How to Prevent Birthday Attacks?
Tags: birthdayattacks, cybersecurity, collisionattack, infosectrain
Published: 2023-08-25 08:53:05



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## **Overview of Birthday Attack**
The term "birthday attack" can also refer to a collision attack or a type of brute force attack in cryptography. This attack aims to find a collision in a hash function by systematically generating and comparing a large number of inputs to look for two inputs that generate the same hash value. The attack takes advantage of the birthday paradox, which states that the probability of two people having the same birthday increases as the number of people increases.


## **How Does a Birthday Attack Work?**
Primarily, the birthday attack targets the hash function to find two inputs with the same hash value. Below is a step-by-step approach that defines how the birthday attack in cryptography works :

• The attacker starts by selecting a hash function they want to target.  
• The attacker systematically generates random inputs and calculates their hash codes using the selected hash function.
• As the attacker generates more inputs, the probability of finding a collision increases due to the birthday paradox.
The general formula to calculate the probability of a collision in the birthday attack is:

P(collision) = 1 - (365! / (365^n * (365 - n)!))

Where n represents the number of inputs (or hash values) generated and ‘!’ denotes the factorial operator.

• The attacker stores each generated input along with its corresponding hash code.
• The attacker continues generating inputs and calculating their hash codes until they find a collision.  
• Once the attacker finds a collision, they can use it to potentially exploit vulnerabilities in systems that rely on the hash function. For example, if the hash function is used for digital signatures or password storage, the attacker may be able to create fraudulent signatures or modify data without detection.

## **How Do You Prevent Birthday Attacks?**
To prevent birthday attacks, consider the following measures:

**• Use secure hash functions with large hash code length:** Implement secure cryptographic hash functions with sufficiently large hash code sizes, such as SHA-256, to expand the code space and minimize the probability of collisions.
**• Implement salted hashing**: Add a unique random value, called a salt, to each input before hashing, making precomputed hash tables less effective.
**• Regularly update hash algorithms:** Keep up-to-date with the latest hash functions and cryptographic algorithms, as older algorithms may have vulnerabilities.
**• Stay informed:** Stay updated with the latest advancements and research in cryptography to address any vulnerabilities that may arise.
**• Implement proper key management:** In addition to hash function security, it is crucial to implement proper key management practices, including the secure storage and handling of cryptographic keys.

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