It's a nice tribute to Len. Len's indirectly the reason I live in San Francisco today, and why I moved here without a job after graduating college. Through Len I met people who are my close friends in the hacker community today. The last time I heard from Len was four days before his death, and sadly, there was no indication that there was anything amiss.
I'm not sure of the exact circumstances of Len's passing, and I'll probably never really know. Instead, I'll just say that for all of you reading this today -- if you suffer from depression or feel a deep darkness over you, please seek help. Depression is a disease, and it can be treated. So while it may seem hopeless, or that nobody knows of the deep burden you carry, give it a chance. There was a time you felt good, even if it's hard to remember right now, and there's a way to get back to that place.
This is veering off the original topic, but isn't the ability to embed arbitrary text into the blockchain a bit problematic? Suppose a nefarious actor embedded text under current copyright (that s/he did not own) into the chain?
(or other data, though presumably text is the only medium where a possibly significant violation seems likely given the size limitations).
It's a lovely tribute to Len. It's perhaps worth pointing out that he was not a fan of Bitcoin. Here are some of his Bitcoin-related Tweets over the last few weeks of his life:
@glynmoody I wasn't happy with EFF's original acceptance of bitcoin, but I agree with you that their reasons for reversing course are "eh."
RT @mentalguy Also, if I had a significant BTC balance, I'd have kept it in PDF417 in a safe deposit box, not on someone's servers.
Retweeted by lensassaman
Those tweets read like someone who had a levelheaded view of Bitcoin, as compared to a minority of irrational Bitcoin fanboys. A Bitcoin bubble is a real issue. Volatility is a real issue. Anonymity is a real issue. Despite those issues, Bitcoin is still really cool.
Len Sassaman was a very prominent member of the cypherpunk community who recently passed away.
The blockchain is the record of all transactions that the bitcoin network has processed. The blockchain is how bitcoin clients know who sent how many bitcoins and to whom.
You are mixing two different terms here: The blockchain is a list of transactions that are linked to each other using cryptographic functions. Each block in the chain links to it's parent block. The genesis block is the first block created, it has no parent block. As proof that Bitcoin wasn't started before a specific date, the block references a The Times headline ("Chancellor on brink of second bailout for banks").
Dan Kaminsky figured out a way to embed ascii text into the block chain. I did not try to find out how he did it, but he probably created some transactions that include those strings. If you want to find out more about how he did it, he will give a talk at the Chaois Communications Camp related to Bitcoin.
(Presumably) Dan Kaminsky and Travis Goodspeed modified a bitcoin miner so that when it found a block, it would embed this tribute inside one of its unused field. (or rather, it embeds it in the transaction that is created as a part of generating a new block, the "coinbase".)
The bitcoin blockchain contains a record of every verified transaction that's happened to date - it needs this information to verify new transactions. Sometime in the last 500 blocks or so, Kaminsky and Goodspeed used a trick to embed this memorial inside a transaction, which is then dutifully stored by all bitcoin clients.
It is true that the network would have to evolve to a two-tiered structure with supernodes and client nodes. In Satoshi's paper it is explained how low-power client nodes can do "Simplified Payment Verification" (Section 8 of http://www.bitcoin.org/bitcoin.pdf). This is the mode implemented by bitcoinj (http://code.google.com/p/bitcoinj/) and it is already used to run bitcoin clients on android.
How else are you going to guarantee the irreversibility and proof in such a system? The block chain was very much a careful design consideration.
Every user doesn't even need the full set of transactions. I buy and sell bitcoins and have only run the desktop client for a few minutes to see what it looked like.
I'm not sure of the exact circumstances of Len's passing, and I'll probably never really know. Instead, I'll just say that for all of you reading this today -- if you suffer from depression or feel a deep darkness over you, please seek help. Depression is a disease, and it can be treated. So while it may seem hopeless, or that nobody knows of the deep burden you carry, give it a chance. There was a time you felt good, even if it's hard to remember right now, and there's a way to get back to that place.
RIP Len. ;-(