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I'd like to know about login processing of linux based os.

In ubuntu, you can log in in a very short time by entering the correct password on the login screen. Where do you keep your username and password information?

If i run cat/etc/shadow as the root user, the user name and the encrypted password are displayed. However, it is an encrypted password, and it is quite a resource to decrypt the encrypted password. I think that is necessary.

If the password that matches the user name entered by the user is obtained from/etc/shadow, decrypted, and compared with the entered password, it will take a considerable amount of time to process login success. .

I'd like you to know if you have user name and password information and what kind of processing you can log in in such a short time.

I'd like you to tell me about a site that contains information related to this answer. (I didn't find it myself)

  • Answer # 1

      

    Where do you keep your username and password information?

    Normally a file (/etc/passwd/etc/shadow). If set, it is possible to authenticate by referring to the information of the external authentication server.

      

    I think it takes a lot of resources to decrypt the encrypted password.

    Do not decipher.
    It is OK if the password entered by the user is obtained using a hashing function to obtain a hash value and matches the hash value written in/etc/shadow.

  • Answer # 2

      

    I think it takes a lot of resources to decrypt the encrypted password.

    Decryption isnotpractical. The input password is hashed using the same method (and salt), and it is judged whether the results match.