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.
339
questions
82
votes
4answers
10k views
Has SHA256 been broken by Treadwell Stanton DuPont?
In a recent press release issued by Treadwell Stanton DuPont the claim is made that their research laboratories have successfully broken all 64 rounds of the SHA256 hashing algorithm. They further ...
0
votes
0answers
40 views
If I don't want to ever decrypt, is it secure to store SHA256 hashes of sensitive but unique values? [closed]
My plaintext values are guaranteed to be unique. Also, I am not interested in ever decrypting. In this case, can I use SHA-256 to store the hashes of my plaintext values securely?
0
votes
1answer
27 views
Is the AES-GCM encryption using the SHA256 hash of the plaintext as IV secure?
I want to encrypt a list of unique values and I want the property of when I encrypt the same value I get the same ciphertext (determinism). The adversary only observes the ciphertexts of a unique set ...
0
votes
1answer
59 views
Hash key expansion
A hash H is given by H = SHA256(K + N), where K is an unknown 64 character hex key and N is a known nonce.
The nonce N is then mapped to a final result R between 1 ...
2
votes
1answer
87 views
Using an AES-256-GCM key as a salt to SHA-256
Assume 256 bit keys are randomly generated and data is encrypted using AES-GCM-256 prior to being sent to a server.
The goal is to enable the server to determine uniqueness of data it receives ...
3
votes
2answers
110 views
Statistical Analysis of Cryptographic Hashing Algorithms
I was wondering how can I use NIST Statistical Test Suite to check for the randomness of output generated by a cryptographic hashing algorithm, let say SHA-256?
To be specific, how will I generate ...
2
votes
3answers
142 views
Use a SHA256 as a key for AES256
Is it safe to use the SHA256 of a hard-to-bruteforce string as the key to encrypt data with AES256?
3
votes
1answer
136 views
Circular hash collision where digest is pre-image: Could hash(a) = b, hash(b)=c, then hash(c)=a?
For any SHA-family of algorithms (including Keccak) except for SHA1, would it be theoretically possible for there to exist a pre-image a whose hash digest ...
1
vote
1answer
99 views
Is it possible to truncate AES output and keep uniqueness (no decryption needed)? [duplicate]
I would like to hash numbers less than 1000000000, so generally they could be stored on 30 bits. The aim is to obtain numbers that are not reversible, so my initial plan was to use SHA256 (with some ...
0
votes
1answer
61 views
Does every language's SHA256 implementation provide different result for the same value [duplicate]
Probably this is very naive question, based on lack of understanding but I was watching a video from Andreas M. Antonopoulos about blockchain, bitcoin and consensus algorithms and he asked for the SHA-...
0
votes
1answer
54 views
Bitcoin mining nonce and birthday attack
Having read the basics of mining and this about SHA256 (probabilistic?) partial preimage possible? and SAT solving - An alternative to brute force bitcoin mining, I have the following question:
...
1
vote
0answers
38 views
SHA256 creates a unique hash for two *.wim that have identical content - are there better methods for verifying *.wim contents? [closed]
I'm trying to verify that the contents of a Windows Image are identical for two WIM files; however, I think the timestamps for the file modifications are affecting the final checksums--even though the ...
5
votes
2answers
160 views
Collision resistance of partial SHA-256 hashes XOR'ed
My hashing algorithm computes the SHA-256 for each of 12 input strings and XORs them to get the final hash.
Is there a risk of an attacker being able to forge 2 sets of inputs that yield the same ...
0
votes
1answer
67 views
Do I still need SHA256 if I already had a AES 256 key that is 44 characters long?
Several months ago, I was required to research on AES and SHA-256 to make a secured license system for my app. However, I was dumb enough that couldn't distinguish between the 256 bits from AES and ...
-1
votes
3answers
222 views
SHA-256: One input, two different outputs?
I am new to SHA-256. I have discovered that the same input could produce different SHA-256 hash ouputs depending on the (online) device I chose for generating the hash.
Is this normal, or is there a ...
0
votes
1answer
53 views
How does sha-2 with fewer rounds work?
The wikipedia page about sha-2 states:
Currently, the best public attacks break preimage resistance for 52 out of 64 rounds of SHA-256 or 57 out of 80 rounds of SHA-512
How exactly is the sha-256 ...
