@ -118,9 +118,9 @@ latexmath:[ S = F{sign}(m, k) ]
This signature S can be independently verified by anyone who has the public key K (corresponding to private key k), and the message:
latexmath:[ S' = F{verify}(m, K, S) ]
latexmath:[ F{verify}(m, K, S) ]
If S' matches S, then the verifier can confirm that the message m was signed by someone who had access to the private key k. Importantly, the digital signature proves the possession of the private key k at the time of signing, without revealing k.
If F_verify_ returns a true result, then the verifier can confirm that the message m was signed by someone who had access to the private key k. Importantly, the digital signature proves the possession of the private key k at the time of signing, without revealing k.
Digital signatures use a cryptographic hash algorithm. The signature is applied to a hash of the message, so that the message m is "summarized" to a fixed-length hash H(m) that serves as a fingerprint.
@ -201,23 +201,25 @@ or use the short link (case sensitive):
http://bit.ly/AliceTx
==== Output identifiers
==== Output identifiers (outpoints)
Similarly, since every transaction has a unique ID, we can also identify a transaction output uniquely by reference to the transaction ID and the output index number. The first output in a transaction is output index 0, the second output is output index 1 and so on. By convention we write an output identifier as the transaction ID, a colon and the output index number:
Similarly, since every transaction has a unique ID, we can also identify a transaction output uniquely by reference to the transaction ID and the output index number. The first output in a transaction is output index 0, the second output is output index 1 and so on. An output identifier is commonly known as an _outpoint_.
By convention we write an outpoint as the transaction ID, a colon and the output index number:
.Identifying an output by transaction ID and index number
Output identifiers are the mechanism that links transactions together in a chain. Every transaction input is a reference to a specific output of a previous transaction. That reference is an output identifier: a transaction ID and output index number. So a transaction "spends" a specific output (by index number) from a specific transaction (by transaction ID) to create new outputs that themselves can be spent by reference to the transaction ID and index number.
Output identifiers (outpoints) are the mechanism that links transactions together in a chain. Every transaction input is a reference to a specific output of a previous transaction. That reference is an outpoint: a transaction ID and output index number. So a transaction "spends" a specific output (by index number) from a specific transaction (by transaction ID) to create new outputs that themselves can be spent by reference to the outpoint.
Here's the chain of transactions from Alice to Bob to Chan to Dina, this time with output identifiers in each of the inputs:
Here's the chain of transactions from Alice to Bob to Chan to Dina, this time with outpoints in each of the inputs:
[[tx_chain_vout]]
.Transaction inputs are output identifiers forming a chain
image::images/tx6.png["Transaction inputs are output identifiers forming a chain"]
.Transaction inputs are outpoints forming a chain
image::images/tx6.png["Transaction inputs are outpoints forming a chain"]
The input in Bob's transaction references Alice's transaction (by transaction ID) and the 0 indexed output.
The input in Chan's transaction references Bob's transaction by ID and the 1st indexed output, because Bob's
The input in Chan's transaction references Bob's transaction by ID and the 1st indexed output, because the payment to Chan is output #1. In Bob's payment to Chan, Bob's change is output #0.footnote:[Recall that change doesn't have to be the last output in a transaction and is in fact indistinguishable from other outputs]
Andreas M. Antonopoulos
3 years ago