Mathematicians are not inherently good cryptographers as it is another field of study entirely, requiring thorough knowledge of both
Examination of the Telegram chat client is a good case study.
They have utilized a homemade encryption, which poses risks
An excellent thread on this topic is available at stackexchange, up-to-date response to this inital query has been posted as of may 16:
http://security.stackexchange.com/questions/49782/is-telegram-secure
(Older, but included as reference) https://unhandledexpression.com/2013/12/17/telegram-stand-back-we-know-maths/
(2015 post) https://medium.com/@thegrugq/operational-telegram-cbbaadb9013a#.gb7od1j6i
here is a paper demonstrating that MTProto is not IND-CCA secure
https://eprint.iacr.org/2015/1177.pdf
not if it has a backdoor.... there is always danger NSA has an entry point on demand.. and no one can compete with their mathematics talent pool... its a challenge for sure.. so when you say cook something inside.. maybe simpler is better..
Why yes, yes it is 
Examination of the Telegram chat client is a good case study.
They have utilized a homemade encryption, which poses risks
An excellent thread on this topic is available at stackexchange, up-to-date response to this inital query has been posted as of may 16:
http://security.stackexchange.com/questions/49782/is-telegram-secure
(Older, but included as reference) https://unhandledexpression.com/2013/12/17/telegram-stand-back-we-know-maths/
(2015 post) https://medium.com/@thegrugq/operational-telegram-cbbaadb9013a#.gb7od1j6i
here is a paper demonstrating that MTProto is not IND-CCA secure
https://eprint.iacr.org/2015/1177.pdf
not if it has a backdoor.... there is always danger NSA has an entry point on demand.. and no one can compete with their mathematics talent pool... its a challenge for sure.. so when you say cook something inside.. maybe simpler is better..