Locked Everything you need to know about hashing, for beginners.

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Hashing is a fundamental concept in computer science and cryptography. It involves taking input data of any length and producing a fixed-size string of characters, typically in hexadecimal format, which represents the original data. This fixed-size string is known as the hash value or hash code. The process of converting data into a hash is done using a specific mathematical algorithm called a hash function.

 

Here's everything you need to know about hashing:

 

Purpose of Hashing:

 

Data Integrity: Hashing is commonly used to verify data integrity. By comparing the hash values of the original data and the received data, one can determine if the data has been altered or corrupted during transmission.

Data Retrieval: Hashes are often used as keys in data structures like hash tables, which enable efficient data retrieval based on the hash value.

Hash Functions:

 

A hash function is a deterministic algorithm that takes an input (or "message") and produces a fixed-size string, the hash value.

The ideal hash function should be fast to compute, produce a unique hash value for each unique input, and be resistant to collisions (two different inputs producing the same hash value).

Hash Collisions:

 

A collision occurs when two different inputs produce the same hash value.

While it's essential for a hash function to minimize collisions, it is practically impossible to eliminate them entirely due to the pigeonhole principle, where more possible inputs than possible hash values exist.

Cryptographically secure hash functions aim to make finding collisions computationally infeasible.

Hashing Algorithms:

 

There are many popular hashing algorithms, each designed for specific purposes:

MD5 (Message Digest Algorithm 5): Not recommended for cryptographic use due to vulnerabilities.

SHA-1 (Secure Hash Algorithm 1): Deprecated for cryptographic use due to vulnerabilities.

SHA-256, SHA-384, and SHA-512: Part of the SHA-2 family, considered secure for most cryptographic purposes.

SHA-3: The latest member of the SHA family, designed as a replacement for SHA-2.

Applications of Hashing:

 

Password Storage: Hashing is widely used for securely storing passwords. Instead of storing plain text passwords, systems store their hashes. When a user tries to log in, the system hashes the entered password and compares it with the stored hash.

Digital Signatures: In public-key cryptography, hashing is used to generate a digest of a message that is then signed with a private key to produce a digital signature.

Data Structures: Hash tables and hash maps use hash codes to efficiently store and retrieve data.

Blockchain Technology: Hashing plays a critical role in creating blocks and linking them in a blockchain network.

Salting:

 

To improve the security of password hashing, a technique called "salting" is used. A random value (salt) is generated and combined with the password before hashing.

Salting prevents attackers from using precomputed tables (rainbow tables) to reverse-engineer the original passwords from their hashes, as each password will have a unique salt.

Security Considerations:

 

For cryptographic purposes, it is crucial to use a cryptographically secure hash function that is currently considered resistant to attacks.

The security of hashing also depends on the proper management of salts, keys, and the implementation of the hashing algorithm.

In conclusion, hashing is a versatile concept used for data integrity verification, data retrieval, and secure storage of passwords and other sensitive information. It is essential to use modern, cryptographically secure hash functions and follow best practices to ensure the integrity and security of hashed data.