Can someone help me understand what these scripts mean?

Question

Could someone explain what the commands i have in bold do? if possible. Thank you.

Transaction URL www.blockchain.com/btc/tx

Input Scripts- ScriptSig: PUSHDATA(71)[3044022069f0c9da12ce7b002c68d25e4445191b149627987367fdec4e4b80e442379f3902202109994c46d8c6afd8e94542d07fa8a07da234f7537c4a1d639d2dcdd32f9c5b01] PUSHDATA(33)[03c26e5ff8c75d6272b2d9cd3a882c20315d440251deb79873b75b690d0b71f4cf]

Output Scripts- DUP HASH160 PUSHDATA(20)[264cf7a09b68a436bafc4d7281743d7f1c721ded] EQUALVERIFY CHECKSIG HASH160 PUSHDATA(20)[72cf56ba8b7312ae658debf033d88e4370b9a8f5] EQUAL

Answer 1

There is a nice introduction to script and already another answer explaining what these specific commands do, but I will try to explain what these scripts actually do.

They implement a very standard bitcoin transaction called pay-to-pubkey-hash transaction.

The idea is roughly the following. Let's call this transaction A. To spend the output of transaction A, another transaction will be created and broadcasted, let's call it B. In order to verify the validity of transaction B, one should:

1. combine the input script of B with the output script of A,
2. execute the combined script and verify that it returns True.

In this type of transactions, transaction B should provide an input script that puts two elements to the stack: the signature sig of the transaction and a corresponding public key pubKey. Note how the input script of transaction A is also doing exactly that.

Then the output script of transaction A will do the following (in your question you actually provide two output scripts merged together, because there are two outputs, I will focus on the first one):

1. Duplicate pubKey on the stack;
2. Hash one pubKey from the stack and verify that it is equal to 264cf7a09b68a436bafc4d7281743d7f1c721ded
3. Take sig and the remaining pubKey from the stack and verify the validity of the signature.

Answer 2

• PUSHDATA(71): Pushes the next 71 bytes onto the top of stack
• PUSHDATA(33): Pushes the next 33 bytes onto the top of stack
• DUP: Pushes a duplicate of the top stack item onto the top of the stack
• HASH160: Pop the top stack item off of the stack, hash it using SHA256 then that hash with RIPEMD160, and push the resulting hash to the top of the stack
• PUSHDATA(20): Push the next 20 bytes onto the top of the stack
• EQUALVERIFY: Check that the top two stack items are equal. If they are, do nothing. If they are not, immediately fail execution
• CHECKSIG:Pop the top stack item and interpret it as a public key. Pop the next stack item and interpret it as a signature. Check that the signature verifies to that public key when the message that is signed is a modified version of the transaction containing the signature. If the signature is valid, push OP_TRUE to the top of the stack. If it is false, push OP_FALSE to the top of the stack.

A full description of all script opcodes and their actual byte values can be found on the Bitcoin wiki.