After yesterdays first signed PSP homebrew bbtgp has released PrxEncrypter. Its a tool that can sign any homebrew. Its has already been tested to sign a simple hello world that worked on the PSP fat, Slim and Bright. This is for user mode only homebrew at this stage. So no signing ISO loaders or Custom Firmware.
modded build.mak and included sample. Set ENCRYPT=1 in the makefile for other programs to encrypt them