Questions tagged [sha-512]

SHA-512 is part of the SHA-2 family of hash functions with a 512-bit output and a 256-bit security level.

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59
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4answers
44k views

SHA512 faster than SHA256?

I'm getting this strange result that SHA512 is around 50% faster than SHA256. I'm using .net's SHA512Managed and SHA256Managed ...
51
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2answers
16k views

Is truncating a SHA512 hash to the first 160 bits as secure as using SHA1?

I am from a web development background (I don't know an awful lot about cryptography or how the algorithms themselves work), so I am asking this question in simple terms. Consider a hash of the word '...
30
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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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3answers
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Dropbox Password security

Dropbox have recently published How Dropbox securely stores your passwords Is this really more secure than using bcrypt with a complexity of 11 or 12 ? The password "chain" is secure as its weakest ...
17
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2answers
9k views

Are the SHA family hash outputs practically random?

Say I hashed the output from a random number generator (with nonce), would the resulting SHA256 hash be as random as the inputted number? And If I used the first 5 hex characters, and then used the ...
14
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3answers
2k views

Is there a way to use bcrypt with passwords longer than 72 bytes securely?

From my understanding BCrypt truncates the password to 72 bytes. If a password is longer than 72 bytes, what is a way to store that password using bcrypt securely without compromising it? Or is this ...
13
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1answer
7k views

Is there any benefit from using SHA-512 over SHA-256 when AES just truncates it anyway?

I am still not very clear on how AES-256-CBC can use SHA-512 bit keys, but I assume that it just truncates the 512bit hash down to 256bit. In software like GnuPG and OpenPGP, is there any real benefit ...
12
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1answer
352 views

Does SHA-512 leak info about SHA-256?

Does the SHA-512 value of an input leak any information about the SHA-256 value of that same input? Specifically, if I'm using SHA-512 to derive encryption and HMAC keys from a 256 bit ECDH shared ...
11
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4answers
2k views

Why is SHA-512 limited to an input of $2^{128}$ bits?

Both SHA-384 and SHA-512 are limited to an input size of less than $2^{128}$ bits. Considering SHA-512 has a higher output size, couldn't it include more input data?
11
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3answers
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Is deriving the IV from the password secure?

I came across an encryption scheme to encrypt files with AES-256. You can see the initialization of the decryption routine below: ...
9
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2answers
473 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 ...
8
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1answer
2k views

Does salt size affect password hash security?

I use PBKDF2-SHA512 with an iteration count of 128,000 to hash my passwords. I use a CSPRNG to generate a salt per password. However, I am unsure about the ideal size of the salt. I have read a lot of ...
7
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1answer
1k views

Significance of rotation constants in SHA-512?

In a single round of SHA-512, in the operations $\Sigma_0(A)$, $\Sigma_1(E)$ why are the constants $28$, $34$, and $39$ used for the number of rotations? What significance do these numbers have? What ...
6
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2answers
3k views

Why might SHA-384 throughput be lower than SHA-512 throughput in hashcat and more secure?

I found a hashcat benchmark results in the internet: hashcat results: SHA-384 is 17065.4 MH/s SHA-512 is 17280.3 MH/s Why does SHA-512 take less time? SHA-512 is longer and I thought it therefore ...
6
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5answers
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Would it be possible to generate the original data from a SHA-512 checksum?

So, I have a file that is XY Exabytes big. I create a SHA-512 hash from it. Are there any theoretical chances that I can retrieve the original data just from the sha512 hash? Also, are there any ...
6
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1answer
2k views

Transforming SHA-512 into SHA-512/256?

Based on my skimming over FIPS 180-4 it looks like the only difference between SHA-512 and SHA-512/256 is the initial hash value and the fact that the final output is truncated to 256 bits. My ...
4
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1answer
7k views

Benchmark differences between SHA-512 and bcrypt

So I recently made a benchmark SHA-512 vs bcrypt with hashcat CUDA. Here are the results : ...
4
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1answer
141 views

Is it possible to work out the hash using length extension attack but with different hashes type?

