| CPC H04L 63/0807 (2013.01) [G06F 21/6245 (2013.01); H04L 63/0407 (2013.01); H04W 4/12 (2013.01)] | 60 Claims | 

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               1. A method comprising: 
            sending, to a user device, based on a received valid refresh token, an invalid access token; 
                receiving, via the user device, based on a failed attempt to access a resource with the invalid access token, a valid refresh token; and 
                sending, to the user device, based on the valid refresh token, a valid access token. 
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