Questions tagged [sha256]
Sha256 is a hashing algorithm.
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Are short messages hashed with a HMAC insecure?
Imagine I were to provide a person with a single letter "A" and the HMAC-SHA256 hash of this message, keyed with my secret key.
Would this person be able to derive any information about my secret key?...
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30 views
Does transmitting short, predictable plaintext along with the HMAC signature of that text present a security risk
In order to allow clients to verify responses originating from our server, we are generating an HMAC signature of the body and a timestamp, and attaching it as a header. The timestamp is also attached ...
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3answers
842 views
How can I find a SHA-256 hash with a given suffix using hashcat?
Recently we competed in the X-MAS 2019 CTF and many of the challenges included a proof of work (PoW) check to avoid Denial of Service (DoS) attacks against their servers. The most common was we were ...
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3answers
110 views
Using two salts - one stored with the password, one stored in a random row in a separate table
Imagine a login system is being created, and a user's password is hashed thusly:
Users.password = PBKDF2(salt1 + password + salt2)
The result of that ^ operation and salt1 are stored side-by-side in ...
0
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2answers
55 views
multiple call of gcry_md_write function
May be it 's not a question for information security stack exchange and if it's true excuse me for my mistake.
I want to understand how this code works:
char *s = "1";
char *s_2 = "2";
unsigned ...
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3answers
72 views
Can the username be used in HMAC during client-side hashing?
I am very new to authentication and cybersecurity in general, so I apologize if I have anything completely wrong.
My goal is to have the client side hash passwords before sending them to server side ...
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0answers
46 views
Is it safe to share an Azure SAS token with an untrusted client?
We need to host files in Azure Blob Store, and allow access to end users to their generated "statements"(pdf) for a short period of time.
We're considering achieving this by generating a short-lived ...
0
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1answer
97 views
Does it increase security to hash a SHA1 hash with a common salt with SHA256 with individual salt [duplicate]
I tried to find a similar question but I did not find a question describing my exact scenario and I am still puzzled if the following actually makes an application more secure.
I have legacy ...
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67 views
How to verify a binary correctly even if my github account is hacked by someone
I have a binary file and saved it on github release page. https://github.com/zono/bolt8/releases
To allow users to verify it, I saved sha256sum and signature(.asc).
However I have a concern that if ...
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0answers
438 views
Secure Http Connection With Authentication Header
I am trying to create an authentication header algorithm that can be used for authentication on HTTP server.
Not sure it is good but it seems OK to me. I also used similar approaches for previous WS ...
3
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1answer
247 views
Crack 8-char password with known number of set bits
At University, I got some CTFs to do for my security lectures.
Basically, I need to crack an 8-character password (96 possible characters). I know that 42 of the 64 bits are set to 1 and I know the ...
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3answers
305 views
Which function to hash 128 bit API key with?
I'm generating 128 bit API keys. AFAIK 128 is totally secure for generated key. In the DB I want to store hashes, not the plain text (to be protected against DB leak), but what hashing algorithm ...
0
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1answer
245 views
I need to compute a string whose SHA256 hash matches a given prefix. How should I approach it? [duplicate]
Is there any (more efficient) way for computing any string with a given prefix in it's SHA 256 hash? And how probable am I to stumble on such a string if I brute force?
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132 views
Does the password goes weaker as they get longer since hash has a fixed length? [duplicate]
For example, sha256 has a fixed hash length of 64 characters. So I'm wondering will a password goes weaker as they get longer and longer? Since no matter how long your password goes, the sum will be ...
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6answers
2k views
How likely is a collision using MD5 compared to SHA256 (for checking file integrity)?
Many sites these days offer MD5 and SHA256 hashes to check the integrity of downloaded files or archives.
I wonder how much safer is the use of the SHA256 hashes for integrity checks?
Note: Consider ...
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1answer
70 views
How are these transaction fingerprints colored?
For those unfamiliar, blockchains have two main types of data structures propagated in their networks: blocks and transactions. Each block and transaction has a hash, just like key fingerprints. The ...
0
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3answers
306 views
Is it easier to calculate a partial SHA256 collision than a full one?
Question: Disregarding brute-force, is it any easier to calculate a partial hash collision, in which only a certain number of bits match?
Reasoning: On many websites you find hashes for file ...
