Or if you want to use the key in same application click Apply in the Actions pane and the machine key will be updated in web.config.
<machineKey validationKey="883A787F3B793567817EA540DCA4285B1A695C58A38B3493E1E69821148E5E6B5032F61813DF81B9731AB5F8AF7ECA3A75429E38D6513408E86ED4AC77243439" decryptionKey="7F0884CE1698D23538D4FC3670FD122FCF856645518617B7" validation="SHA1" decryption="Auto"/>
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