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OAuth, or Open Authorization, is an open standard authorization protocol for access delegation. It is a secure method to allow users to grant service providers (i.e., websites and applications) access to their information without giving them their passwords.

OAuth provides clients with secure delegated access to server resources on behalf of the server owner. Specific authorization flows enable the client to access protected resources without having to provide their password. Instead, the client uses access tokens that can be approved by the resource owner to grant them access to that resource.

What are OAuth tokens?

OAuth tokens authorize a user’s access to resources. In other words, they do not authenticate users, but are used by the service provider to authorize access on behalf of the user to other resources.

An OAuth transaction occurs when a user requests permission from another resource using their service provider identity. The resource will request permission from the service provider, which is given in the form of a request token and a secret. Next, the resource redirects the user to their service provider to authenticate the request. At this point, the resource exchanges the request token for an access token and a secret. If the two tokens share the same secret, the OAuth process is complete, and the user has successfully delegated access for the resource to the service provider.

The OAuth Process

The above example summarizes a general OAuth process. OAuth also allows more granular control and permissions, such as the right to revoke tokens whenever the user wants and defining different levels of access to service providers for different resources.

OAuth 1.0 vs. OAuth 2.0

In 2012, OAuth 2.0 was introduced as a major overhaul to OAuth 1.0. The changes made to this version of OAuth were significant enough that versions 2.0 and 1.0 are not compatible. OAuth 2.0 was designed to address a session fixation security flaw in the OAuth authorization flow.

Although this issue has been resolved with OAuth 2.0, the new version intentionally does not define or support encryption, signature, client verification, or channel binding, but instead requires that implementers use a different security protocol like HTTPS/TLS for that purpose.

The differences between OAuth 1.0 and 2.0 can are summarized below:

OAuth 1.0 vs OAuth 2.0

OAuth vs. SAML – what’s the difference?

SAML is an XML variant language that describes a framework that allows one device to perform both authentication and authorization on behalf of one or more devices.

As light-weight options for encoding data emerged, such as JSON, OAuth gained adoption to support mobile device users. Although OAuth is a newer protocol that evolved from a need to replace SAML, both protocols are critical for secure single sign-on (SSO).

In other words, OAuth is not an alternative to SAML as much as the two protocols can complement each other. For example, in an SSO environment, SAML may be responsible for authentication (confirming the user is authentic and should be granted access) and OAuth will be responsible for authorization (granting access to specific protected resources).

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