SKFU has made available a PS Vita .PKG xTractor version 1.00 homebrew application for developers.

This program can decrypt & extract PS VITA game package (.pkg) files.

To use the program you need to place the PS VITA .pkg AES key in the same dir as the executable. Funny as SONY is, they probably were to lazy to think of a new key and just used *hehe*, the PSP .pkg AES key.

Information tab not finished, yet. It will be completed in next version. So just put the PSP .pkg AES key in hex syntax in aes.key file in the same folder and you are ready to go.

Download PS Vita .PKG xTractor
Source- SKFU's Blog: PS VITA .pkg xTractor 1.00