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.
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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, ...
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Digital Signature Verification failed using SHA256withRSA in Python [migrated]
I am trying to validate the digital signature with given certificate files for the offline aadhaar KYC verification application.
This instruction is given in the documentation for the verification.
...
6
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1answer
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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, ...
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1answer
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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?
...
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Password recovery on Block-chain ( Hyperledger sawtooth in this case)
I am using bip39 specifications for 24-word mnemonic, Whenever user registers with his/her password, A Scrypt key is generated from this password and used to encrypt this mnemonic, The admin of the ...
0
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1answer
42 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
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1answer
37 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 ...
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1answer
55 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 ...
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1answer
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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 ...
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1answer
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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 ...
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2answers
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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 "...
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1answer
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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 ...
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1answer
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11answers
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How do hashes really ensure uniqueness?
This might seem an impractical and unnecessary conversation, but I feel it's something I need to clarify. Especially, as I just got my first developer job in a blockchain startup.
So hashes are said ...
3
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1answer
247 views
Is SHA1 secured enough as a PRNG
I read SHA1 is still a secured hashing function with no collision found as of now. However, it's just a matter of time for someone to come up with such a collision or attack. Therefore, in new ...
2
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1answer
131 views
Practical quantum attacks on SHA256 MAC and HMAC
Is SHA256 MAC (or HMAC) vulnerable to any quantum attacks?
Game setup:
The attacker's goal is to produce a valid MAC to be accepted by other devices in the ecosystem. The ecosystem consists of ...
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2answers
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Can I find the IV of a single block of SHA256, given the plaintext and digest?
Each 512-bit block of SHA256 takes an initialization vector (IV) and message schedule and returns a digest. Knowing the message schedule and resulting digest, is it feasible to reverse the algorithm ...
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5answers
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How many hex digits do I need to compare when manually checking hash functions?
I sometimes run sha256sum on large files after transferring them from one place to another, and will just skim the hash output to verify it's correct. But, I usually just look at the first/last 5 or 6 ...
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1answer
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Signing with RSA-SHA256 algorithm using EC keys
Is it practical to sign a data using RSA-SHA256 algorithm with EC keys?
I used a small NodeJS script and crypto module (uses openSSL internally) to test this and I could successfully sign the data ...
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2answers
171 views
VeraCrypt a weak point [closed]
Biggest flaw in VeraCrypt(or other Encryption programs) is Hash Algorithm.
VeraCrypt hashes (SHA,Whirlpool,Streebog) it is the only point where can break an encrypted disk. Because break algorithm (...
2
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1answer
69 views
Why is a 1 added after the message input and before adding padding zeros (if necessary) when using SHA256 or RIPEMD160? [duplicate]
In preparing an input for SHA256 or RIPEMD-160 a single bit (1) is appended to the message before adding any necessary zero padding and before adding the bitlength (64 bits) to form 1 or more 512 bit ...
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1answer
119 views
SHA's finite character set and collision
From what I've researched, SHA's hex encoded string contains the characters [a-fA-F0-9]. If we represent it in Base64, it can contain ...
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1answer
57 views
Does having an SHA256 hash compromise PBKDF2 secrecy?
If I have a password pwd, and I hash it with SHA256 and send it to a server for authentication (server will apply ...
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2answers
396 views
Which attacks are prevented by the different initial hash values for SHA-2 with truncated output?
NIST specified SHA-2 hash functions with truncated output. Those hashes use different initialization values than SHA-256 or SHA-512. SHA-224 is based on SHA-256. SHA-384, SHA-512/224 and SHA-512/256 ...
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2answers
110 views
Possible SHA-256 implementation weakness
I came across a SHA-256 implementation that seems not to conform to the standard and because I can't change the implementation I would like to know if it's safe for use or can be a potential weakness.
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0
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2answers
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Can I update sha-256 digest chunk-wise instead of the whole array at once?
I'm not sure whether this questions is about SHA-256 algorithm itself or the particular implementation I'm using.
Usually, a hash algorithm implementation has functions, let us call them update and ...
0
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1answer
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Is it safe to hash a packet with a shared secret to prove authenticity?
I am developing an online game, where the server is written in Node.js and the client uses Godot. The issue is that Godot has no cryptographic functionalities (it can only encrypt and decrypt files, ...
2
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2answers
143 views
Does Diffie Hellman guarantee secrecy?
I am studying my Cryptology exam and one question I got stuck below;
Recall the Diffie-Hellman key establishment protocol. Alice runs this protocol over
the Internet to communicate with Bob. ...
2
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1answer
85 views
SHA-256 Hash identical on two similar but not exact items
There are two discs that we have that have all the same files. However, using a new method for burning the discs, the second disc had modified file dates of 5/30/2018 while the original disc has dates ...
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1answer
246 views
HMAC SHA256 for deriving session keys using random nonce
I need to derive session key in order to create an application layer secure channel between mobile app and a bluetooth device. My scheme is similar to
this scheme that uses a HMAC and counter.
...
4
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1answer
263 views
Is it problematic to use PBKDF2-HMAC-SHA256 to derive a 512-bit XTS key?
PBKDF2 should only be used to generate a larger output than the hash function it uses if the output is used in such a way that it has a flat keyspace. As far as I am aware, XTS does not have a flat ...
4
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1answer
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Are hash functions strong against quantum cryptography and/or independent enough of mathematics?
I work on ethereum and other blockchain technologies. And seeing that quantum pc's are someday going to see the light I have some questions / doubts.
I was wondering if hash functions are strong ...
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1answer
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AES-CBC then SHA vs AES-GCM for encrypting and authenticating a web token
I am trying to have something like JWT but kinda ad hoc and encrypted. The token itself is simply a stringified JSON that contains the user ID and Unix timestamp.
Now, I tried to use AES-128-GCM, ...
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1answer
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How to reversely compute from hash [closed]
What are practical methodologies to derive the following ciphertext:
1bd0d370b262d748b21c40cc7e5746642b4c06079a224c65e443e429289753c2
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2answers
254 views
What would the implications be of a single randomly discovered SHA-256 collision? [closed]
Imagine if someone messing around with hashes accidentally came across two inputs to SHA-256 that produced the same output. Not a concerted effort, not Google/NSA or crypanalysis. No tin foil hats. ...
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1answer
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How are multiple iterations of SHA-256 handled for longer inputs?
I wrote a python program to perform the SHA-256 function. It works just fine until I try to hash longer strings.
If I hash (in HEX)
...
2
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1answer
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Why is modulo being used for congruence in SHA-2 padding when the outcome is always the same?
I am reading up on SHA-2 algorithms and I came across this paper: https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf
In section 5.2.1 it talks about the formula for padding a message. There ...
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4answers
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How can hashes be unique if they are limited in number? [duplicate]
I'm curious, how can for example SHA-256 be unique if there are only a limited number of them?!
For clarification:
how many MD5 hashes are there?
$16^{32}$ MD5 hashes can be produced.
$16^{64}$ SHA-...
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1answer
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Generating AES-256 Private Key from user string
So I wish to encrypt a string using AES-256 and want to provide the user to specify the password for unlocking the string. I plan to use sha-256 to hash to users entered password and use this as the ...
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2answers
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In a very simplistic and step by step example, how do I get the 'w' values for SHA256?
I've been to https://docs.google.com/spreadsheets/d/1mOTrqckdetCoRxY5QkVcyQ7Z0gcYIH-Dc0tu7t9f7tw/edit#gid=1194752368, http://www.righto.com/2014/09/mining-bitcoin-with-pencil-and-paper.html, and https:...
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1answer
279 views
MAC size 128 bits or more?
Just a quick question:
I've seen implemented BouncyCastle's class AeadParameters with MAC length of 128 bits, which was allegedly recommended.
Though when I looked up HMac to implement my own MAC in ...
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2answers
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Why SHA-256 (or any other) is too fast for passwords but “slow” for collisions to be found?
Normally, the standard answers of why passwords shouldn't be stored using a groups of hash algorithms, including SHA-256 or higher, even if salted, are "because they are 'fast' hashes", "the attacker ...
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1answer
57 views
SHA algorithim with different hash value
I am new in hash cryptography. I am trying to build the sha256 hardware accelerator. I am thinking about using the different hash value to optimize the performance. I am trying to fetch custom hash ...
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0answers
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GPG AES-256 Malleability
If Alice encrypts a file with GnuPG software using the AES-256 mode, and sends the encrypted file over an insecure channel (like E-mail or HTTP) to Bob. Both Alice and Bob know the password, but only ...
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2answers
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Optimal way to bind two hashes
Currently I have:
H1 = SHA256
H2 = SHA1
Both H1 and H2 have fixed length. What's the most efficient way to bind H1 and H2 together into H3? The goal is to ...
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1answer
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Security of using sha(secret + rand)
I have come across some security implementations in which party A will compute MD = sha256(secret + rand) and transmit MD and rand to a counterpart B. If the second party knows the secret, then when ...
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2answers
509 views
Probability last character sha256 hash
A quick question. I want to use the last character of a SHA256 hash (blockhash of a bitcoin block) as my random source. Is 100 /16(amount of different chars) = 6.25% true for all characters or are ...
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1answer
229 views
Confused about Merkle Damgard Transform - short messages?
With the Merkle Damgard Transform, how does it handle messages that are shorter than the input message length - hash digest length? Or in other words, how is the last block handled? So for example, if ...
2
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1answer
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Difference between SHA 512, SHA 512 Half, SHA 256
I was trying to create a python wrapper for RIPPLE crypto currency, and i ran into SHA 512 half which i have no idea or reverse googled it to no avail. Can someone help me understand the difference. ...
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0answers
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For any 256 bit string, is there some input to SHA256 that produces this string? [duplicate]
For any random 256 bit string, is there any guarantee that there exists a string which, given as input to SHA256, will produce this string?
