What determines coin uniqueness?

[jhb]

What determines that a coin is unique?

hash of:

• serial
• serial + signature
• whole payload
• serial + mint_key_id
• ....

[nilstoedtmann]

See also

On 01/23/2013 01:45 PM, Joerg Baach wrote:

If I follow your thoughts then we need the serials to be so long to be practical collision free (if you user proper randomness).

Of course, as per Chaum. See https://github.com/OpenCoin/opencoin-memoranda/blob/master/opencoin-v3.txt#L326

    serial = base64(128bit random number) [[This random
                          value is generated by clients. A high entropy
                          (crypto grade quality) is important.]]

so maybe storing the serial is enough?

👍

The serial (or maybe serial+mind_key_id) should be the unique coin identifier. And i do not see any protocol-side reasons to store anything else in the DSDB [1].

There might be other reasons to store whole coins, e.g. to harden the DSDB against manipulation. But that is a issuer-side implementation/operations question and not relevant to the protocol.

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[1] For i minute i was thinking that there might be a very different reason to store whole coins at the DSDB: they could serve as issuer-signed reject reasons in case of double-spending attempts. But in most cases, the double-spend coin will be identical to the originally accepted one; also if we want to sign messages, the signatures needed to be time-stamped - so this would not really work ...

[jhb]

In the last conf call we decided that for now its the serial only.