What is a Hash Function?
A hash function is a mathematical algorithm that transforms input data of any size into a fixed-size string of text, typically a sequence of numbers and letters. In the context of web security, it is used to ensure data integrity and secure sensitive information, such as passwords and transactions.
How Hash Functions Work
When data is input into a hash function, it processes the data through a series of computations to produce a unique hash value, also known as a digest. Even the slightest change in the input data will result in a significantly different hash output. This property is known as the avalanche effect.
Common Uses in Web Security
- Password Storage: Instead of saving passwords in plaintext, systems store the hashed version. When a user logs in, the input password is hashed and compared with the stored hash.
- Data Integrity: Hash functions ensure that data has not been altered during transmission or storage. Any change would result in a different hash value, alerting users to potential tampering.
- Digital Signatures: Hash functions are used in conjunction with public key cryptography to verify the authenticity and integrity of messages.
Examples of Hash Functions
Some widely-used hash functions include MD5, SHA-1, and SHA-256. While MD5 and SHA-1 are considered less secure due to vulnerabilities, SHA-256 is part of the SHA-2 family and is currently recommended for secure applications.