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Entry blockchain files from Bitcoin tidy contracts: Fragment 5

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This post was as soon as first printed on Medium.

Building upon the root laid out in earlier ingredients of the series, now we get demonstrated implement relative locktime in Bitcoin, with out fresh opcode OP_CheckSequenceVerify.


A timelock restricts the spending of some bitcoins till a specified future time or block height. There are two kinds of timelocks:

  1. Absolute: as an illustration, one can provably lock up 1,100,000 bitcoins till block height 800,000, or till January 1st, 2025.
  2. Relative: as an illustration, one can lock up 21 bitcoins that might completely be spent after 100 blocks or 3 days.

To allow absolute and relative timelocks, fresh opcodes OP_CheckLockTimeVerify/OP_CLTV and OP_CheckSequenceVerify/OP_CSV had been launched in BIP65 and BIP68/112/113, respectively.

Relative locktime with out OP_CSV

Restoring the genuine Bitcoin protocol, Bitcoin SV has reverted the aforementioned adjustments. It turns out OP_CSV might additionally fair additionally be utilized with the genuine protocol.

Relative Transaction Timelocks

In Fragment 1, now we get confirmed obtain admission to the block containing a given contract UTXO. Combining this block header with the desired relative timelock, we can know the earliest block that the UTXO might additionally fair additionally be spent. We request any block after the decrease-off date to be on the market for unlocking the UTXO, with out a doubt placing a relative timelock on it as OP_CSV does. The beefy code is listed below.

CheckSequenceVerify Contact

Line 11 shows unlocking according to unix time (e.g., in seconds). validateHelper() feature at Line 33 verifies every the block containing the UTXO and a most modern block are first fee (Line 41–42). It also verifies the dilapidated block in actual fact contains the UTXO (Line 34–38) utilizing the same contrivance as in Fragment 1. Line 15 ensures required time has elapsed since the UTXO is mined.

Line 19 shows unlocking according to block height (e.g., series of blocks). Line 24–25 obtain heights of the 2 blocks as in Fragment 3. Line 27 tests specified series of blocks were mined after the UTXO.


Apart from OP_CSV, now we get previously utilized OP_CLTV with none commerce to the fresh Bitcoin protocol. There are two implications:

  1. Every opcodes must no longer vital to enabled UTXO-level timelocks, as previously notion.
  2. All employ circumstances enabled by OP_CSV/CLTV, such as lightning networks, sidechains, and CLTV-fashion fee channels, might additionally fair additionally be without extend constructed on the genuine Bitcoin, if desired.

Build a query to: CoinGeek Recent York panel, Bitcoin & Blockchain – Can Accurate Price Come from Accurate Utility?

Recent to Bitcoin? Test out CoinGeek’s Bitcoin for Inexperienced persons section, the final handy resource files to be taught more about Bitcoin—as on the initiating envisioned by Satoshi Nakamoto—and blockchain.

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