Attacks & Hash function vulnerabilities

In the context of computer science and cryptography, a hash function is a mathematical algorithm that takes an input (the „message“) and produces a fixed-size string of characters, which is typically a hash value or digest. The primary purpose of a hash function is to ensure data integrity and provide a unique representation of the input data.

An attack on a hash function refers to any attempt to exploit weaknesses or vulnerabilities in the algorithm to achieve a specific goal. The goals of such attacks can vary depending on the context and the attacker’s objectives. Here are a few common types of attacks and vulnerabilities related to hash functions:

Length Extention Attack: Some hash functions, particularly those based on the Merkle-Damgård construction, are vulnerable to length extension attacks. In this type of attack, the attacker takes an existing hash and a known part of the original message to extend the hash function’s output without knowing the complete message. This vulnerability can lead to the creation of maliciously crafted messages that appear legitimate to the system.

Collision Attack: A collision occurs when two different inputs produce the same hash value. In a collision attack, the attacker tries to find two inputs that generate an identical hash value. The objective may be to undermine the integrity of the hash function, break digital signatures, or compromise other cryptographic systems reliant on hash functions.

PreImage-Attack: In a preimage attack, the attacker tries to find a message that matches a specific hash value. The objective is to reverse-engineer the original input from its hash. A successful preimage attack allows an attacker to violate the one-way property of a hash function, potentially compromising data confidentiality or authentication mechanisms.

Birthday Attack: The birthday paradox states that in a set of just 23 people, the probability of two people sharing the same birthday exceeds 50%. Similarly, a birthday attack leverages the same principle to find collisions in a hash function more efficiently than a straightforward collision attack. By exploiting the probability of collisions in a hash function, attackers can reduce the time and computational effort required to find collisions.