Monero vs Bitcoin Taproot: Percorsi Diversi per la Privacy

Understanding the Privacy Landscape

Bitcoin's Taproot upgrade, activated in November 2021, represented the most significant protocol change to Bitcoin since Segregated Witness (SegWit). Among its many improvements, Taproot was frequently described in the cryptocurrency media as a "privacy upgrade" for Bitcoin. This characterization, while not entirely incorrect, can be misleading if taken at face value. Taproot improves a specific, narrow aspect of Bitcoin privacy (script privacy) while leaving the fundamental transparency of Bitcoin transactions entirely unchanged. This article provides a rigorous technical comparison of what Taproot actually achieves versus the comprehensive privacy model that Monero implements by default.

What Bitcoin Taproot Actually Provides

Taproot is a bundle of three interconnected Bitcoin Improvement Proposals: BIP 340 (Schnorr signatures), BIP 341 (Taproot), and BIP 342 (Tapscript). Together, they change how Bitcoin transactions are constructed and verified, with meaningful implications for efficiency, flexibility, and a limited form of privacy.

BIP 340: Schnorr Signatures

Before Taproot, Bitcoin used ECDSA (Elliptic Curve Digital Signature Algorithm) for transaction signing. Taproot introduces Schnorr signatures as an alternative. Schnorr signatures offer several advantages:

Linearity: Schnorr signatures are mathematically linear, which means multiple signatures can be aggregated into a single signature through a process called key aggregation. If three parties need to sign a transaction (a 3-of-3 multisig), their three individual Schnorr signatures can be combined into a single signature that is indistinguishable from a regular single-signer signature. This is a genuine privacy improvement: an observer cannot tell whether a Taproot output was spent by a single key or by a multisig arrangement.

Batch verification: Multiple Schnorr signatures can be verified together more efficiently than verifying each independently. This improves node performance but has no direct privacy implications.

Provable security: Schnorr signatures have a formal security proof under the random oracle model, unlike ECDSA, which relies on ad-hoc security arguments.

BIP 341: Taproot (MAST Trees)

The core Taproot construction combines a Schnorr public key with a Merkelized Alternative Script Tree (MAST). This creates a spending condition that looks like a simple single-key spend in the common case but can fall back to complex script conditions if needed.

Here is how it works: A Taproot output commits to a public key Q that is computed as Q = P + H(P || m) * G, where P is the "internal key" (the key used for the cooperative spend path), m is the Merkle root of a tree of alternative spending scripts, G is the generator point, and H is a hash function. When spending via the cooperative path (the "key path"), the spender provides a Schnorr signature for the key Q. The transaction looks exactly like any other single-signature Taproot spend. When spending via an alternative script (the "script path"), the spender reveals only the specific script branch being used and provides a Merkle proof that the script is committed to in the MAST tree. Other unused script branches remain hidden.

What This Means for Privacy

Taproot's privacy improvement can be summarized as "script privacy": the ability to hide the spending conditions of a transaction. In practical terms, this means that a 2-of-3 multisig wallet, a lightning channel opening, a time-locked contract, and a simple single-key wallet all produce transactions that look identical on the blockchain when spent cooperatively. An observer cannot distinguish between these different transaction types.

However, Taproot does not provide:

• Sender privacy: The Bitcoin address spending the funds is fully visible.
• Recipient privacy: The Bitcoin address receiving the funds is fully visible.
• Amount privacy: The exact amount of every Bitcoin transaction is fully visible.
• Transaction graph privacy: The flow of funds from one address to another is fully visible and trivially traceable.

How Monero Achieves Comprehensive Privacy

To understand why Taproot does not make Bitcoin comparable to Monero in privacy terms, it is essential to understand the multiple layers of privacy that Monero implements simultaneously.

Ring Signatures: Sender Privacy

Every Monero transaction includes a ring signature that mixes the real spending output with 15 decoy outputs from the blockchain. An observer sees 16 possible senders for each transaction input and cannot determine which one is real. This is fundamentally different from Taproot, where the spending address is always explicitly and unambiguously identified.

Stealth Addresses: Recipient Privacy

When you send Monero to someone, your wallet generates a unique one-time stealth address for the transaction using the recipient's public address and random data. This one-time address appears on the blockchain as the destination of the funds, but it cannot be linked to the recipient's public address by anyone other than the recipient (who can detect it using their private view key). On Bitcoin with Taproot, the recipient's address is directly visible in the transaction output.

RingCT (Bulletproofs+): Amount Privacy

Monero uses RingCT (Ring Confidential Transactions) with Bulletproofs+ range proofs to cryptographically hide transaction amounts. The blockchain records a commitment to the amount (a Pedersen commitment) that allows nodes to verify that inputs equal outputs (no inflation) without revealing the actual values. With Bitcoin Taproot, every satoshi is counted and publicly visible.

Mandatory Privacy: The Network Effect

Perhaps the most critical difference is that Monero's privacy features are mandatory for all transactions. Every Monero transaction uses ring signatures, stealth addresses, and hidden amounts. This creates a large, uniform anonymity set where every transaction looks identical in structure. On Bitcoin, even with Taproot, the vast majority of privacy-enhancing features are optional. Users can choose to use CoinJoin, PayJoin, or Lightning Network for improved privacy, but most transactions remain completely transparent. This means the anonymity set for privacy-conscious Bitcoin users is limited to other users who actively choose the same privacy techniques.

