Final answer:
The central idea of the paragraph is that breaking the RSA cipher is the greatest challenge for cryptanalysts.
Step-by-step explanation:
The central idea of this paragraph is that breaking the RSA cipher is the greatest challenge for cryptanalysts. The RSA cipher is used to protect important military, diplomatic, commercial, and criminal communications, which makes it a prime target for intelligence gathering organizations. Cryptanalysts recognize that in order to challenge strong RSA encryption, they will need to make a major theoretical or technological breakthrough.