hash160: a 20-byte ripemd160 hash
salt: a random value appended to data in order to prevent reverse-lookups of the hashed data
name hash: a hash160 of a given name and a random salt -name encoding: a given name converted from base 40 to base 256
historical record hash: a hash of a data string generated from a representation of the namespace
update hash: a hash of the data to be associated with a given name

Data Encoding

Constraints:

40 bytes available in OP_RETURN
1 byte = 256 values
charspace of alphanumerics and a few special chars (-._+) = 40 values
1.5 name characters can fit in each byte

Field lengths

magic bytes = 2 bytes
name hash = 20 bytes
nameLen = 1 byte
name = 1 byte - 16 bytes
salt = 16 bytes
update hash = 20 bytes
historical record hash (truncated) = 16 bytes

Name encoding lengths

16 bytes = 24 characters
17 bytes = 25.5 characters
18 bytes = 27.0 characters
19 bytes = 28.5 characters
20 bytes = 30 characters
24 bytes = 36 characters

Transaction Senders/Name Owners

Each transaction operation has a "sender". If any pre-orders or name registrations occur as a result of a given transaction, the "sender" is also considered the "owner" of those pre-orders and/or name registrations.

In a transaction, the sender is established as the funder of the first non-OP_RETURN input.

Name Preorder (reserve)

magic bytes (2 bytes)
operation code (1 byte)
name/salt hash (20 bytes)

Name Claim (reveal)

magic bytes (2 bytes)
operation code (1 byte)
nameLen (1 byte)
name (up to 16 bytes)
salt (16 bytes)

Name Update

magic bytes (2 bytes)
operation code (1 byte)
nameLen (1 byte)
name (up to 16 bytes)
update hash (20 bytes)

Name Transfer

magic byte (2 byte)
operation code (1 byte)
nameLen (1 byte)
name (up to 16 bytes)

In a name transfer, name ownership is transferred to the recipient of the first non-OP_RETURN output, while name admin rights are given to the recipient of the second non-OP_RETURN output.

Misc.

Example of a transaction with an OP_RETURN and multiple outputs: https://blockchain.info/tx/1ae39745fd3891c16806bba44e6540944d145452ff156cab03076d7c08462e38?show_adv=true

Historical Record Hashes

Historical record hashes (16 bytes) are to potentially be added to name preorders and/or name transfers.

The historical record hash must be a hash of a data string generated from a snapshot of the namespace at some point in the recent past (e.g. the last 12 blocks).