Schnorr Signatures: Shared Foundation, Different Applications

Interestingly, both Monero and Bitcoin now use Schnorr-based signature schemes, but they apply them to fundamentally different problems.

Schnorr in Bitcoin (Taproot)

Bitcoin uses Schnorr signatures primarily for key aggregation and script privacy. The signature proves that the spender controls the private key corresponding to the Taproot output's public key. The main privacy benefit is that multisig and complex spending conditions look the same as simple single-key spends.

Schnorr in Monero (CLSAG)

Monero uses a Schnorr-based construction called CLSAG (Concise Linkable Spontaneous Anonymous Group signatures) for its ring signatures. CLSAG proves that the signer controls one of the private keys in a set of public keys (the ring), without revealing which one. The "linkable" property ensures that the same output cannot be spent twice (preventing double-spending) by producing a deterministic key image that is unique to each output but does not reveal which output it corresponds to.

The mathematical foundation is similar (both rely on the discrete logarithm problem on elliptic curves), but the cryptographic construction and privacy goals are entirely different. Taproot Schnorr proves "I own this specific key." CLSAG Schnorr proves "I own one of these 16 keys, but I will not tell you which one."

MAST Trees vs Ring Signatures: A Structural Comparison

MAST (Merkelized Alternative Script Trees) and ring signatures both provide a form of "hiding among alternatives," but they hide fundamentally different things:

MAST hides unused spending conditions: If a Taproot output has three possible spending paths (Alice's key, a 2-of-3 multisig, or a time-locked recovery key), and Alice spends it with her key, the multisig and time-lock paths remain hidden. But Alice's identity as the spender is fully revealed.

Ring signatures hide the actual spender: A Monero ring signature includes the real spender's output among 15 decoy outputs. The transaction is valid for any of the 16 outputs in the ring, and no observer can determine which one was actually spent.

These are complementary concepts, not competing ones. In theory, a system could use both MAST trees (to hide spending condition complexity) and ring signatures (to hide the actual spender). Monero's upcoming FCMP++ will achieve something even stronger: proving membership in the entire UTXO set without revealing which output is being spent, making the ring signature concept obsolete in favor of a strictly superior full-chain membership proof.

What Taproot Does Well (And Why It Matters)

Despite the limitations outlined above, Taproot is a meaningful improvement for Bitcoin that should not be dismissed:

• Lightning Network privacy: Taproot significantly improves Lightning Network privacy by making channel opens and cooperative closes look like regular single-key transactions. Before Taproot, Lightning channels were easily identifiable on-chain by their distinctive 2-of-2 multisig structure.
• Smart contract privacy: Complex Bitcoin contracts (escrow arrangements, time-locked savings, inheritance schemes) no longer reveal their complexity on-chain when spent cooperatively. This is a genuine and valuable privacy improvement.
• Efficiency: Taproot transactions are smaller and cheaper to verify than equivalent pre-Taproot transactions, particularly for multisig and complex spending conditions. This efficiency improvement benefits the entire Bitcoin network.
• Foundation for future privacy improvements: Taproot's Schnorr signature scheme enables future privacy improvements like cross-input signature aggregation, which could reduce the on-chain footprint of CoinJoin transactions and make them cheaper and more practical.

The Privacy Spectrum: From Bitcoin to Monero

Rather than viewing Bitcoin and Monero as binary "private or not private," it is more accurate to understand them as occupying different positions on a privacy spectrum:

Base Bitcoin (pre-Taproot): All transaction details are fully transparent. Sender, recipient, amount, and transaction graph are all publicly visible. Script types (multisig, time-lock, etc.) are identifiable.

Bitcoin with Taproot: Script type privacy is added. Cooperative multisig and complex contracts look like simple single-key spends. But sender, recipient, amount, and transaction graph remain fully transparent.

Bitcoin with Taproot + Privacy Techniques: Users who actively employ CoinJoin, PayJoin, Lightning Network, and careful UTXO management can achieve a moderate level of practical privacy. This requires significant effort, technical knowledge, and is limited by the small anonymity set of other users doing the same.

Monero (current): Sender is hidden among 16 ring members, recipient is hidden by stealth addresses, amount is hidden by RingCT. All privacy is mandatory and automatic. The anonymity set is all Monero transactions.

Monero (post-FCMP++): Sender is hidden among all outputs ever created. All other privacy properties remain. This represents the strongest transaction privacy achievable on any production cryptocurrency.

Conclusion

Bitcoin's Taproot upgrade is a well-engineered improvement that provides meaningful benefits for smart contract privacy and network efficiency. However, it does not address the fundamental transparency of Bitcoin's transaction model: senders, recipients, and amounts remain fully visible on every transaction. Monero's approach of mandatory, comprehensive privacy through ring signatures, stealth addresses, and confidential transactions creates a qualitatively different privacy guarantee that Taproot does not and was not designed to match. For users who require genuine financial privacy, Monero remains the purpose-built solution. Converting between Bitcoin and Monero is simple and private through MoneroSwapper, which enables KYC-free swaps that protect your financial privacy at every step.