Transaction Signature
Pronunciation: tran-ZAK-shun SIG-nuh-cher
Definition
A transaction signature is cryptographic evidence that an authorized key approved specified transaction data under a blockchain's signing rules. It does not reveal the private key that produced it.
Overview
What it means and why it exists
A transaction signature is cryptographic evidence that an authorized key approved specified transaction data under a blockchain's signing rules. It does not reveal the private key that produced it.
How it works
A wallet constructs the message or digest required by its chain and signs with a private key. Nodes verify the signature against a public key and check the other spending conditions. On Bitcoin, the signed digest depends on transaction structure and sighash settings; Taproot key-path spends use Schnorr signatures, while legacy and many SegWit spends use ECDSA.
Technical details worth understanding
The signature binds chosen parts of the transaction; it is not necessarily a readable promise to a merchant. Sighash flags can change which inputs and outputs are committed. On account-based chains, the signature typically authorizes an account transaction including nonce and chain identifiers; smart-account authorization may use contracts instead.
What can go wrong
A mathematically valid signature does not ensure adequate balance, valid nonce, contract execution or inclusion in a block. Signing unfamiliar transaction data can approve a malicious transfer. A service should verify chain identity and transaction contents before relying on an external signature.
Practical checks
Before signing, inspect both recipient and permitted transaction changes; signature hashing rules can create subtle differences. When validating signatures, use the correct chain and algorithm rather than a generic 'signed' flag. For business flows, record the human approval separately because cryptographic authorization does not reveal which employee intended a payout.
Related concepts
Blockchain, Bitcoin (BTC), Transaction Hash.
Further reading
Example
A buyer signs a Bitcoin payment to a shop. The shop can verify the incoming transaction through the network; it never needs the buyer's seed phrase. The signature does not establish the sender's personal identity or ownership of every address visible in the transaction.
Comparison
A digital signature authorizes data; a private key creates signatures and a public key helps verify them. A transaction hash identifies encoded data, whereas a signature demonstrates authorization under a key.
Key Takeaway
The signature binds chosen parts of the transaction; it is not necessarily a readable promise to a merchant.
Sources
- FIPS 186-5: Digital Signature Standard — NIST (2026-08-02)
- Ethereum Transactions — Ethereum.org (2026-08-02)
- Bitcoin Developer Guide: Transactions — Bitcoin.org (2026-08-02)