# Questions tagged [collision-resistance]

Difficulty of finding two different inputs that hash to the same value

578 questions
Filter by
Sorted by
Tagged with
95 views

### Example of a Hash function which is second pre-image resistant but not collision resistant [duplicate]

We know that a collision resistant hash function is also second pre-image resistant. But the converse is not necessarily true. I am looking for the example of a hash function which is second pre-image ...
476 views

### What is this AES SBOX triplet property?

While playing around with the AES SBOX, I found out that there are 85 unordered triplets (a, b, c) that have the following characteristics: ...
68 views

### Are SHA-256 and SHA-512 collision resistant?

This is my first post on this forum, apologies if this post is naive. I want to learn cryptography and I want to start with this question. Context: Designing a TinyUrl system. The user inputs a ...
209 views

### Use slow hashing to reduce digest size?

I have seen this question on MD5 replacement for 128 bit digests. It is said numerous times that having a 128 bit digest is impossible today because finding a collision would only require $2^{64}$ ...
92 views

### Using date stamp down to milliseconds / ticks as a salt?

As I understand it, the salt is used to ensure that a hash of two of the same strings results in a different hash. The salt is often stored with the hash, either prepended or as a separate field. As ...
72 views

### Depth of the SHA-256 collision search knowing partial input and final hashes

So I have a partial input data (string) PART1+UNKNOWN+PART2, length of UNKNOWN is self-describing. I have a bunch of valid ...
35 views

### Finding multiple smaller collisions equal work as finding a bigger collision?

Problem A: I receive two hash digests $H(x), H(y)$ and the corresponding preimages $(x, y)$. $H$ is a 128-bit cryptographic hash function: $H: \{0,1\}^{*} \longrightarrow \{0, 1\}^{128}$ I need to ...
306 views

255 views

### Questions regarding the one-wayness and collision-resistance of a hash function based on RSA-like problem

Problem statement: "Bob is a paranoid cryptographer who does not trust dedicated hash functions such as SHA1 and SHA-2. Bob decided to build his own hash function based on some ideas from number ...
We typically model a hash function (in particular $\mathrm{SHA}$-$256$) as a function $H:\{0,1\}^{2^{64}-1} \to \{0,1\}^{256}$ with some special properties that makes them useful in practice. In this ...
Suppose we have an $n$ bit ciphertext $c$ protected by a $k$ bit $MAC$, with $k < n$. Generally, we expect collisions after $O(2^{k/2})$ ciphertext/MAC pairs are seen. Consider the following ...