I was playing on the testnet and I mined a block. In the wallet I can see the block reward, but it looks like it has multiple inputs

Height 10, transaction <f5b8d5b7e5d1a110fa9fdecdd3dee12e87ed4828dca168f55a08069ffa151148>, received 0.000018272975
Height 10, transaction <f5b8d5b7e5d1a110fa9fdecdd3dee12e87ed4828dca168f55a08069ffa151148>, received 0.002000000000
Height 10, transaction <f5b8d5b7e5d1a110fa9fdecdd3dee12e87ed4828dca168f55a08069ffa151148>, received 0.090000000000
Height 10, transaction <f5b8d5b7e5d1a110fa9fdecdd3dee12e87ed4828dca168f55a08069ffa151148>, received 0.500000000000
Height 10, transaction <f5b8d5b7e5d1a110fa9fdecdd3dee12e87ed4828dca168f55a08069ffa151148>, received 7.000000000000
Height 10, transaction <f5b8d5b7e5d1a110fa9fdecdd3dee12e87ed4828dca168f55a08069ffa151148>, received 10.000000000000

These coins supposed to be newly generated, so why does it look like this? Why isn't it only 1 input?

1 Answer 1


The coinbase transaction has a single placeholder input - one of special type, unlike the usual "from key" inputs you see on other transactions.

The log you supplied shows only outputs. A coinbase transaction may have more than one output, since before rct outputs were split by denomination in order to make ring signatures work better. If this had not been done, and since coinbase transactions give idiosyncratic amounts, most of those outputs would otherwise not be able to sign with other outputs, since they'd be the only one of that amount of the chain (or at least among a very small group).

On current Monero, this is no longer the case. RingCT allows any rct output to sign with any other, and coinbase outputs are internally handled as rct, with a hardcoded mask, allowing them to masquerade as rct outputs. Thus, current coinbase outputs can have idiosyncratic amounts while still being able to sign with other rct outputs.

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