2FA - Two-Factor Authentication
Signing in with two different kinds of proof, typically a password plus a one-time code or a security key.
AAGUID
A 16-byte identifier for an authenticator's make and model, used to allow specific hardware in enterprise policies.
Attestation
A signed statement from an authenticator about its own make and model, presented when a credential is created.
Backup
A second copy of your secrets on another device, so losing one does not mean losing everything.
BIP39
The standard that turns random entropy into a readable list of 12 or 24 words, with a checksum to catch typos.
Credential Stuffing
Trying a leaked email-and-password pair automatically across many other services at once.
CTAP2
The protocol a browser uses to talk to a security key over NFC, USB or Bluetooth.
Descriptor
A text string describing how a crypto wallet derives its addresses, so a watch-only wallet can be rebuilt without the private keys.
Discoverable Credential
A passkey stored in full on the authenticator, allowing sign-in without typing a username. Also called a resident key.
Encryption
Scrambling data so that only someone holding the right key can read it - the mechanism behind vaults, backups and passkeys alike.
Entropy
A measure of genuine randomness - and therefore the real measure of how hard a password or seed phrase is to guess.
FIDO2
The open standard behind every passkey, combining WebAuthn on the browser side and CTAP2 on the device side.
Hashing
A one-way transformation applied to a password before storage, so the service never keeps the password itself.
HOTP
A one-time password derived from a counter, valid until it is used.
Multi-Factor Authentication (MFA)
Proving your identity with evidence from two or more different categories.
NFC
Near Field Communication - the short-range radio link that lets a card or ring talk to a phone.
OTP
A one-time password - a short code valid for a single use or a brief window.
Passkey
A login credential made of two cryptographic keys, replacing your password - the private key never leaves your device.
Passphrase
An optional extra secret added to a BIP39 seed phrase, producing an entirely different wallet rather than locking the existing one.
Password
A secret string of characters used to prove your identity when signing in to an account.
Phishing
Tricking someone into handing over credentials through a message or a page that looks legitimate.
Recovery
Regaining access to an account or a device after losing the usual way in.
Relying Party
The website or service that asks for authentication and verifies the result.
Secure Element
A dedicated chip built to hold secrets and resist physical attack, with no way to export what it stores.
Security Key
A physical device used to authenticate, holding credentials in hardware rather than in software.
Seed Phrase
A list of 12 or 24 ordinary words that encodes every private key in a crypto wallet - the wallet itself, in readable form.
SIM Swapping
Persuading a mobile carrier to move your phone number to an attacker's SIM, so every SMS code arrives with them instead of you.
TOTP
A one-time password computed from a shared secret and the current time, changing every thirty seconds.
U2F
The first generation of the FIDO standard, a second factor rather than a password replacement.
Vault
The encrypted store holding your credentials, whether in software or on a device.
WebAuthn
The browser API that lets a website request a cryptographic signature instead of a password.