How do passwords and usernames work and how are they encrypted?

Answer 1

A username is an account set up by a computer administrator. An administrator has full access of the data stored and can do such things as add or remove software. A username is good because it allows multiple people to use the same computer but at the same time restricting access if desired. Passwords are group of characters that are encrypted to prevent or slow down access to unwanted users. Most PC user do not have the software like ophcrack to hack and obtain passwords.

Answer 2

Passwords work by maintaining a list of users along with their passwords. To gain entry you must enter the username and the password that corresponds with that username. Usernames and password are typically case-sensitive, so "THIS" is not the same as "this".

However, the password list cannot be stored as a plain text list of usernames and passwords because anyone who gains entry to the system can read the file and thus determine all the passwords for all the users. Nor can we simply encrypt the list because anything that can be encrypted can also be decrypted. We solve the problem by using a hash function. A hash function is a one-way function. When we pass an argument (the password) to a hash function we generate a hash value. Even if we know which specific hash function generated that hash value, it is nigh-on impossible to determine what the original argument was without trying and testing every permutation. Knowing the length would narrow the search down somewhat, but even an 8 character password has 62^8 permutations (assuming uppercase, lowercase and digital characters only), which is more than 218 trillion permutations!