identify and describe three types of cryptography?

Discuss at least two (2) topics from this course that you found the most beneficial.  How will you use this information in your professional career? You do not have to document your sources for this question, unless you use quoted material.  This is an opinion question. At least one peer reply is still required.       

Topics : security issues associated with email?

identify and describe three types of cryptography?

need 300 words