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1answer
354 views
Error detection capability of SHA-256
If we use SHA-256 checksum to detect corruptions to a file, what is its capability in terms of missed errors?
For example, reading the page about error correction and detection here, under the ...
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0answers
413 views
How to mask attack a sha256 hash with following information using hashcat?
I am hashcat newbie and I want to crack a hash :)
The answer is 1-15 (unknown) characters and it may contain 'a-z' 'A-Z' '0-9' and '_' . (A Twitter username)
How may I mask attack a hash with above ...
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2answers
5k views
Why is SHA-256 not good for passwords? [duplicate]
I've just started learning about all of this and I can't really find an answer for that anywhere, namely why is SHA-256 not used for passwords? I found that the reason is that because normal SHA-256 ...
1
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2answers
70 views
Confusion about the software and also the digital signature getting modified
I'm not sure what is very secure about digitally signing a software or firmware to distribute. I understand the benefit in that it can let the receiver know if the data accidentally got corrupted ...
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1answer
322 views
Is it possible to tell if a file's message digest is MD5 or SHA-256?
There's some old data encrypted with OpenSSL 1.0.2, but now OpenSSL is at 1.1.0. I understand from OpenSSL FAQ USER3 that an old file can be decrypted with 1.1.0 by using -md md5. But let's say you ...
2
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1answer
7k views
How to decrypt a gpg file?
I have a gpg file and a sha256 file. When I try to decrypt the gpg file using the gpg - d file.gpg command, it says that there is no secret key. I am absolutely new to this so I would appreciate any ...
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1answer
824 views
when should i use HMAC-based JWT?
I read a number of blog posts and found that it is tough to keep the secret-key a secret and if using a symmetric algorithm for JWT creation, the generator has the power to create as well as validate ...
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1answer
118 views
SHA256 Encrypting with Value [closed]
Is it possible to encrypt a value (such as "hello world") with itself ("hello world") using an encrypting technique such as SHA256? Is that safe to do or would it be easily compromised?
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2answers
242 views
Sha256 hash + secret GUID + RNGCrypto random number to hash passwords
I'm maintaining a website which uses Sha256 hashing of passwords.
The passwords are hashed with a GUID key, and a RNGCrypto generated random salt.
I'm just trying to understand the security risks ...
0
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2answers
739 views
Generating salt for hash that occurs on server and client
Let's say I have an API call which is supposed to check if email address exists in the DB, without transmitting the actual email address.
For that purpose, I've decided to store SHA256 hash of the ...
3
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2answers
528 views
Can AES and SHA-256 outputs with the same inputs be used to break each other?
An abstract representation of my question looks like this:
byte[] encrypted = AES.Encrypt(bytesToEncrypt, password);
byte[] hash = SHA256.Hash(password);
If an attacker obtains the values of both ...
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5answers
13k views
Is it secure to use MD5 to verify the integrity of small files (less than 15kb)?
I know that collision for MD5 has been documented since the 90s and that digital certificates based off of MD5 has been demonstrated to be completely compromised back in 2010 but how effective is MD5 ...
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3answers
231 views
Should Hashes of Sensitive Data be Encrypted
I'm planning on storing chunks of encrypted data inside a file, along with each chunk would be the hash(sha256) of the unencrypted chunk stored in the file as well. Is storing the hash secure?
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2answers
613 views
Is it safe to use a Windows executable with expired SHA256 certificate but valid SHA1 certificate?
Microsoft's Media Creation Tool to create Windows 10 installation media has a SHA1 digital signature and a SHA256 digital signature (shown via file properties). However, the certificate for SHA256 ...
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2answers
2k views
Decoding a HMAC SHA256 when the key is the same as the original string
Theoretically, python function for encrypting a HMAC SHA256 looks like this:
hmac_sha256(key, text)
The word "hello" was encrypted using the function like so:
hmac_sha256("hello", "hello")
How ...
0
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3answers
139 views
Producing secure hashes to detect data manipulation
I have an Android app that internally relies on a SQLite database that stores encrypted user data. The data is encrypted using AES-256, with a key generated by the PBKDF2-HMACSHA256 algorithm. The ...
