ZeroCT - Full implementation with Transaction Amount obfuscation support and ZeroCT Staking

[skreener]

• Adds support for Zerocoin Mint and Spend operations
• New type of address to anonymously receive coins
• Deterministic private address generated from master private key of the wallet
• Use of GMP for Bignum operations
• Use of threading for Mint and Spend verification
• Witnesser thread for pre-computing of coin witnesses
• Monitoring of public and private coin supply
• Staking with private coins
• Calculation of staking weight based on private coins
• Fees collected from public transactions are accumulated and only earned by public coin stakes
• Stakes using coins from the private pool earn in exclusive accumulated fees from private transactions
• New default data folder: NavCoin5 / navcoin5
• Testnet uses testnet4 to store chain data.
• Old NavTech functionality and references are removed
• GUI-level integrations of private transactions functionality
• Encryption of the obfuscation parameters for encrypted wallets
• New rpc commands:
  • getprivateaddress
  • privatesendtoaddress
  • dumpprivateparameters
• New daemon arguments:
  • -enablewitnesser: enables witnesser thread to precompute coin witnesses (default true)
  • -witnesser_block_snapshot: count of blocks to snapshot and backup witnesses value
  • -witnesser_blocks_per_round: count of checked blocks per witnessing round
• Includes libzerocoin test units

Consensus rules

• Transactions do not admit combinations of public and private coins as inputs
• Serial numbers and Mint coin values can only be spent once
• Spend/mint fee: per transaction weight

To do

• Include obfuscation parameters in dumpwallet output
• When a transaction size is too big, split it in different transactions containing the different spend proofs
• Accommodate wallet-related RPC commands to the new private transactions functionality
• Redesign/improve UX in the GUI
• Remove critical log entries which could compromise user's privacy
• Improve proof's verification time/general performance
• Testing ;-)

[mxaddict]

@aguycalled should we close this PR since this work was cancelled?