How can a non-miner store data in the block?

Question

If I am not a miner and would like to put arbitrary data in the block chain, is there currently any method or protocol to get a miner to add it for me?

Answer 1

There is a service named btcmsg which allows you to do this. Here is the announcement in bitcointalk. The website is at btcmsg.staticloud.com.

They use a simple protocol to write and read the messages in the blockchain:

BTCmsg Protocol v1 (2011-09-18)

Each message is represented by multiple payment which is calculated by the following algorithm:

1. Two first chars for message type ('01' for md5, '02' for ascii).
2. Then the message in hex (python binascii.hexlify).
3. Split the long string to groups of 4 hex digits.
4. Each group of 4 hex (e.g. 2 ascii letters from the message) is represented by a payment in satoshi (maximum 0xffff=65535).
5. The service fee (composed of a fixed part and a variable part times the amount of small payments required, minus the transaction fee) can be seen within the first transaction.