Based on http://www.nilsschneider.net/2013/01/28/recovering-bitcoin-private-keys.html
Regarding Bitcoin Tx:
https://blockchain.info/tx/9ec4bc49e828d924af1d1029cacf709431abbde46d59554b62bc270e3b29c4b1.
As it's said in the previous article you need to poke around into the OP_CHECKSIG 
function in order to get z1 and z2,
In other hand for every other parameters you should be able to get them from the Tx itself.

Q=dP compute public key Q where d is a secret scalar and G the base point
(x1,y1)=kP where k is random choosen an secret
r= x1 mod n
compute k**-1 or inv(k)
compute z=hash(m)
s= inv(k)(z + d) mod n
sig=k(r,s) or (r,-s mod n)
Key recovery
d = (sk-z)/r where r is the same 

python ProofOfConcept.py