Want to create a digital timestamp without relying on an trusted third party to provider to sign your hashes?

http://en.wikipedia.org/wiki/Trusted_timestamping

Why not use the bitcoin block chain to store it for you in a way that doesn't involve trusting anyone.

The basic idea behind crypto timestamps is that you want to prove that you had a hash of some data at a certain time. Imagine you create a program and want to prove that you made it today so that years from now if someone claimed to have it first you can prove that you had it on this day. You would tar up your source, take a hash of it and have that hash signed by a trusted third party signing that they saw that hash from you today.

The trouble there is then you are relying on the reputation and security standards of some organization that might have a major security breech any time.

An answer is to use the bitcoin block chain. Imagine you have a SHA256 hash. Break it up into pieces and send each piece to some address. 5a85dc07abe09caf05b56603068d7255fa59737aacac7e959b7e7a544d322a9b becomes 5a85 dc07 abe0 9caf 05b5 6603 068d 7255 fa59 737a acac 7e95 9b7e 7a54 4d32 2a9b Each of these hex numbers becomes a small amount of BTC. You send these amounts of 16 addresses after sorting the addresses. That way, however it ends up in the transaction you can get it back into the proper order (by sorting the addresses again) and extracting your original hash.

This ends up as part of the block chain, inspectable and verifyable by anyone. All the blocks after the one your transaction gets set in prove that you had the hash when that block was made.

Of course there is a change return part of the transaction that can confuse things, so add a 17th send as a checksum. Then you can reassemble the hash even if the change is inside the expected range.

That is what this progam does. When do you "encode" it creates a sendmany command for the bitcoind RPC command line interface. It doesn't actually send anything, just creates the command. You can look it over and use it if you like.

The "decode" command pulls a specified transaction from blockexplorer and attempts to decode it into a hash, verifying the checksum.

To see some example transactions: http://blockexplorer.com/tx/f6f89da0b22ca49233197e072a39554147b55755be0c7cdf139ad33cc973ec46 http://blockexplorer.com/tx/49a130ce4255fc91061c3d1170cbc256f51ed671256df837500d59183cfdd64f

As is the style of bitcoin projects, I'll put a donation address: 1PqPyRvMHfjTuszjcRswL93fPWhGqj4q8g However, donate to blockexplorer first: 1Cvvr8AsCfbbVQ2xoWiFD1Gb2VRbGsEf28 Without that, this project would have taken a million multons rather than 4 hours.

Syntax

java -jar BitcoinTimestamp.jar encode HASH_STRING The hash string is expected to be a hexadecimal encoded output 256 bits in length Example: encode 5a85dc07abe09caf05b56603068d7255fa59737aacac7e959b7e7a544d322a9b Note: if you create a file 'hashcapture.list' it will be used for the destination addresses. if you don't do that, this program will use addresses of the author and your pitance will go to him. It should be on average 0.006 BTC + transaction fees. Your file must contain at least 17 addresses, whitespace delimited.

java -jar BitcoinTimestamp.jar decode TRANSACTION_ID Example: decode f6f89da0b22ca49233197e072a39554147b55755be0c7cdf139ad33cc973ec46