2
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0answers
101 views
How bad is it to generate passwords via sha256, rather than storing them with a pw manager? [duplicate]
I've been pondering how to deal with passwords lately. I'd been using a password manager for awhile, but this means I can't access anything I use it for from a machine where it isn't installed (or ...
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3answers
813 views
Hashing a large file on an embedded system
I'm trying to come up with a way to verify the authenticity of a file that I'm downloading from a server to an embedded system. I'm thinking of using a hash (SHA256 preferably). My main concern is ...
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4answers
4k views
Is using 100,000 iterations of sha256 good enough for password storage? [duplicate]
I am creating a web app, and I was wondering if it would be secure to use 100,000 iterations of sha256 for storing passwords? I know that there are algorithms such as scrypt and bcrypt, however, I was ...
3
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1answer
211 views
How is the bitcoin block header data padded for SHA256 hashing?
I see that a block contains 80 bytes. SHA256 expects integral multiples of 64 bytes as input. How are the remaining 48 bytes calculated?
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1answer
2k views
HMAC-SHA256 for JWT Token Signature
I am currently working at a company in which we have the need to design a token based authentication system. We will be the owners and controlers of two servers, one being the authentication server ...
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1answer
411 views
Interoperability of openssl smime, rsautl & dgst
How do
$ openssl smime -sign -in test -text -out mail.msg -signer mycert.pem -inkey key.key
and
$ openssl rsautl -sign -inkey key.key -out test.sgn -in test
and
$ openssl dgst -sha256 -sign key....
2
votes
1answer
112 views
E-Mail signature examination
If I download a signed e-mail from thunderbird, it looks like this:
Content-Type: multipart/signed; protocol="application/pkcs7-signature";
micalg=sha-256; boundary="------------...
2
votes
2answers
87 views
Analysis of gpg2 packets
I want to mentally visualize or just understand a gpg-signature.
When running
$ gpg2 --list-packets --verbose < test.sig
the output is
# off=0 ctb=89 tag=2 hlen=3 plen=540
:signature packet: ...
3
votes
2answers
490 views
Why are passwords sent unhashed by most modern websites? [duplicate]
I've been investigating various protocols used to send usernames and passwords to web servers in order to authenticate, and while obviously all of them these days use SSL/TLS, I was a bit surprised to ...
4
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1answer
336 views
Is appending a salt before hash generation enough
I have what I think is a securely generated salt/hashing mechanism for HMAC authentication based on SHA256 in place. However, I'm using the salt in, from what I can see, a fairly standard way of just ...
0
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1answer
144 views
Given a hash value, is it possible to determine the length of the initial string that was digested? (SHA256)
Also, given two hash values, is it possible to determine if either one of them was a result of digesting a larger string?
As far as I understand SHA256, nothing but guessing the string itself helps. ...
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0answers
628 views
ways to check a certificate fingerprint against known logs
Suppose I have a certificate sha-256 fingerprint, which I can obtain say visiting the relevant domain in firefox or from a shell script using openssl, and i want to verify this fingerprint. one option ...
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1answer
313 views
compare sha-256 fingerpirnt of certificate with google transparency report
Say that I want to check an https certificate. Suppose I know its SHA-256 fingerprint, how do I compare it to this service search tool, which apparently only gives me the serial number?
edit1: can ...
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2answers
354 views
Inconsistency Among MD5, SHA1, and SHA256 Hashing Protocols
There appears to be an inconsistency (or unpublished protocol) in many online hash generators when formulating a hash from an uploaded text file, versus strictly hashing the contents of a file. This ...
0
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1answer
98 views
Can a secret, S, be efficiently recovered from a list of usernames and SHA256(S + username)s?
Given a set of usernames and their corresponding proofs of knowledge of a shared secret: SHA256($SECRET + username), can an attacker recover $SECRET more efficiently than by brute force?
(This is ...
1
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1answer
760 views
SHA256 for IV for AES-256 CBC?
When making an IV for AES-256 CBC mode the IV should be random and shouldn't be able to be guessed.
If I were to use the rand() function in C, seeded with time(NULL) to generate sim random numbers ...
6
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2answers
11k views
Is SHA-256 + Salt still safe for password storage? [duplicate]
I am developing a website which requires users to register to it in order to use it's functions and I was wondering if SHA-256 + salt (random salt provided by RNGCryptoServiceProvider in C#) is ...
