The info dictionary in your example starts at
infod13:
You must determine the info data and calculate the SHA1 of the info data. After that you must to URL encode the SHA1.
info_hash: urlencoded 20-byte SHA1 hash of the value of the info key from the Metainfo file. Note that the value will be a bencoded dictionary, given the definition of the info key above.
There is an example written in Qt which i think it might help you. (Qt5.2.1/5.2.1/gcc_64/examples/network/torrent) You can find it online here qt torrent
Edit: Here is a good answer for what you are looking for Calculating the info-hash of a torrent file