fft - Echo hiding technique

I'm trying to figure out how to use DSP techniques in order to both add artificial echoes to a sound file, but more importantly to be able to detect these echoes. I've been reading about it here: http://www.snotmonkey.com/work/school/405/methods.html#echo

Can someone point me to possibly some example code using Apple's Accelerate framework for being able to detect hidden echoes in sound coming from the microphone? Also, for detecting the echoes, it is important that the application doesn't need to have knowledge of the original sound, meaning it should be detectable in any sound that's being played that has these echoes.

Thank you for any information.