Why does hashing prevent hackers from stealing the contents of a password file?

Hashing is a one-way cryptographic function that transforms input data, such as passwords, into a fixed-size string of characters, which is typically a sequence of digits and letters. The key feature of hashing is that it is designed to be irreversible; this means that the original password cannot be easily reconstructed from its hash value.

When a password is hashed, even a slight change in the input will produce a drastically different hash output, providing a level of obscurity and security. Since hashes do not contain any information about the original input, they cannot be decrypted or reversed into the original password, thus minimizing the risk of exposure if a password file is compromised. Consequently, when hackers gain access to a password file containing only the hashed values of passwords, they encounter significant challenges in determining the actual passwords.

This process ensures that, even if hackers steal the data, they cannot directly access or retrieve the stored passwords, as they would be faced with the daunting task of attempting to crack the hash – typically through methods like brute force or rainbow tables – which is often computationally expensive and time-consuming.