Cryptography and cryptocurrencies
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    Slide http://ui-tutorweb.clifford.shuttlethread.com/comp/crypto251.0/lec02000/sl02010
Cryptography use by cryptocurrencies
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Cryptocurrencies use cryptography for several tasks, including:

* signing transactions using a private key
* verifying ownership of an amount to be spent using a public key
* summarising a transaction into a hash
* summaring all transactions in a block into a hash
* summarising a block into a hash
* defining criteria for a block hash to satisfy for a block to be acceptable