Legend

• VBK - VeriBlock
• BTC - Bitcoin
• Finalized - blocks that have 100% chance of being final, e.g. which will never reorganize. For BTC it is same to assume that all blocks behind 11 blocks from current tip are final. For VBK, 2000.

Description

Rebootstrapping is a process of changing bootstrap blocks stored in altchain.

Note

Example from vBTC: https://github.com/VeriBlock/vbk-ri-btc/blob/master/src/vbk/bootstraps.cpp

To properly validate every ATV and VTB, Altchain should maintain a SPV view on BTC and VBK blockchains. Every blockchain starts with a genesis block - a single hand-crafted block, which is a "root" of a tree.

Similarly, VBK and BTC blockchains should start with a root block. Since we don't start at block 0, we should specify at least 1 difficulty adjustment interval worth of contiguous blocks, otherwise we won't be able to statefully validate their difficulty. For BTC we require at least 2016 blocks, and for VBK we require at least 100 blocks.

Protocol

Warning

For Altchain mainnet you ALWAYS should use VBK mainnet and BTC mainnet, otherwise there will be serious security issues.

For Altchain Testnet, use VBK testnet and BTC testnet.

For automated testing/regtest, use VBK regtest_progpow and BTC regtest.

1. Fetch 2016 finalized contiguous BTC headers, and save height of first header.
   • Find btcStartHeight: if last BTC block height is 1M, then use heights 1M - F - 2016 where F is number of confirmations to consider block final, and 2016 is the number of blocks in single BTC difficulty adjustment interval. In our example btcStartHeight=1M-11-2016=997973
   • Find hash of block on btcStartHeight, for example 000000000d9fcff7c03867d8d6331506cb9ed885be4b098d9df1ec6c552b54f9
   • Use getblockheader <hash> RPC to get actual block header content. Serialized block header is always 80 bytes.
2. Fetch 100 finalized contiguous VBK headers, and save height of first header.
3. Hardcode btcStartHeight, btcHeaders, vbkStartHeight, vbkHeaders in bootstraps.cpp: https://github.com/VeriBlock/vbk-ri-btc/blob/master/src/vbk/bootstraps.cpp

Warning

ALL peers MUST have identical bootstrap blocks, otherwise they will fork, therefore we hardcode them in Altchain daemon. Similarly to having different genesis blocks of the same coin.