The OAuth 2 specification
There is sometimes a misconception that OAuth 2 is an evolution from OAuth 1, but it is a completely different approach. OAuth 1 specification requires signatures, so you would have to use cryptographic algorithms to create generate and validate those signatures that are no longer required for OAuth 2. The OAuth 2 encryption is now handled by TLS, which is required.
Important note
OAuth 2 RFC-6749, The OAuth 2.0 Authorization Framework (https://tools.ietf.org/html/rfc6749):
The OAuth 2.0 authorization framework enables a third-party application to obtain limited access to an HTTP service, either on behalf of a resource owner by orchestrating an approval interaction between the resource owner and the HTTP service, or by allowing the third-party application to obtain access on its own behalf.
This specification replaces and makes obsolete the OAuth 1.0 protocol described in RFC 5849, The OAuth 1.0 Protocol (https://tools.ietf.org/html/rfc5849).
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