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Keychain password ***** ***** as your login or administrator password ***** iCloud/Apple ID password. So enter those passwords (try leaving it blank and press OK as well).. If that didn't work or if you are getting that keychain pop up frequently, then you have to reset Keychain database.
So go to Apple menu > System Preferences. In System Preferences, click iCloud. In iCloud, scroll down and turn off Keychain from the list of options if it is enabled.
Then in Finder, hold down Option key, click on Go menu and select Library. From the resulting Library folder, trash the Keychain folder (Don't empty the Trash). Then restart your Mac. This will fix it.
Please let me know if that didn't work, so we can continue troubleshooting