op return – Understanding how ordinals work with the Bitcoin blockchain. What is strictly saved on the blockchain?

Minimal handbook disassembly instance

Simply to offer a concrete instance, let’s think about the very first ordinal: https://ordinals.com/inscription/6fb976ab49dcec017f1e201e84395983204ae1a7c2abf7ced0a85d692e442799i0

The format is documented at: https://docs.ordinals.com/inscriptions.html with an instance:

OP_FALSE
OP_IF
  OP_PUSH "ord"
  OP_PUSH 1
  OP_PUSH "textual content/plain;charset=utf-8"
  OP_PUSH 0
  OP_PUSH "Hiya, world!"
OP_ENDIF

When you run an area node:

bitcoind

we are able to question the transaction and disassemble it with:

bitcoin-cli getrawtransaction 6fb976ab49dcec017f1e201e84395983204ae1a7c2abf7ced0a85d692e442799 true

Among the many remainder of the disassembly we see:

"txinwitness":
  "152b336f7b6fc69be82df72bb4653eed7e075da88c491c0ad76451fcf0514dd667702aabdeca72cea1427124fc511da6d9ffb43b7e32b908fcef169b19dfc1f6",
  "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",
  "c04a3ca2cf35f7902df1215f823d977df1174048b062e03a44f71c2ee736a60cc5"
],

Let’s additional disassemble the massive center txwitness script which CLI sadly doesn’t mechanically disassemble for us. As per The best way to disassemble a bitcoin script? it may be accomplished with:

bitcoin-cli decodescript "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"

which supplies:

4a3ca2cf35f7902df1215f823d977df1174048b062e03a44f71c2ee736a60cc5
OP_CHECKSIG
0
OP_IF
6582895
1
696d6167652f706e67
0
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
OP_ENDIF

Disassembly

With the assistance of https://stackoverflow.com/questions/7826526/transform-hexadecimal-information-to-binary-using-a-linux-command we are able to convert the hex dumps to binary with xxd -r -p:

1. 6582895
   

   is a decimal quantity, in hex:

   printf "%xn" 6582895
   

   it’s:

   64726f
   

   and:

   printf 64726f | xxd -r -p
   

   provides dro, which is the inverse of ord, for ordinals. All of that is only a disassembly artifact, we are able to see that the precise knowledge accommodates 6f7264 within the traditional ord order.

2. 1 is the content_type tag in line with https://docs.ordinals.com/inscriptions.html So this specifies the filetype of the information that follows.

   printf 696d6167652f706e67 | xxd -r -p
   

   provides:

   picture/png
   

   which is the filetype.

   It’s price noting that the filetype was necessary for an inscription to be thought of legitimate and get a sound quantity, however this restriction was later dropped resulting in the creation of corresponding adverse cursed ordinals corresponding to: https://ordinals.com/inscription/4b9a822a057743813efbefa0dd21d0a01342ee793ce2ce5bd499a5f262187553i0

3. 0 specifies that the precise content material is developing. We are able to decode it with:

   printf '
   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
   ' | xxd -r -p > tmp.png
   

   which supplies our picture:

   tmp.png

   

Payloads are typically not contiguous within the block knowledge resulting from PUSHDATA opcodes

One essential reality about ordinals is that not like with OP_RETURN, the payload will not be essentially encoded contiguously.

In our instance, we see that two separate constants have been pushed to the stack.

This isn’t very express within the disassembly, however each has an OP_PUSHDATA2 opcode instantly earlier than it, which is encoded as byte 0x4d can deal with solely as much as 520 bytes at a time:

Due to this fact, you possibly can’t simply straight carve out the payloads from the blockchain knowledge, block parsing is required.

In our instance, the uncooked knowledge contained:

4d 0802 [ 89504e47 ... 190a3674 ] 4d 1101 [ 09b16c4b ... ae426082 ]

so there would have been a trash knowledge of 4d1101 if we had tried to carve out values straight with out parsing.

There could be a number of ordinals per transaction

Any legitimate:

OP_FALSE
OP_IF
  OP_PUSH "ord"

in txinwitness signifies the beginning of a brand new ordinal, and you may have a number of of these per transaction.

This is the reason there may be that i0 on the finish of the URLs at ordinals.com corresponding to: https://ordinals.com/inscription/6fb976ab49dcec017f1e201e84395983204ae1a7c2abf7ced0a85d692e442799i0

The i0 means “inscription 0” and serves to disambiguate between a number of totally different ordinals in the identical transaction.

i0, i1, and so forth. are simply taken in blockchain serialization order.

Examined on Ubuntu 24.04.