Anchor

Anchoring stores a hash on the blockchain, allowing anyone to verify that data hasn't been tempered with.

JSON

{
  "type": 15,
  "version": 3,
  "id": "8M6dgn85eh3bsHrVhWng8FNaHBcHEJD4MPZ5ZzCciyon",
  "sender": "3Jq8mnhRquuXCiFUwTLZFVSzmQt3Fu6F7HQ",
  "senderKeyType": "ed25519",
  "senderPublicKey": "AJVNfYjTvDD2GWKPejHbKPLxdvwXjAnhJzo6KCv17nne",
  "fee": 35000000,
  "timestamp": 1610397549043,
  "anchors": [
    "5SbkwAekNbaG8P1mTDdAE88mpWtCdET9vTmV2v9vQsCK",
    ...
  ],
  "proofs": [
    "4aMwABCZwtXrGGKmBdHdR5VVFqG51v5dPoyfDVZ7jfgD3jqc851ME5QkToQdfSRTqQmvnB9YT4tCBPcMzi59fZye"
  ],
  "height": 1069662
}
  • id and height should be omitted when broadcasting. These fields are set by the node.

  • Binary strings are base58 encoded.

  • timestamp is in microseconds since epoch.

  • fee includes 8 digits, so LTO * 10^8

Batch transaction

Up to 100 hashes can be anchored in a single transaction. Bundling multiple anchors in 1 transaction can help reduce transaction fees.

The Anchor fee is made up of two amounts: a fixed one plus a per-anchor one. The fees are calculated as:

0.25 + 0.1 * N

where N is the number of anchor hashes in the transaction. The total is rounded up to the nearest 100_000.

Binary schema

The binary data structure of the unsigned transaction.

#Field NameTypeLength

1

Transaction type

Byte (constant, value=15)

1

2

Version

Byte (constant, value=3)

1

3

Network id

Byte

1

4

Timestamp

Long

8

5

Sender's key type

KeyType (Byte)

1

6

Sender's public key

PublicKey (Array[Byte])

32 | 33

7

Fee

Long

8

8

Number of anchors

Short

2

9

Anchor 1 length (N)

Byte

2

10

Anchor 1

Array[Byte]

N

...

  • Anchor length and Anchor are repeated for each anchor hash.

  • The maximum length of an anchor is 100 bytes.

  • Network id can be obtained by taking the 2nd byte from the sender address.

  • Each key type has a numeric id in addition to the reference from the JSON.

  • Integers (short, int, long) have a big endian byte order.

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