For example, I have: Unknown: A secret variable, lets call it secret, that is unknown to me Known: The length of secret, (lets ...
4
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1answer
257 views

Worth taking performance hit of HMAC to gain additional security?

It seems like SHA-512 truncated to 256 bits is usable as a MAC [1]. The advantage is that it's ~50% faster than HMAC-SHA-256 on 64-bit CPUs and ~50% faster than HMAC-SHA-512 on short inputs. (My use ...
4
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2answers
6k views

SHA512withRSA - Looking for details about the Signature Algorithm

I am trying to find information about the Signature Algorithm SHA512withRSA and have been unsuccessful so far. In the current state, the signature is too long, so I would like to check the code for ...
3
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1answer
3k views

Why are these specific values used to initialise the hash buffer in SHA-512?

I'm reading the book Network Security Essentials written by William Stallings. To create a message digest with SHA-512, we have to go through some steps: append padding bits. append length ...
3
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2answers
2k views

Combine two sha512 hashes to a single hash

Assume I have two data fragments: $Frag_1$ and $Frag_2$. I can build sha512 hashes the usual way with $SHA512(Frag_1)$ and $SHA512(Frag_2)$ and then hash the two fragments appended to each other: $$...
3
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2answers
896 views

Vigenère cipher with sha512 and a little foresight turns to one-time pad. How safe can be?

I'm doing some exercises and of course I have read about the weaknesses of Vigenère cipher because it repeats the key. But what if I use a different hash every time? The hash of the "key + an ...
3
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2answers
286 views

Is it possible to generate an infinite number of collisions given an infinite amount of strings?

Let us assume that we have a string $w$ such that it belongs the set $C$, where every member of $C$ is not null, and contains every string of characters that can be permuted (numbers, letters etc.). ...
3
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2answers
241 views

What is the purpose of placing the most significant byte first?

When the SHA algorithm states "A block of 128 bits is appended to the message. This block is treated as an unsigned 128-bit integer (most significant byte first) [emphasis added] and contains the ...
3
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1answer
76 views

What is SHA-512's input space, taking into account variable message size?

The SHA-512 hash function accepts any message from a single bit to $2^{128}$ bits. Because the function takes into account the message length, I can't just represent every message as a $2^{128}$-bit ...
3
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2answers
155 views

What is the proof that a hash output contains random binary numbers

I have heard quotes by many that a SHA-512 hash output is random. Does anyone know what method was used to come to this conclusion? If it is not randomized, how could that be shown?
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2answers
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What is the length field in SHA-512 padding?

If I am using SHA-512 on a message and need to determine the padding field and length field, how do I determine the length field? I think I understand the padding, but not the length field. For ...
3
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1answer
993 views

How does the HOTP dynamic truncation function generalize to longer hashes?

HOTP, the HMAC-based One-Time Password algorithm from RFC 4226, uses a "dynamic truncation" function to turn the 20 byte HMAC-SHA-1 value into a 31 bit string. The dynamic truncation (from Section 5.3)...
3
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2answers
1k views

Using bcrypt derived keys for encryption?

Sorry for this ignorant question but I am currently weighing up the advantages and disadvantages of BCrypt over PBKDF2 and from what I have read BCrypt is considered more secure but from what I have ...
3
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1answer
2k views

estimate of time required to crack sha512crypt password with JtR + OpenCL

OK, I have a shadow file with a password that I know, it is 4 letters followed by two numbers. Using John The Ripper with OpenCL support, on a laptop with AMD Radeon Mobility graphics, how long would ...
3
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1answer
183 views

Why is SHA2 used for file verification if it's susceptible to length extension attacks?

