). The reason it's pseudo is because verification is ...
- 224
1
vote
2
answers
4k
views
How weak is using AES with a 128 bit key but 64 bits of the secret key are public constants?
Respected community,
I was wondering how weak would AES-128 be, if we provide only a 64 bit key with the other remaining 64 bits either zero bits or public constants, known to the attacker.
Is it easy ...
- 1,060
0
votes
1
answer
377
views
Why hash algorithms have many different digest size variants?
1- Why SHA2 has SHA224, SHA256, SHA384 and SHA512 variants?
2- Can we say SHA512 more secure than SHA256?
3- Symmetric ciphers use at most 2^256 security level and I saw on the internet people saying ...
user111059
1
vote
0
answers
106
views
Zero Knowledge Proof for SHA-256 preimages [duplicate]
I need to design some protocol where actors will leverage Zero Knowledge Proofs (ZKP) to prove that they know the pre-image of some specific SHA256 hash without revealing the pre-image itself.
Ideally,...
1
vote
0
answers
273
views
Is it better to use PBKDF2 with SHA-512 and 1e6 iterations or SHA-256 and 6e6 iterations?
I'm implementing encryption in my browser extension that will allow users to encrypt their data and then share them with others. And since shared links can be leaked, I want to protect the data as ...
- 111
0
votes
0
answers
272
views
HMAC-SHA256 key length against key recovery attack
I have trouble finding information on the security strength of HMAC-SHA256 against key recovery attacks with respect to the key size.
To fit a certain application I must use a 128-bits key with a HMAC-...
1
vote
2
answers
44
views
Let $X$ be the set of 256-bit strings and $x \rightarrow H(x)$ a map on this set, where $H$ is SHA-256. How often is $H^-1(y)$ empty?
It cannot be "frequent" because that implies $H$ is not really 256-bit. Are there statistical or mathematical bounds on this? Finding the inverse is computationally difficult, but what ...
- 111
2
votes
1
answer
1k
views
HMAC SHA256 walkthrough examples
I'm trying to implement HMAC SHA256 (I've implemented SHA256 successfully).
I am trying to find examples where they show the results after each HMAC stage (XOR, append, H etc).
Does anyone know of any ...
- 123
-2
votes
1
answer
118
views
What is the critical importance of SHA and other hash families? [closed]
Assume integer factoring, discrete log are classical safe and LWE, McEliece etc are quantum safe. This question is only about SHA and hash families in general on why we need them if we have pkc ...
- 972
1
vote
0
answers
124
views
Inconsistent SHA256 checksums [closed]
I encounter an odd issue when I calculate SHA256 checksums in Javascript. I use the following code:
...
- 111
2
votes
1
answer
344
views
Implementing a Merkle tree using a 128 bit hash function?
I need to implement a Merkle tree using a 128 bit hash function. In general, any hash function that guarantees pre-image, second pre-image and collission resistance should be fine to implement a ...
- 149
2
votes
1
answer
1k
views
When using AES-256 in combination with HMAC-SHA, should we use SHA-256 or SHA-512?
When using AES-256 (cipher mode CBC and padding mode PKCS7) in combination with HMAC-SHA for authenticated encryption (assuming alternatives like TLS and AES-GCM cannot be used),
should we use SHA-...
1
vote
1
answer
2k
views
What does the 256 in SHA3-256 and SHAKE256 refer to?
I am simply wondering what the bit-length in the algorithm variant in the table below refers to? For the hash functions I assume that this refers to the ouput length in bits. For instance for SHA3-256 ...
- 335
1
vote
1
answer
152
views
Collision Resistance in Random Bit Generator
Consider following simple RBG where SHA-256 of random noise (more than 200Bytes of 4 bits entropy per byte) is computed to produce 256 output bits
$\text{output} = \operatorname{SHA-256}(\text{...
- 2,492
5
votes
2
answers
2k
views
Is there a way to calculate a hash with two people so that no one knows the pre-image but if they get together they do?
I'm trying to find a way to have multi party hash computation, more specifically for SHA256. I want for two people to be able to compute a hash so that none of them knows the pre-image but when they ...
- 140
1
vote
0
answers
380
views
Is my TypeScript scrypt implementation using Web Crypto API safe and correct? (Open Source)
I want to use TweetNaCl.js for encrypting user data that is stored in LocalStorage. Therefore, I want to prompt the user to provide a PIN/password that shall be ...
- 111
1
vote
0
answers
49
views
Verifying ECDSA-SHA256 HTTP Signature [duplicate]
With PHP, I'm trying to setup a HTTP signature verification for webhook requests coming from BlockCypher: https://www.blockcypher.com/dev/bitcoin/?php#webhook-signing
This is their public key: ...
