I'm an engineer with experience in applied cryptography, in particular in Smart Card systems.
Feel free to edit my answers to fix obvious errors, or improve them on expression (I'm not a native English speaker).
69 How big an RSA key is considered secure today? Mar 3 '12
33 Why can't I reverse a hash to a possible input? Nov 11 '15
28 Impacts of not using RSA exponent of 65537 Jul 1 '12
27 What security authorities and standards reject $e=3$ in RSA, when, and with what rationale? May 25 '13
21 Is TrueCrypt's multiple/cascading encryption safe? Feb 27 '13
20 How secure would HMAC-SHA3 be? Apr 24 '14