Bitcoin glossary

B

Bitcoin

Peer-to-peer payment network and digital currency launched in 2009, with no central bank or intermediary. Capitalised, it refers to the network; in lower case, to the unit (bitcoin, BTC).

Bitcoin address

Public identifier, derived from a public key, that you share to receive bitcoins. It can be shared safely.

Bitcoin vault

Term used by La Citadelle for a properly configured hardware wallet with a protected recovery phrase.

Blockchain

Public, shared and time-stamped ledger in which every Bitcoin transaction is recorded, in successive linked blocks.

C

Centralised exchange

Company that lets you buy and sell bitcoins. If you leave your funds there, it holds the keys.

Confirmation

Inclusion of a transaction in a block. Each new block added afterwards counts as an additional confirmation.

Custodial

Situation where an exchange or service holds the keys on your behalf. Convenient, but you depend on its solvency and security.

H

Halving

Halving of the miners' reward roughly every four years (every 210,000 blocks). It slows down the creation of new bitcoins.

Hardware wallet

Small dedicated device (Ledger, Blockstream Jade, BitBox02…) that keeps private keys offline and requires each transaction to be signed physically. It is the focus of the REMPART package.

K

KYC

"Know Your Customer": identity verification required by regulated exchanges before buying or selling.

L

Lightning Network

Network built on top of Bitcoin for near-instant, low-cost payments, suited to small amounts.

M

Mining

Activity that secures the network: specialised computers produce the proof of work needed to create blocks, in exchange for a reward.

Multisig

Multi-signature wallet that requires several keys (for example 2 of 3) to authorise spending. It removes the single point of failure.

N

Node

Computer that runs the full Bitcoin software, stores the blockchain and checks every network rule itself.

P

Passphrase

Optional password added to the recovery phrase that creates a separate wallet. It strengthens security but must also be backed up.

Password manager

Encrypted vault that generates and remembers unique, strong passwords for each of your accounts.

Phishing

Scam attempt using a fake message or website to obtain a password or recovery phrase. A recovery phrase must never be shared.

PIN code

Code that locks a hardware wallet. After several wrong attempts, the device resets: only the recovery phrase can then restore access.

Private key

Cryptographic secret used to sign, and therefore authorise, movements of your bitcoins. Whoever holds the private key controls the funds.

Proof of work

Bitcoin's consensus mechanism: producing a block requires verifiable energy expenditure, which makes tampering with the ledger extremely costly.

PSAN

French status for digital asset service providers (prestataire de services sur actifs numériques), supervised by the AMF and being replaced by the European licence under the MiCA regulation.

Public key

Key derived from the private key, used to verify your signatures and generate addresses without revealing the secret.

R

Recovery phrase (seed)

Sequence of 12 or 24 words generated by your wallet. It restores all your bitcoins: keep it offline and never share it.

S

Satoshi (sat)

Smallest unit of bitcoin: 1 bitcoin = 100,000,000 satoshis. Named after Satoshi Nakamoto, Bitcoin's pseudonymous creator.

Self-custody

Holding the private keys to your bitcoins yourself, without entrusting them to an exchange or a third party. This is the principle La Citadelle stands for.

Software wallet

App installed on a computer or smartphone. Simple and free, ideal to get started; it is the focus of the BOUCLIER package.

T

Tor

Anonymity network that hides your IP address. A Bitcoin node can use it to protect your privacy.

Transaction

Transfer of bitcoins signed with the sender's private key, broadcast to the network and then recorded on the blockchain.

Transaction fees

Amount paid to miners to include a transaction in a block. It varies with network congestion.

Two-factor authentication (2FA)

Second verification factor (app, physical key) required in addition to the password to log in to an account.

V

VPN

Virtual private network that encrypts your connection and hides your IP address, useful on public networks. It is part of the COFFRE package.

W

Wallet

Tool that generates and stores your keys and lets you receive and send bitcoins.

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