SHA-2 is a family of cryptographic hash functions designed by the NSA and published by NIST in 2001. The family includes various output lengths (224, 256, 384, and 512 bits). The SHA-2 family will eventually be replaced by the winner of NIST's hash function competition.
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Is Wikipedia's table about SHA-2 collisions correct?
I was looking a Wikipedia article on SHA-2, and the "Comparison of SHA functions" table seems to indicate that SHA-2 is less secure than SHA-1.
Is this true, or is the table wrong / misleading?
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1answer
185 views
What does Maj and Ch mean in SHA-256 algorithm?
I'm guessing they're some kind of standard function but what do they do and what do the names mean? A little explaination or link me to an article would be great.
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137 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
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0answers
70 views
Why do we always append padding bits in SHA-512? [duplicate]
Possible Duplicate:
In the SHA hash algorithm, why is the message always padded?
I'm reading the book Network Security Essentials written by William Stallings.
To create a message digest ...
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1answer
190 views
Using SHA-256 with different initial hash value
FIPS 180-3 defines the initial hash value for SHA-256 as the first 32 bits of the fractional parts of the square roots of the first 8 primes 2..19. What would be the risks of using a different value ...
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2answers
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“SHA-256” vs “any 256 bits of SHA-512”, which is more secure?
In terms of security strength, Is there any difference in using the SHA-256 algorithm vs using any random 256 bits of the output of the SHA-512 algorithm?
Similarly, what is the security difference ...
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1answer
391 views
Are there any known collisions for the SHA-2 family of hash functions?
Are there any known collisions for the hash functions SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512?
By that, I mean are there known values of a and ...
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1answer
185 views
How to represent a 32-byte SHA2 hash in the shortest possible string?
I'm calculating a SHA2 hash of a certain sensitive key value. I need to store files on disk using this hash a directory path prefix. So lets say I hash the key value 150023, I get a 32-byte value ...
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0answers
27 views
SHA-512 hash collisions [duplicate]
Possible Duplicate:
Is SHA-512 bijective when hashing a single 512-bit block?
Is there any guarantee that there are no collisions for all 512-bit input values for SHA-512(Every 512-bit ...
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4answers
2k views
Does the SHA hash function always generate a fixed length hash?
I'm using the SHA1/2 family of algorithms for a particular project. I'm was wondering if all the SHA algos return a fixed length hash regardless of the length of the data?
4
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4answers
264 views
Are derived hashes weakening the root?
Given a root hash
root = H(plaintext)
and two (or more) derived hashes
h1 = H(salt1 + root)
h2 = H(salt2 + root)
would the ...
3
votes
3answers
590 views
A simple block cipher based on the SHA-256 hash function
I've come up with this little routine for doing encryption using the SHA-2 (in this case SHA-256) hash function. As such it is a block cipher with a 256 bit (32 byte) block size and an arbitrary key ...
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4answers
503 views
Is SHA-256 secure as a CTR block cipher?
Generate a 256-bit random nonce. XOR it with a 256-bit reusable symmetric key. This is x.
We represent numbers in simple binary instead of a counting function. ...
3
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1answer
162 views
Is the last step of an iterated cryptographic hash still as resistant to preimage attacks as the original hash?
Considering a cryptographic hash, such as MD5 or SHA2, denoted by the function $H(m)$ where $m$ is an arbitrary binary string, there is a lot of material available that deals with potential weakness ...
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7answers
1k views
Is calculating a hash code for a large file in parallel less secure than doing it sequentially?
I would like to improve the performance of hashing large files, say for example in the tens of gigabytes in size.
Normally, you sequentially hash the bytes of the files using a hash function (say, ...
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2answers
541 views
Is SHA-512 bijective when hashing a single 512-bit block?
It's been said that CRC-64 is bijective for a 64-bit block.
It the corresponding statement true for SHA-2?
