What technique is used to secure passwords by converting them into unreadable strings?

Hashing is a technique used to secure passwords by converting them into fixed-size strings of characters that are unreadable and are typically represented in hexadecimal format. When a password is hashed, it undergoes a one-way transformation that creates a unique hash value based on the input data, which means the original password cannot easily be retrieved or reconstructed from the hash.

Hashing is integral to data integrity and authentication. When a user creates an account or changes their password, the system hashes the password and stores the resulting hash value rather than the plaintext password. When the user logs in, the system hashes the provided password again and compares it to the stored hash. If the hashes match, access is granted, ensuring that even if the database is compromised, the actual passwords remain secure.

This method differs fundamentally from encoding, which is designed to be reversible, allowing the original data to be returned, and encryption, which also aims to protect confidentiality but can be reversed with the appropriate key. Compression, on the other hand, reduces the size of data but does not secure it. Therefore, hashing stands out as the effective technique for securing passwords by rendering them into unreadable and non-reversible strings.