A typical web app is mostly stateless, because of its request/response nature. The HTTP protocol is the best example of a stateless protocol. But since most web apps need state, in order to hold the state between server and client, cookies are used such that the server can send a cookie in every response back to the client. This means the next request made from the client will include this cookie and will thus be recognized by the server. This way the server can maintain a session with the stateless client, knowing mostly everything about the app's state, but stored in the server. In this scenario at no moment does the client hold state, which is not how Ember.js works.

在Ember.js中情况有所不同。Ember.js使程序员的工作变得更容易，因为它确实在客户端为您保存了状态，可以随时了解其状态，而不必向服务器请求状态数据。

然而，在客户端保存状态有时也会引入在无状态情况下不存在的并发问题。然而，Ember.js也为您处理这些问题;具体地说，ember-data是基于这一点构建的。总之，Ember.js是为有状态客户端设计的框架。

Ember.js不像典型的无状态web应用程序那样，会话、状态和相应的cookie几乎完全由服务器处理。Ember.js将其状态完全保存在Javascript中(在客户端的内存中，而不是像其他框架那样在DOM中)，并且不需要服务器来管理会话。这导致Ember.js在许多情况下更加通用，例如当你的应用程序处于离线模式时。

显然，出于安全原因，每次发出请求时都需要向服务器发送某种令牌或唯一密钥，以便进行身份验证。通过这种方式，服务器可以查找发送令牌(最初由服务器发出)，并在将响应发送回客户端之前验证它是否有效。

在我看来，使用认证令牌而不是在Ember Auth FAQ中所述的cookie的主要原因是Ember.js框架的性质，也因为它更适合有状态的web应用程序范例。因此，cookie机制并不是构建Ember.js应用程序的最佳方法。

我希望我的回答能让你的问题更有意义。

基于令牌的认证是无状态的，服务器不需要在会话中存储用户信息。这样就可以扩展应用程序，而不用担心用户已经登录到哪里。有web服务器框架的亲缘性基于cookie，而这不是一个问题，基于令牌。因此，可以使用相同的令牌从我们登录的域以外的域获取安全资源，从而避免了另一个uid/pwd身份验证。

非常好的文章:

http://www.toptal.com/web/cookie-free-authentication-with-json-web-tokens-an-example-in-laravel-and-angularjs

Tokens need to be stored somewhere (local/session storage or cookies) Tokens can expire like cookies, but you have more control Local/session storage won't work across domains, use a marker cookie Preflight requests will be sent on each CORS request When you need to stream something, use the token to get a signed request It's easier to deal with XSS than XSRF The token gets sent on every request, watch out its size If you store confidential info, encrypt the token JSON Web Tokens can be used in OAuth Tokens are not silver bullets, think about your authorization use cases carefully

http://blog.auth0.com/2014/01/27/ten-things-you-should-know-about-tokens-and-cookies/

http://blog.auth0.com/2014/01/07/angularjs-authentication-with-cookies-vs-token/

使用Token时…

需要联邦。例如，您希望使用一个提供者(令牌分发器)作为令牌颁发者，然后使用api服务器作为令牌验证器。应用程序可以向令牌分发器进行身份验证，接收令牌，然后将该令牌提交给api服务器进行验证。(同样适用于谷歌登录。或贝宝。或Salesforce.com。等)

Asynchrony is required. For example, you want the client to send in a request, and then store that request somewhere, to be acted on by a separate system "later". That separate system will not have a synchronous connection to the client, and it may not have a direct connection to a central token dispensary. a JWT can be read by the asynchronous processing system to determine whether the work item can and should be fulfilled at that later time. This is, in a way, related to the Federation idea above. Be careful here, though: JWT expire. If the queue holding the work item does not get processed within the lifetime of the JWT, then the claims should no longer be trusted.

客户需要签署请求。在这里，请求由客户端使用他的私钥签署，服务器将使用客户端已经注册的公钥进行验证。

简而言之:

JWT vs Cookie Auth

|                    | Cookie        | JWT                             |
| Stateless          | No            | Yes                             |
| Cross domain usage | No            | Yes                             |
| Mobile ready       | No            | Yes                             |
| Performance        | Low           | High (no need in request to DB) |
| Add to request     | Automatically | Manually (if not in cookie)     |

一个主要的区别是cookie服从同源策略，而令牌则不是。这就产生了各种各样的下游效应。

由于cookie只发送给特定的主机，该主机必须承担验证用户身份的责任，用户必须在该主机上创建一个具有安全数据的帐户，以便进行验证。

Tokens on the other hand are issued and are not subject to same origin policy. The issuer can be literally anybody and it is up to the host to decide which issuers to trust. An issuer like Google and Facebook is typically well trusted so a host can shift the burden of authenticating the user (including storing all user security data) to another party and the user can consolidate their personal data under a specific issuer and not have to remember a bunch of different passwords for each host they interact with.

这允许单点登录场景，从而减少用户体验中的整体摩擦。从理论上讲，网络也变得更加安全，因为专门的身份提供者出现了，提供认证服务，而不是每个ma和pa网站都有自己的，可能不成熟的认证系统。随着这些提供商的出现，为非常基本的资源提供安全网络资源的成本也趋向于零。

因此，总的来说，令牌减少了与提供身份验证相关的摩擦和成本，并将安全web各个方面的负担转移到能够更好地实现和维护安全系统的中心化方。