How are the originated contract addreses (KT1) computed?

Question

How are smart contract addresses (those that start with KT1) computed?

I would like to know whether CHAIN_ID is somehow used in its computation, or it is possible to have two KT1 contracts with identical addresses on different chains.

Answer 1

In case someone needs precise calculations.

Say, you have an operation group hash onvsLP3JFZia2mzZKWaFuFkWg2L5p3BDUhzh5Kr6CiDDN3rtQ1D and an origination index 0 which is increased for every origination operation in the group including internal operations. In order to calculate originated contract hash you need to do:

1. Base58 decode (with checksum) the opg hash (34 bytes)
2. Remove 2-byte prefix (32 bytes)
3. Convert index (int32) to bytes (4 bytes)
4. Concatenate opg hash and index bytes (36 bytes)
5. Take Blake2b hash with digest size=20 (20 bytes)
6. Prepend 3-byte prefix \002\090\121
7. Base58 encode (with checksum)

In the result you get KT1UvfyLytrt71jh63YV4Yex5SmbNXpWHxtg

When you call run_code RPC endpoint a dummy contract is originated. Its address is calculated the same way, but a zero opg hash (\x00 32 times) is used. For every CREATE_CONTRACT instruction the origination index is increased.

The dummy originated contract address is thus always KT1Mjjcb6tmSsLm7Cb3DSQszePjfchPM4Uxm

Answer 2

KT1 addresses are computed from origination nonce. The origination nonce is made of operation hash (the operation that creates the origination) and its index (the index starts from 0 and it gets incremented for each origination in the operation).

The operation hash depends on block header of the branch where it was included.The CHAIN_ID depends on genesis block hash.

So on chains with different CHAIN_IDs the block hashes will differ, because they depend on their predecessors, and so you should never get the same KT1 addresses.

Answer 3

You have a good answer. If you want to learn more see these threads.

https://www.reddit.com/r/tezos/comments/91tis3/multiple_kt1_addresses

https://www.reddit.com/r/tezos/comments/9mxtkp/what_is_the_difference_between_manager_address/

Difference between tz1 and KT1 addresses

Difference between tz1 and KT1 addresses