Notes on building a Cosmos wallet

Most of the core wallet primitives remain the same. Cosmos uses secp256k1 to generate public and private keypairs, so the process to derive keys is the same as any ETH wallet
Furthermore, I can build Cosmos wallets to fit the BIP39 standard to use mnemonic phrases to generate a seed, and then follow the BIP32 standard to create an HD Cosmos wallet
I can follow BIP44 as well to make a multicurrency wallet, with ATOM being just one particular branch in the tree path. Specifically, it is 118'.

Differences

The main difference will be in creating and sending transactions.
- Creation: Cosmos TXNs have a different format than ETH transactions. I must follow the Cosmos specification or else Cosmos nodes will not recognize the format of the transaction and mark it as invalid.
- Signing: This process will just involve signing the transaction with the private keys, which are the same keys used in ETH. However, the exact steps may differ, ie, signing the hash of the txn.
- Sending: Currently, I'm relying on Infura to send my signed ETH txn to and ETH node, which then broadcasts the TXN to the network. Obviously this won't work for Cosmos, so I'll have to figure out a way to broadcast the Cosmos txns created by this wallet

Creation: lookup the Cosmos specification for txns. Since Cosmos defines txns in Go/protobuf format, I'll need some way to interface with this. It seems that a rust crate implements the txn protobufs in Rust instead of Go, so I can just use this.
Sending: look into how Keplr, other Cosmos wallets send their transactions. Is there a 3rd party service analogous to Infura but for Cosmos? Alternatively, I can look into running my own node.

gRPC
REST
Tendermint RPC
The above I think I need access to a node/am running a Cosmos node
I can use REST/Tendermint RPC and just send json encoded transaction instead of protobufs?
Current plan: use datahub Cosmos REST API to send RawTxns