Files ending with KEYCHAIN are generated by Apple Keychain. Keychain is a password management utility that stores the authentication information and is included with Mac OSX. Keychain files contain an encrypted collection of sensitive user authentication data such as passwords, certificates, and private keys.
Keychain files automatically authenticate the user once the option to remember the authentication information has been selected. They are used, among other things, to log the user in on websites or to gain network access.
Example for KEYCHAIN files are the login.Keychain or system.Keychain. Keychain files are usually located in the system folder / library / keychains or in the local folder user / library / keychains.
Most often resolving problems with opening KEYCHAIN files is very simple. Just install an appropriate program that supports such files. All of the listed programs support KEYCHAIN files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of KEYCHAIN files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate KEYCHAIN files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the Apple Keychain Access applications is not on the list, select "Browse" option in order to manually locate the directory where Apple Keychain Access has been installed.
Sometimes problems with opening KEYCHAIN files may not lie with the application itself, but can arise due to other causes, such as: