Verification
۱۴۰۵/۱/۲۷
Verification in cryptocurrency means checking that something is valid and matches its expected properties. The term covers several distinct processes — transaction verification, block verification, identity verification (KYC), and smart contract verification — all sharing the common goal of answering "can I trust this?"
Transaction verification
When a transaction is broadcast to the network, every full node independently verifies:
- Signature — the transaction is signed by the private key matching the sender's address
- UTXO status (Bitcoin-style chains) — the coins being spent actually exist and haven't been used before
- Balance (account-based chains) — the sender has enough funds
- Protocol rules — input sum ≥ output sum, transaction format is valid, smart contract execution succeeds
Verification is performed locally by every node, without trust in any third party.
Block verification
When a miner broadcasts a new block, nodes verify:
- Proof-of-work — the block hash meets the current difficulty target
- Merkle root — all included transactions hash up to the root in the block header
- Transaction validity — every transaction inside the block passes its own verification
- Parent link — the block correctly references its predecessor
Verification vs confirmation
- Verification — "is this transaction valid?" — done once, by every node
- Confirmation — "how deep is this transaction buried in the chain?" — grows with every new block on top
A transaction is verified the moment it's broadcast and checked; it gains confirmations as blocks are added.
KYC (identity) verification
Regulated exchanges (Coinbase, Binance, Kraken) require Know Your Customer verification — identity documents, proof of address, and often a liveness selfie. This is a legal requirement for custodial services but does not apply to self-custody wallets or most DeFi protocols.
Smart contract verification
On Etherscan and similar explorers, developers can verify a deployed contract by submitting its source code and compiler settings. The explorer recompiles the code and checks it matches the on-chain bytecode. Verified contracts display readable source code, enabling independent auditing.
