Depends on what level of understanding is required. There is definitely the scientific level that is mentioned in this question, but there is also understanding the risks, management, application of encryption. Often the risks, management and application of encryption can be more challenging than the scientific and algorithm development. That is because these topics involve multiple parties such as the user interface and the management of an encryption system. That would be the user and IT… and then don’t forget the accountants who want you to justify the costs of any particular encryption system.
Managing a secure connection to a website is one thing using SSL certificates but managing endpoint encryption on mobile devices is entirely different. Key management, encryption standards, and user interaction are all elements no matter the purpose of encryption.