3
votes
2answers
134 views
Hashing a hash for authentication
I currently use Argon2 to derive a key (I will use a salt which I will save in a file as plaintext for when I later need to derive a key again) from a given password which I will use to encrypt a file ...
2
votes
3answers
131 views
Suitable 16-bit checksum?
I am writing a toy1 transport protocol and I am trying to implement a feature whereby:
A 16-bit checksum is included in every packet.
This checksum can be extended to be 48-bit if the data is large, ...
-1
votes
1answer
47 views
Is it possible for a hash in SHA-256 to have more than 8 digits? [closed]
Is it ever possible for a hash to have more than 8 digits in SHA-256?
0
votes
0answers
62 views
Why initialize values and array SHA256 with specific buffer?
Why initialize values and array SHA256 with specific buffer?
...
0
votes
2answers
125 views
How is the hash for a file calculated?
Is the file just read bit by bit to calculate the hash with those values or is there more to it?
Are there any resources to read a bit more about file hashing?
1
vote
1answer
104 views
SHA256 message schedule examples
I need some example values for the message schedule stage of SHA256 to test this part of my implementation.
If possible in binary, for the string 'abc'.
0
votes
2answers
67 views
For the hash computation of SHA-256, is it computed in parallel or series?
I'm trying to write my own SHA-256 implementation in VHDL, which runs in parallel execution style
I have been using this as a reference to the SHA-256 algorithm: https://www.researchgate.net/file....
1
vote
1answer
66 views
ECDSA signature of a random 32 byte number vs. the hash of the number
I'm working on an application that involves signing a 32 byte random number generated by the OS. Assuming the RNG works as intended, is it safe to sign the random number itself rather than a hash of ...
0
votes
1answer
52 views
Bitcoin mining: how is a block header of 80 bytes processed in SHA-256? Isn't it too big?
The whole process of bitcoin mining was making sense to me until a moment of madness an hour ago, if there are 80 bytes of data to be processed in SHA-256, that's 640 bits of data to be processed in ...
2
votes
1answer
97 views
Use a hash-function twice
I'm creating a small messenger and I wanted to know if it makes sense to store user passwords double-hashed in our backend-database. I wanted the user the register in an app, which should save a hash ...
0
votes
1answer
99 views
Is there any Corelation between the SHA256 and SHA512 hash of the same data?
Is there any Corelation between the SHA256 and SHA512 hash of the same data ?
4
votes
2answers
3k views
What is the difference between SHA-3 and SHA-256?
I am new about cryptography,
I learned that SHA-3 (Secure Hash Algorithm 3) is the latest member of the Secure Hash Algorithm family of standards, released by NIST....
-2
votes
1answer
76 views
Is it possible to unhash sha256 if you are given the sha256 and unhash of a variable? [closed]
Lets say that $a, b, c$ are variables and you know that
$$\operatorname{sha256}(a) = b \\
\operatorname{decrypt}(b) = a \\ \operatorname{sha256}(b) = c \\ \operatorname{decrypt}(c) = b$$
Is it ...
6
votes
1answer
2k views
What does the symbol $W_t$ mean in the SHA-256 specification?
I'm really confused about the computation about SHA 256.
$$W_t = \begin{cases}
M_t^{(i)} & 0 \leq t \leq 15 \\
&\\
\sigma_1^{256}(W_{t-2}) + W_{t-7} + \sigma_0^{256}(W_{t-15}) + W_{t-16} &...
2
votes
2answers
333 views
How to prove that finding a cycle in a cryptographic hash function is hard?
I want to show that finding cycles in a cryptographic hash function is hard.
My thought: assume there a black box, that given a cryptographic hash function $h$, finds some $x$ and $r$ in polynomial ...
1
vote
2answers
129 views
Can i generate a SHA512 hash if i know the SHA256 hash of some unknown data?
if the SHA256 Hash of some unknown data is known !
Can i find the SHA512 of that unknown data ?
1
vote
1answer
266 views
Is SHA-256 OK to use for key derivation for a key that is never persisted?
The scenario: On the one side a user enters a pass phrase to encrypt a stream of data (AES-GCM) and a symmetric encryption key is derived from the pass phrase using plain SHA-256 (so not a slow ...
0
votes
0answers
68 views
Is reverse engineering SHA256-HMAC function possible? [duplicate]
Assume HMAC function is used to generate a 6-digt integers time-based onetime password. As follows:
$$K_h =\operatorname{HMAC}(k,t) = H((k\oplus\text{opad})\mathbin\| H((k\oplus\text{ipad})\mathbin\|...
