1)钥匙串存储在iOS定义位置的沙箱外部.这是为了防止越狱的设备访问它.通过文件系统不可见.钥匙串与Mac OS X相同，只是苹果公司认为没有必要让最终用户访问它.您只能通过已定义的API与它进行交互.我应该注意，即使使用越狱设备，似乎也无法实现阻止访问的目的.

1) The keychain is stored outside the sandbox in an iOS defined location. This is to prevent jailbroken devices from getting access to it. It is not visible through the filesystem. The keychain is the same as Mac OS X, except Apple felt that it wasn't necessary to give end users access to it. You cannot interact with it except through the defined APIs. I should note that it doesn't seem to be accomplishing the goal of preventing access even with jailbroken devices.

2)除了存储用户名和密码外，我真的不知道钥匙串的实际用法.

2) I don't really know about practical usage of the keychain outside of storing usernames and passwords.