Martii Malmi, an early contributor to Bitcoin, gained attention for sharing his email correspondence with Bitcoin creator Satoshi Nakamoto. However, Malmi's involvement extends beyond emails; he was one of the first developers to work on Bitcoin's code alongside its pseudonymous creator, as documented by Peter Rizzo.

Between 2009 and 2011, Malmi contributed to Bitcoin's development, collaborating with prominent figures like Hal Finney, Gavin Andresen, and Laszlo Hanyecz, known for purchasing pizza with Bitcoin on Bitcoin Pizza Day.

During his college years, Malmi defended Bitcoin ideologically, advocating for the separation of money and state on anti-state.org. He also refuted claims that Bitcoin lacked intrinsic value.

Malmi authored much of the content on Bitcoin.org, the cryptocurrency's first website, and was the sole developer to work on version 0.2 of the Bitcoin Core software alongside Nakamoto.

In 2009, Malmi completed one of the earliest Bitcoin-to-USD trades, selling 5000 BTC for $5. He later established the first Bitcoin exchange with Nakamoto's support in 2010, using 30,000 of his own BTC as the sole market maker. This exchange facilitated the onboarding of hundreds of users to Bitcoin.

In 2011, Malmi purchased an apartment using 10,000 BTC when Bitcoin was trading at around $30, marking one of the earliest major real-world transactions with Bitcoin.

Records indicate that Malmi has contributed roughly 55,000 BTC over the years to support the ecosystem, which would be valued at over $3 billion today. Despite his substantial Bitcoin holdings, he publicly stated in 2020 that he puts most of his savings into Bitcoin, describing his holdings at that time as "not much."

Currently, Malmi serves as the CEO of Sirius Business, a company focusing on decentralized social media.

Recent developments, particularly involving computer scientist Craig Wright's claims to be Bitcoin's creator, prompted Malmi to discuss his collaboration with Nakamoto. In a lawsuit with the Crypto Open Patent Alliance (COPA), Wright mentioned Malmi as the creator of the dark web market Silk Road, an allegation Malmi denies and has never been criminally accused of. Malmi has joined COPA's efforts to refute Wright's claims, providing testimony and submitting his emails with Nakamoto as evidence, shedding light on Bitcoin's early days and revealing inconsistencies in Wright's assertions.