Comment on Service lets you "certify" a document using the Bitcoin blockchainComments−yonilevy12yI believe you could implement it in such a way that the coins involved are spendable, relying on "Pay to script hash": https://en.bitcoin.it/wiki/BIP_0016
Comments
I believe you could implement it in such a way that the coins involved are spendable, relying on "Pay to script hash": https://en.bitcoin.it/wiki/BIP_0016