Am I misunderstanding length extension attacks, or is there some different reason, or is it really a bad idea to use SHA2 for file verification? If the answer is that it's really a bad idea, would ...
3
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1answer
1k views

Standard hash function of Linux

So I went through my /etc/shadow file in Linux and discovered that my passwords were stored in SHA-512-based crypt ('sha512crypt') mode, so SHA-512. But why? I mean ...
3
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1answer
619 views

Change initial hash value of SHA512/t

Fips 180-4 defines under 5.3.6 how to calculate initial hash values for SHA512/t for a given value t. Can someone explain me how the t actually affects the outcome of the procedure (which, as far as I ...
3
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1answer
226 views

Given a sha-512 hash of a value picked at random from the $2^{128}$ key space, how hard would it be to recover the original value?

More specifically is it reasonable to assume that someone with the resources of a state actor can feasibly compute a rainbow table of all the sha-512 hashes of values within the $2^{128}$ key space? ...
3
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1answer
649 views

Padding password before SHA-512 hashing to avoid info leak via timing

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 ...
2
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1answer
2k views

Are there ANY text strings that will generate the same SHA-512 Hash output? [duplicate]

Are there ANY text strings that will generate the same SHA-512 Hash output? Please provide an example, and how you came to that conclusion. I've tried thousands of variations, including ".." vs. "." ...
2
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2answers
1k views

HMAC-SHA512 output randomness?

This is regarding an online roulette game that claims to be fair. Here is the explanation: Two strings are created: ...
2
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3answers
452 views

How much original entropy is lost if a part of the hash is known?

You have an entropy source of n bits You hash it with SHA-512 for example k bits of the SHA-512 output are publicly revealed, ...
2
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1answer
2k views

Using a SHA512 hash to encrypt data

How can I judge the level of security with the following algorithm: I create a 64 byte hash using SHA512 via some input. I use this hash to iterate over the plaintext, byte by byte, and similarly ...
2
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1answer
99 views

Calculate new hash from old hash + appended string

If I have a hash of some string in the form: hash(UNK + "known"), Is there a way to calculate the hash of (UNK + "known" + "append"), given the hash of the original value? Specifically I'm asking ...
2
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1answer
378 views

Does this protocol provide Perfect Forward Secrecy / are there potential security flaws?

We have a HMAC key (128 bit/16 bytes) an AES key (128 bit/16 bytes) an AES IV (128 bit/16 bytes) a random salt (128 bit/16 bytes) Each packet is signed with a HMAC (SHA256) After each packet is ...
2
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1answer
746 views

Is this approach to generating a “random” number from a sha512 hash effective?

I'm looking to run a small raffle but i'd like people to be able to verify that the number chosen was fair. I know some sites use a "Provably Fair" system to achieve this where user input is combined ...
2
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1answer
1k views

Hash length extension attack - SHA256 to 512 - impossible, correct?

Just want to be sure about something before I sign off on a method we're about to put into place. We have a secret, to which a user-defined key is appended. The user can see the SHA256 hash of the ...
2
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1answer
57 views

How to compute initial buffer of SHA-512?

I'm reading Cryptography And Network Security of William Stallings. In the SHA-512 section it is said that there is a 512-bit buffer is used to hold the intermediate and final result and every 64-bit ...
2
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0answers
446 views

Need help to get correct TOTP [closed]

I am really confused and need help on this problem related to TOTP as specified in RFC6238 here: https://tools.ietf.org/html/rfc6238#section-1.2. So I am now given a task to implement the RFC6238 to ...
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4answers
897 views

I think PBKDF2 may be better than Scrypt? Looking for someone to point out my logical error

People seem to mostly recommend scrypt these days, but I'm not sure if this should be the case? I'll structure this post by just making an argument for PBKDF2 over Scrypt and then you can reply ...
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2answers
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Are there parts of a SHA-512 hash that occur more often then others?

Suppose I have a 'begin' password that I can remember. I calculate it's SHA-512 hash, transform it to base-64 and check if it has a least 1 lowercase, 1 number, 1 capital, and 1 sign. If this is not ...
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2answers
129 views

PBKDF2 with SHA-256/512 for low entropy input?

Is there any reason to use something stronger than SHA-1 with PBKDF2 if my input is fairly low entropy? I.e. if the passwords being hashed are only about 30-bits of entropy. I can't find it now, ...
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2answers
211 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 ?