- 33
2
votes
1
answer
2k
views
is this how RS256 works in JWT?
I'm a newbie that is studying about JWT using RS256 algorithm for signing and verification. I have drawn a diagram that represents my understanding of how RS256 works.
Basically, below is what I ...
- 121
3
votes
2
answers
752
views
is SHA512 with 256 bit set is similar or same as SHA256?
I'm new in Cryptography, if i will use SHA512, but only with 256 bits, is it equal or similar to SHA256?
I'm trying to understand if there is a way to use SHA512 as SHA256
- 31
0
votes
1
answer
96
views
Correlation between IV value and the output of a hash function
As we know, the IV and the output of SHA-256 are identical in size. Suppose the input value to the SHA-256 is completely transparent. Is there any correlation between IV value and output? Is it ...
- 175
1
vote
1
answer
384
views
How do most implementations of SHA-256 work?
Why is it that most implementations define an sha256_init, sha256_update, and sha256_final ...
user105744
8
votes
1
answer
221
views
AES vs. SHA2 in key-stream generation
A KDF in Counter Mode (e.g., see NIST SP 800-108r1, Section 4.1, similar to HKDF) produces the output as what AES-CTR would do if one replaces AES with SHA2 (or, to be exact, with HMAC).
However, NIST,...
- 138
3
votes
1
answer
1k
views
Why does SHA-256 have any to do with scrypt?
I was reading the Wikipedia page for scrypt because I wanted to learn more about it and I came across their pseudocode for the algorithm. What confused me was the following line:
I don't understand ...
- 300
1
vote
1
answer
159
views
Is there any point in extending an 80-bit key before using it for HMAC-SHA256?
I have been asked to make a HMAC-SHA256 password digest from:
a password
some salt, and
an 80-bit secret key.
I've been advised that I should be using a key of 256 bits or more for HMAC-256.
The key ...
- 948
3
votes
2
answers
1k
views
Password Hashing based on Common Passwords
If an attacker has a database of 1,000 users' hashed passwords which are hashed with SHA-256 with a 128-bit salt and all of these users used 10,000 common passwords. How many hashes will the hacker ...
- 161
1
vote
0
answers
449
views
What is more secure, HMAC with SHA-1, or with SHA-256 and take a substring?
I'm going to guess the latter, but just wanted to ask here.
I want to have a relatively short signature, and my goal is to take a substring of the resulting hash.
5
votes
1
answer
727
views
How can a preimage attack on SHA-256 always succeed within 2^256 evaluations when done though brute force?
I was reading the Wikipedia page for SHA-256 (SHA-2) and came across the following statement:
For a hash function for which $L$ is the number of bits in the message digest, finding a message that ...
- 300
1
vote
1
answer
134
views
Mod operation while verifying an ECDSA signature with SECT233R1
I'm trying to perform ECDSA verification in hardware. I'm using the SECT233R1 curve (NIST B-233). I have a question about the hash function used while doing so.
I want to use the SHA256 hash function ...
2
votes
1
answer
343
views
Generic attack on Hmac sha256
Is there any generic attack on HMAC SHA 256 ?
I am currently reading up on attacks on Hmac sha-256. However most of the papers I've found are about side channel attacks such as Differential power ...
- 33
4
votes
2
answers
2k
views
Password hashing and salting with SHA-256 on $2^{64}$ password space
If a password is randomly chosen from a space of $2^{64}$ passwords and is stored as an SHA-256-bit hash and a 128-bit salt, how many hashes does an attacker need to perform to recover the password in ...
- 161
1
vote
1
answer
655
views
Which hash functions provide 128 bit resistance?
I was wondering out of the functions (MD5, SHA-1, SHA-256, and SHA-512), do all provide 128-bit pre-image resistance and 128-bit second-image resistance?
Also, out of these hash functions, do only SHA-...
- 161
2
votes
1
answer
2k
views
How long does it take to decrypt AES encrypted message with salt(for pbkdf2 key) and iv known
I'm new to crypto!
The situation is,
Aes-256-cbc encrypted message(including not encrypted iv & salt) is revealed.
We also know pbkdf2 function uses 10000 rounds with sha256.
All we need to ...
- 135
-2
votes
1
answer
270
views
Does a pseudo-random number have the same security as its SHA digest message?
Is a random number generated by a CSRNG equivalently secure as the SHA hash of that number? I know that RNGs generate numbers that look random, and aren't necessarily random. For example, in a range ...
- 95