There are two options for authentication, both require you to store data locally that you must be able to pull out as plain text (I.E., you can not use a base encoding that is not decodable):
OAuth Authentication - You would need to store the Username and the Access Token. Any type of secure database that is encrypted will be more than secure enough for this information as it is actually useless without your private consumer key token to combine with (which should also be securely stored seperately).
Basic Authentication - You would need to store the Username and Password. You will want to make sure this is stored in a very secure database as this allows access to the account fully from any source, including our web based UI. Again though, any secure database generally has enough security, provide you keep up to date with your patches, to ensure that all reasonable security expectations are met. You again must use a security system that can be decoded, you could not store this information as Base64 encoded for example, as you must be able to create the requests using this information as plain text.
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