Block chain

Integral to Bitcoin is a public ledger, a database with a sequential record of all transactions, known as the block chain, that records bitcoin ownership at present and at all points in the past. By keeping a record of all transactions, the block chain prevents double-spending, a problem particular to digital money. The block chain identifies receivers by Bitcoin addresses, not individuals’ names, but the flow of bitcoins can give clues as to who owns them. Bitcoin intermediaries, such as exchanges, are required by law in many jurisdictions to collect personal customer data.

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