Intro
Hal Finney is a hero of mine for a number of reasons. One of his direct contributions is RPOW which stands for Reusable Proof of Work. RPOW uses Hash Cash developed by Adam Back, the Proof-of-Work mechanism of Bitcoin, to make tokens for Proof-of-Work reusable without what's called double-spending. Double-spending would essentially allow someone to spend a token twice, for instance Bitcoin, making it's scarcity or relevance not valuable. Hash Cash's original functionality was to help combat mailing list spam. Without their great contributions the evolution of technology to create the first popular blockchain, the Bitcoin Blockchain, may have taken much longer.

How this relates to Steemit.com
Steemit.com runs on the Steem Blockchain. Almost everything we do is cryptographically secured in a Blockchain. Instead of the proof-of-work that Bitcoin uses which is computational power of the SHA-256 algorithm, it uses DPoS or delegated proof-of-stake. Created primarily by Dan Larimer, it has similar structure to that of Bitshares, a secure decentralized exchange which allows you to maintain ownership, unlike centralized exchanges like Bitfinex. Steem relies on witnesses which are delegated individuals who are able to quickly agree on blocks, and add them to the Steem Chain. You can vote for your favorite witness @ https://steemit.com/~witnesses. Creations like Bitshares and the following Steem project are still foundation-ally Blockchains and evolved out of the creations of work from Hal Finney and others.

Hal Finney's Impact on Privacy
Hal Finney wrote much of the early code for PGP (pretty good privacy), along with Phil Zimmerman. He was the first hire of the PGP corporation. He also founded the first cryptographically anonymous remailer allowing people to contribute to cypherpunk discussions and communicate with others around the world with anonymity. PGP allows you to encrypt emails with a private key. Essentially only you and your desired recipients can read the contents. Funny enough when the technology became popular the PGP corporation was sued, "Shortly after its release, PGP encryption found its way outside the United States, and in February 1993 Zimmermann became the formal target of a criminal investigation by the US Government for "munitions export without a license". This might give some insight as to why someone like Satoshi would maintain their privacy. It's available in clients like thunderbird with enigmail, and gpg4win all free and open-source mostly from Hal and Phil and the many other contributors. It has protected millions and millions of communications.

Bitcoin
Hal Finney began mining when the difficulty for Bitcoin was 1. He also received the first Bitcoin transaction ever recorded. Funny enough NewsWeek stated Satoshi was found when they released that Dorian Nakamoto was Satoshi. Turns out he and Hal Finney went to the same school and he lived only Blocks (pun intended) from Hal growing up.

Hal Finney was one of the most active responders to the Bitcoin announcement email, along with Ray Dillinger and James A. Donald.

Once Bitcointalk started Hal Finney provided valuable feedback to the code and advice to Satoshi.

From his intro post on Bitcointalk: "I was more positive. I had long been interested in cryptographic payment schemes. Plus I was lucky enough to meet and extensively correspond with both Wei Dai and Nick Szabo, generally acknowledged to have created ideas that would be realized with Bitcoin. I had made an attempt to create my own proof of work based currency, called RPOW. So I found Bitcoin facinating." He references Wei Dai, and Nick Szabo. Wei Dai created a proposal called bmoney, which was similar to Bitcoin, and Nick Szabo is considered one of the fathers of smart contracts, and a long time cryptographic researcher. Both are still doing valuable cryptographic research and work inside and outside of Bitcoin.

Satoshi showed great respect for Hal.

He also showed great respect for Adam Back and his contributions and ideas about Zerocoin theory. Which is now basically a project run by Zooko Willcox O'hearne called http://z.cash an anonymous digital currency.

Satoshi seemed ultimately scared by the potential legal issues with wikileaks and one of his last posts expressed this. I suspect this was why Satoshi exited. I think Satoshi was more worried about day to day hassles legally and by others than some grand romantic story. Sounds like the PGP suit waiting to happen.

End of Life
Hal Finney developed ALS (Amyotrophic lateral sclerosis) in his late 50s. He died in August 2014 in Arizona. He was deeply missed. Hal was a family man who loved his kids, and had just finished his first half marathon before finding out. He opted to be cryopreserved so maybe some day science will find a way to bring this hero back. In one of his last posts to Bitcointalk which I cannot find, he mentioned he was programming while in his wheel chair with an interface using his eyes. He worked until he couldn't all the way to the end, his dedication was endless. He mentioned he left some Bitcoins in a safety deposit box, only a few ;).

A Cypherpunk Legend and Hero
Hal dedicated his life to systems that provide ownership specifically with private key cryptography. He believed in personal ownership. He gave his work away for free and benefited millions. Instead of privatizing his work he let anyone use it. He never sought attention or press and is a true hero behind the scenes. It's difficult to even say everything what he worked on because he was quiet about his contributions and known to ghost write. I truly believe his contributions led to amazing platforms like Bitshares and now steemit and I wanted you to all know about this amazing man who changed millions of lives with code and theory. I don't know or care if he's Satoshi, there's some smoking guns, what I know is he's a genius for the people and people will benefit from his code and work decades past his death. Remember Hal when you use Steemit. He has shown many the path now we continue the journey to privacy and personal ownership.