Hashing

Hashing is the process of converting an input of any length into a fixed-size string of text using a mathematical function. This output is called a 'hash value' or 'digest'. Unlike encryption, hashing is a one-way process, meaning you cannot reverse the hash value to get back the original input. This one-way property is crucial for its security applications. A good cryptographic hash function has three key properties: 1. It's deterministic, meaning the same input will always produce the same output. 2. It's fast to compute the hash value for any given message. 3. It's infeasible to generate a message from its hash value (pre-image resistance) and infeasible to find two different messages with the same hash (collision resistance). One of the most common uses for hashing is password storage. When you create a password for an account, the service doesn't store your actual password. Instead, it runs your password through a hash function and stores the resulting hash. When you log in, the service hashes the password you entered and compares it to the stored hash. If they match, you're authenticated. This way, even if a company's database is breached, the attackers only get a list of hashes, not the actual passwords. Hashing is also used to ensure data integrity. Before sending a file, you can compute its hash value. The recipient can then compute the hash of the file they received. If the two hashes match, it proves that the file was not altered during transmission. Common hashing algorithms include SHA-256 (Secure Hash Algorithm 256-bit) and MD5 (Message Digest 5, which is now considered insecure and should not be used for security purposes).