Mr. Back -

A mini web series by Certified Rascals that follows the workplace chaos caused by an overzealous backup manager named Naresh.

Under his new name, Choi Shin-hyung, he experiences love for the first time with a young part-timer, Eun Ha-soo, and attempts to reconcile with his estranged son. Mr. Back

The name is also used for smaller web-based projects and social media personas: A mini web series by Certified Rascals that

A rapper who released the song "Yeah (Mr. Back Again)" . Mr. Back

The most common reference is the 16-episode MBC TV series starring Shin Ha-kyun and Jang Na-ra.

He is the creator of Hashcash , a proof-of-work system cited in the original Bitcoin whitepaper by Satoshi Nakamoto.