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Taproot | Bitcoin Glossary | Mapping Bitcoin

Taproot

Protocolo

Also known as: BIP341

A major Bitcoin soft fork activated in November 2021 (BIPs 340-342) that introduces Schnorr signatures and Merkelized Alternative Script Trees (MAST). Taproot improves privacy by making complex transactions (multisig, timelocks) look identical to simple payments on-chain.

Overview

Taproot is the most significant Bitcoin protocol upgrade since SegWit, activated at block 709,632 in November 2021. Defined across BIPs 340, 341, and 342, Taproot bundles three interconnected improvements: Schnorr signatures, Merkelized Alternative Script Trees (MAST), and Tapscript. Together, these changes improve Bitcoin's privacy, efficiency, and smart contract capabilities.

Key Components

Schnorr Signatures (BIP340)

Schnorr signatures replace ECDSA for Taproot outputs, providing several advantages:

  • Linearity: Multiple signatures can be aggregated into a single signature, enabling efficient multisig schemes.
  • Smaller size: Schnorr signatures are 64 bytes versus ECDSA's ~72 bytes.
  • Provable security: Schnorr has a formal security proof under the random oracle model.

MAST (BIP341)

        Taproot Output
       /              \
  Key Path          Script Path
  (single sig)     (Merkle tree of scripts)
                       /        \
                    H(AB)      H(CD)
                   /    \      /    \
                 A: 2of3  B: timelock+sig
                 C: hash  D: emergency
                   preimage   recovery

The key path allows spending with a single aggregated signature, while the script path reveals only the specific branch being used. Unused branches remain hidden, preserving privacy and reducing on-chain data.

Privacy Improvement

The most impactful aspect of Taproot is that cooperative key-path spends for multisig, timelocked, and other complex spending conditions all produce identical-looking on-chain transactions — a single public key and a single signature. An observer cannot distinguish a 3-of-5 multisig spend from a simple single-key payment if the key path is used.

Pay-to-Taproot (P2TR)

Taproot introduced a new output type, P2TR, which uses SegWit version 1 addresses starting with bc1p. All Taproot outputs look identical regardless of their underlying complexity, further enhancing fungibility and privacy.

Common Misconceptions

  • Taproot does not break backward compatibility. As a soft fork, older nodes still accept Taproot blocks.
  • Taproot does not inherently enable all smart contract functionality — it provides building blocks that make future protocol development more practical and private.

Términos Relacionados

Schnorr SignatureCriptografía

A digital signature scheme activated on Bitcoin through the Taproot upgrade (BIP340). Schnorr signatures are mathematically simpler and more efficient than ECDSA, and their key property of linearity enables signature aggregation (MuSig), improving privacy and scalability.

TapscriptProtocolo

The updated script execution rules introduced by BIP342 as part of the Taproot upgrade. Tapscript modifies several opcodes and introduces new ones for use within Taproot script-path spends, enabling more flexible and efficient smart contracts on Bitcoin.

P2TRProtocolo

Pay-to-Taproot, the output type introduced by the Taproot upgrade (BIP341). P2TR addresses start with 'bc1p' and combine Schnorr signatures with MAST (Merkelized Alternative Script Trees) to enable more private and efficient complex spending conditions.

Soft ForkProtocolo

A backward-compatible change to Bitcoin's consensus rules that tightens existing rules (making some previously valid blocks/transactions invalid). Non-upgraded nodes still accept new blocks, though they may not fully validate the new rules. SegWit and Taproot were soft forks.