How is data compliance checked after login and password input?

Verification of data after entering login and password usually occurs as follows:

1. The user enters login and password.
2. The application receives this data and searches for the user in the database by login.
3. If the user is found, the entered password is compared with the stored password.

Important: passwords in the database are usually stored as hashes (for example, using bcrypt, PBKDF2, Argon2 algorithms). Therefore, the check proceeds as follows:

• The entered password is hashed with the same algorithm and parameters.
• The resulting hash is compared with the stored hash.

If the hashes match — the user is authenticated.

Example in Java (simplified):

String inputPassword = ...; // password entered by the user
String storedHash = getPasswordHashFromDB(login);

boolean matches = PasswordHasher.verify(inputPassword, storedHash);
if (matches) {
    // successful login
} else {
    // authentication error
}

Where PasswordHasher.verify is a method that implements password verification considering salt and hashing algorithm.