What is a .LASTLOGIN file?
The .LASTLOGIN file is a special kind of file for Minecraft players. It's like a secret box that keeps the name and secret code (username and password) of the person who last used the Minecraft game launcher. You can find this file in a specific place on your computer, which is C/Users/User/AppData/Roaming/minecraft.
Even though it's about keeping secrets, this file is usually locked up using a special way of encoding called DES in CBC mode with PKCS #5 padding. This is like putting your secret in a safe so only you and the game can know it. But, if the Java on your computer doesn't know how to use this safe, then your name and secret code are just left out without any protection. Also, if you told the launcher you don't want it to remember your secret code, then that part is left empty in the .LASTLOGIN file.
If you're curious and want to peek inside this file, you can use simple programs like Notepad on Windows or TextEdit on Mac. These programs let you open and look at the file, but remember, because it's usually encoded, what you see might look like a bunch of jumbled-up letters and numbers instead of your actual username and password.
Verification
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