Linked Questions

26
votes
3answers
12k views

Are cryptographic hash functions quantum secure?

I was reading a paper related to post quantum cryptography. It says that RSA, ECC and ElGamal encryption schemes would be obsolete with the advent of quantum computers. But the hash functions can ...
12
votes
2answers
3k views

Is SipHash cryptographically secure?

I'm evaluating different hash algorithms for use in my application. One of the kind of algorithms I am looking at are cryptographically secure ones to protect against DOS attacks. SipHash seems ...
10
votes
1answer
684 views

Collision resistance of hash function built on modular exponentiation

Consider the following hash function family for hashing integers: $Gen(1^k)$: generate 2 $k$-bit primes p,q. Let $n = pq$. Choose random $y \rightarrow QR_n$ and output $n,y$. $H_{(n,y)}(x) = y^x \...
4
votes
1answer
805 views

Is there are a metric based on collisions to compare bad hash functions?

Bad hash functions are not so perfect as in the "general collision probability" hypothesis... And a general concept of "collision resistence" not need the constraint of independence between the ...
3
votes
1answer
547 views

How is pre-image resistance defined, formally?

Earlier today, forest asked in our chat, The Side Channel whether the definition of first pre-image security actually requires that an input that evaluates to the challenge hash result must be known ...
0
votes
1answer
437 views

How to use cryptography to assure data integrity?

I only understand assurance of integrity using a hash function. How to use cryptograpy to assure data integrity?
-1
votes
2answers
1k views

(strong) collision resistance Example

I'm studying Cryptography & Network Security. It has the following example for collision resistance: "Suppose Bob writes an IOU message, sends it to Alice, and she signs it. Bob finds two ...
3
votes
4answers
537 views

Find some hash function with deliberate collisions

I guess this should be well known (or trivially desperate), but I couldn't find any reference. I have a small number (say $k=15$) of messages $m_i$ ,$i=1\cdots k$ (they are fixed length and short, ...
1
vote
1answer
271 views

How resistant are stream ciphers like Salsa20 or ChaCha in a post-quantum world?

What kind of quantum computer would be required, if it is possible to break such ciphers?
1
vote
1answer
90 views

Can NORX be used as a general purpose hash function?

In general terms, NORX works combining a cryptographic hash function and an stream cipher. At the end of an encryption operation you end with a ciphered message plus its authenticated hash. If you ...
1
vote
1answer
104 views

Does an information-theoretically secure hash function exist?

Does an information theoretically secure hash function exist? (By exist I mean is discovered/invented and implemented, not whether it could exist.)
2
votes
2answers
88 views

Given a hash function; assuming domain % codomain = 0 and uniform collision distribution; how is entropy lost by collisions (not output truncation)?

Assuming our domain and codomain both have 4 elements, the uniform distribution of inputs to outputs means the function is injective. It is widely agreed that randomly selecting a domain element ...
0
votes
1answer
39 views

Are hashes only used to confirm data integrity when used for distributed ledgers?

I have a couple questions related to hashing and data. Please let me know if the questions I have are too broad for this site, or if clarification is needed. I have read a lot about hashing as it ...