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.

V3 (current)

#	Field Name	Type	Length
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.

V1

#	Field Name	Type	Length
1	Transaction type	Byte (constant, value=15)	1
2	Version	Byte (constant, value=1)	1
3	Sender's public key	PublicKey (Array[Byte])	32
4	Number of anchors	Short (constant, value=1)	2
5	Anchor 1 length (N)	Short	2
6	Anchor 1	Array[Byte]	N
...
7	Timestamp	Long	8
8	Fee	Long	8

• Anchor length and Anchor can be repeated for each anchor hash.

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