​
MsgStoreCode

Uploading the Wasm light client contract to the Wasm VM storage is achieved by means of MsgStoreCode: 
type MsgStoreCode struct {
  / signer address
  Signer string
  / wasm byte code of light client contract. It can be raw or gzip compressed
  WasmByteCode []byte
}
This message is expected to fail if:
  • Signer is an invalid Bech32 address, or it does not match the designated authority address.
  • WasmByteCode is empty or it exceeds the maximum size, currently set to 3MB.
Only light client contracts stored using MsgStoreCode are allowed to be instantiated. An attempt to create a light client from contracts uploaded via other means (e.g. through x/wasm if the module shares the same Wasm VM instance with 08-wasm) will fail. Due to the idempotent nature of the Wasm VM’s StoreCode function, it is possible to store the same byte code multiple times. When execution of MsgStoreCode succeeds, the checksum of the contract (i.e. the sha256 hash of the contract’s byte code) is stored in an allow list. When a relayer submits MsgCreateClient with 08-wasm’s ClientState, the client state includes the checksum of the Wasm byte code that should be called. Then 02-client calls 08-wasm’s implementation of Initialize function (which is an interface function part of ClientState), and it will check that the checksum in the client state matches one of the checksums in the allow list. If a match is found, the light client is initialized; otherwise, the transaction is aborted.

​
MsgMigrateContract

Migrating a contract to a new Wasm byte code is achieved by means of MsgMigrateContract: 
type MsgMigrateContract struct {
  / signer address
  Signer string
  / the client id of the contract
  ClientId string
  / the SHA-256 hash of the new wasm byte code for the contract
  Checksum []byte
  / the json-encoded migrate msg to be passed to the contract on migration
  Msg []byte
}
This message is expected to fail if:
  • Signer is an invalid Bech32 address, or it does not match the designated authority address.
  • ClientId is not a valid identifier prefixed by 08-wasm.
  • Checksum is not exactly 32 bytes long or it is not found in the list of allowed checksums (a new checksum is added to the list when executing MsgStoreCode), or it matches the current checksum of the contract.
When a Wasm light client contract is migrated to a new Wasm byte code the checksum for the contract will be updated with the new checksum.

​
MsgRemoveChecksum

Removing a checksum from the list of allowed checksums is achieved by means of MsgRemoveChecksum: 
type MsgRemoveChecksum struct {
  / signer address
  Signer string
  / Wasm byte code checksum to be removed from the store
  Checksum []byte
}
This message is expected to fail if:
  • Signer is an invalid Bech32 address, or it does not match the designated authority address.
  • Checksum is not exactly 32 bytes long or it is not found in the list of allowed checksums (a new checksum is added to the list when executing MsgStoreCode).
When a checksum is removed from the list of allowed checksums, then the corresponding Wasm byte code will not be available for instantiation in 08-wasm’s implementation of Initialize function.