Linked Questions

4 votes
1 answer
1k views

Is SHA-256 a one way permutation when restricting the domain to {0,1}^256? [duplicate]

Suppose we consider the space of $\lbrace 0,1 \rbrace^{256}$ as the domain and SHA-256 as our hash function. Does SHA-256 become a one way permutation? Has anyone tried to prove this? Or can it be ...
torrho's user avatar
  • 187
0 votes
2 answers
1k views

If I compute the SHA-1 of all possible 40 digits hexadecimal strings, will I get all possible sha1 hashes? [duplicate]

Wikipedia says sha1 produces a 160-bit (20-byte) hash value. So if I compute the SHA-1 of all possible SHA-1 values, which as far as I understand is at current time impossible both to calculate and ...
guest22's user avatar
3 votes
0 answers
168 views

Is SHA-1 collision free on data up to 20 bytes long? [duplicate]

Is SHA-1 collision free on data up to 20 bytes long (lenght of hash / internal state)? That means that every input produce unique output, but you surely know that, i just write it in order my question ...
Smit Johnth's user avatar
  • 1,691
3 votes
0 answers
78 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 input has ...
nanofarad's user avatar
  • 131
1 vote
0 answers
50 views

Number of unique outputs in hash function (SHA256) against all possible inputs [duplicate]

If I use SHA256 as a hash function, and I try all inputs starting from 0 to 2^256 (means all possible combination of 256-bit), then will it give me 2^256 unique output without any collision? Or ...
Puneet Kumar Kaushal's user avatar
22 votes
4 answers
3k views

Cycles in SHA-256

Let's say I start with a particular 256 bit value. Call this $v$. I then hash that value, and get another 256 bit value. Call this $\text{SHA256}(v)$. I take this value and get another 256 bit value. ...
bnsh's user avatar
  • 323
15 votes
7 answers
5k views

Is it theoretically possible to construct a string that contains its own hash value?

After saw the xkcd comic Self-Description, I wonder if it is theoretically possible to construct a self-descriptive string that contains its own hash value? Let's say the string's MD5 value is ...
Mys_721tx's user avatar
  • 253
9 votes
4 answers
6k views

What alphanumeric string length can be used to guarantee no hash collisions from CRC-64? [closed]

If I'm hashing alphanumeric strings (chars in the set 0-9, a-...
brandx's user avatar
  • 193
7 votes
3 answers
5k views

Is Base64(SHA1(GUID)) still unique like the original GUID?

Basically what the title is; GUIDs are unique by design. If you run the GUID through SHA1 and then Base64 the hash, will the resulting string have the same guaranteed uniqueness as the GUID, or not?
John's user avatar
  • 173
15 votes
2 answers
3k views

Are cryptographic hash functions perfect hash functions?

For a cryptographic hash function and input values of shorter length than the hash function output, it's pretty obvious that there should be as few collisions as possible. But are there guaranteed to ...
lxgr's user avatar
  • 1,788
8 votes
2 answers
1k views

Determine whether bit sequence is hash?

I would like to know whether it is possible to determine whether a value of for example 256 bit length is a SHA-256 hash or a random, equally distributed value. Is ...
Julian Bruckner's user avatar
7 votes
4 answers
2k views

How many recursive md5 hashes are needed to always get same string

If we start with a set of possible input values, and apply the md5 algorithm to all elements of this set and then filter out the unique results (a.k.a. filter out ...
Thijs Riezebeek's user avatar
2 votes
1 answer
3k 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. "." ...
synicalsyntax's user avatar
10 votes
2 answers
1k views

Just how surjective is a cryptographic hash like SHA-1?

From “Are common cryptographic hashes bijective when hashing a single block of the same size as the output” and “How is injective, inverse, surjective & oneway related to cryptography”, it is ...
Paul Uszak's user avatar
  • 15.5k
3 votes
2 answers
479 views

Are Hash Palindromes Possible?

I'm trying to figure out whether the following is impossible or merely improbable: Does there exist an input, I and its hashed value, ...
John Ruiz's user avatar
  • 133

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