api - Authenticating Requests From A Single Server -

i'm working on project contains data belonging multiple clients, , i'm trying find secure way notify servers of sensitive changes data.

the issue secure method found oauth, since server pushing updates them, mean each client have implement oauth provider solely authenticate server, , feels bit of overkill.

my question is: keeping in mind not clients use https, enough use shared secret, timestamp, , form of encryption servers safely receive , validate updates or leave them vulnerable attacks?

yes, secure. simple messages think jtw choice. use authentication or actual notification itself. few reasons might want use it:

• it's signed, know message hasn't been tampered with.
• you can encrypt public/private key pairs.
• you can add data like.
• it's simple implement , doesn't require back-and forth exchange between servers oauth does.