Sign Bitcoin transactions

[olemis]

Feature description

Sign Bitcoin transactions. If complex , at the beginning use P2PKH only.

Is your feature request related to a problem? Please describe.
Implement messages for a finite state machine to sign Bitcoin transactions.

Describe the solution you'd like
A clear and concise description of what you want to happen.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context

Message for distributing BIP44 address should be already implemented. Just needs correct cointype value specified in message's Bip44AddrIndex struct.
Similar state machine for Skycoin , and for Bitcoin exist. Feel free to consider them as a reference.

Possible implementation

• Move Skycoin-specific messages onto a new messages-skycoin.proto file in protob repository.
• Add Bitcoin-specific messages definition in messages-bitcoin.proto
• Move Skycoin-specific handlers from fsm.c onto fsm_sky.c (same for headers if needed)
• Move implementations of functions selected above from fsm_impl.c onto fsm_sky_impl.c (same for headers if needed)
• Add new fsm_btc.c for Bitcoin messages handlers
• Add new fsm_btc_impl.c for Bitcoin message implementations
• Define Bitcoin signing state machine
• Create issue in fibercrypto/docs for documenting Bitcoin signing state machine
• Implement Bitcoin signing messages .
• Support for P2PKH
• Support for P2SH (if too complex or lengthy create new issue and add reference)
• Support for P2MS (if too complex or lengthy create new issue and add reference)
• Research other payment modes and add issues if anything relevant identified.
• Research specific address generation (Segwit?) and create new issues for implementing them

[olemis]

@stdevAdrianPaez what items are finished . Can you check them out ?