4
votes
2answers
515 views
How can I hash an input into an arbitrary domain point?
I am trying to implement a signature scheme involving RSA signing of a message digest generated by SHA-$256$. I want to hash the input into an RSA domain point instead of the fixed $256$ bit digest ...
-1
votes
1answer
506 views
How to change hash checksum of a text file without changing the contents in the file
I have created a text file called test.txt and the content of the file is Hello World
I would like to change the SHA checksum hash without modifying the contents and filename. Is there any way to do ...
2
votes
1answer
240 views
Is padding of the digest needed in SHA256 with RSA-2048 scheme?
For a signing scheme involving generating a $256$ bit digest using SHA256 followed by RSA with $2048$ bit modulus, the signature would always be 256 bit without padding even though sigantures of up to ...
2
votes
1answer
153 views
What should I use for consequent AES key derivation?
I am writing a small chat program to explore some methods and concepts in cryptography and currently I am using a shared AES key tunneled with RSA which upon further reading revealed many flaws both ...
2
votes
2answers
196 views
Does the knowledge of SHA256(secret) and SHA256(secret + known constant) give any information about the secret just SHA256(secret)?
Does knowledge of SHA256(secret) and SHA256(secret + known constant) give any information about the secret than just SHA256(secret)?
2
votes
1answer
102 views
Is it possible to guarantee a SHA-256 hash will begin with a certain 3 bytes?
I've found this online currency someone has built as a project and it's "miner" / Proof of Work algorithm is as follows:
Generate 32 bytes of random data and hash it, store the original value and the ...
18
votes
2answers
5k views
What makes SHA256 secure?
For example, RSA relies on a mathematically hard problem, factoring, while ECDSA or similar rely on discrete logarithm problem.
What makes SHA256 and similar hash functions, of the same family, ...
8
votes
1answer
1k views
What is the use of SCRAM-SHA-256 (over SCRAM-SHA-1)?
The Salted Challenge Response Authentication Mechanism (SCRAM) specified in RFC 5802 can use arbitrary hash functions to operate. The base version from RFC 5802 uses SHA-1.
From my understanding, ...
2
votes
1answer
79 views
For two LUKS volumes made with the same password, can stealing the encryption key from one volume allow access to the other?
A running computer has two LUKS volumes that were made with the same password. One volume is open (key is in RAM), the other is closed.
If the running computer is stolen, is the closed volume safe?
...
0
votes
1answer
65 views
How to name a signature algorithm that has no hashed component
I have an API-based service that digitally signs messages with RSA or ECDSA (system decides during runtime). The input is base64 encoded SHA-256 hash and the output is:
signature of this hash
...
0
votes
1answer
101 views
What pieces of information do you need to unhash a key to find out the original message?
I am very new to the hashing world and despite hours of research (AKA Googling) I still don't understand this piece of information. What are the different pieces of information that are needed in ...
0
votes
1answer
317 views
Use partial hash to verify entire hash
I've had an idea about storing parts of SHA256 hashes and I'd like to find out how secure it is, or how much less secure it is than storing the entire hash.
For example, users can share this list of ...
0
votes
1answer
1k views
Hash Collision Probabilities
Please give help! how can I calculate the probability of collision? I need a mathematical equation for my studying.
Assume, I am using SHA256 to hash 100-bits. Thus:
SHA256 {100} = 256-bits (hash ...
-1
votes
1answer
2k views
Is it possible to convert the output of sha256 hash to binary or decimal value? [closed]
Can the output value of the sha256 hash function be converted to binary or decimal number? I know that the output is a set of 256bits. Is it possible to convert the output data to an unique ...
4
votes
2answers
331 views
If you wrote a reversible SHA-256 algorithm, how many “metadata” bits would be required for reversability?
I was reading about reversible computing while thinking about FPGA circuits. I realized that it would be possible to write a reversible SHA-256 algorithm if you stored some additional information as "...
17
votes
1answer
3k views
What are the consequences of removing a single byte from a sha256 hash?
I'm working on a system (Ethereum) where it is significantly cheaper to store 32 bytes than 33 bytes. I'd like to create a table where data is stored based on its hash.
Sha256 would meet this ...
