FIDO authentication (Fast IDentity Online) is a set of open standards developed by the FIDO Alliance to provide strong, passwordless authentication for online services and applications. Rather than relying on traditional passwords, FIDO uses public key cryptography combined with methods, such as biometrics (fingerprint or facial recognition), security keys, or PIN codes to securely verify a user’s identity. In FIDO authentication, the private key used for authentication is stored exclusively on the user’s device and never transmitted, protecting sensitive credentials from phishing and server-side attacks.
FIDO authentication leverages a challenge-response mechanism based on asymmetric (public/private) key cryptography:
During registration, the user’s device generates a unique key pair: a public key (shared with the online service) and a private key (kept securely on the device).
When logging in, the service sends a cryptographic challenge. The user’s device signs this challenge with the private key, proving possession without revealing the key itself.
Biometric verification, a PIN, or the presence of a hardware token may be used to unlock the private key for this signing process.
The service verifies the signed response using the public key. No sensitive credential or biometric data ever leaves the user’s device.
This architecture makes FIDO authentication inherently secure and resistant to phishing, credential theft, and man-in-the-middle attacks. More information on FIDO and passkeys can be found at https://www.fidoalliance.org/how-fido-works/.
Key components of FIDO authentication
FIDO2:
FIDO2 is the latest evolution of FIDO standards, designed for passwordless authentication across the web. It consists of two main elements:
WebAuthn: A W3C standard that enables browsers and web applications to interact with authenticators using public key cryptography. More details here.
CTAP (Client-to-Authenticator Protocol): Allows communication between browsers, operating systems, and external authenticators, such as security keys.
FIDO2 supports both roaming authenticators (such as USB or NFC keys) and platform authenticators built into devices (like Windows Hello or Apple Face ID).
WebAuthn (Web Authentication API)
WebAuthn is a critical API for enabling secure authentication on web platforms using public key credentials. It allows sites to offer passwordless and multi-factor sign-in with external hardware or built-in device capabilities.
Key roles:
o Relying party: The website or service requesting authentication. o Client: The user’s browser or application. o Authenticator: The user’s device or security key.
WebAuthn improves both security and user experience and is central to FIDO2 adoption.
Passkeys
Passkeys are user-friendly, device-bound cryptographic credentials that enable passwordless logins. They simplify authentication by leveraging device biometrics or PIN in place of entering a password, storing the private key safely on the user’s device.
Biometric, security key, or PIN; no password memorization
Must remember/manage passwords
Credential management
Device-bound, automatically handled by authenticator
User must create, remember, and update
Regulatory compliance
Meets or exceeds modern authentication standards
May not fulfill regulatory security criteria
Fraud risk
Significantly reduced via strong authentication
High risk of theft, phishing, account takeover
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Use cases: Banking and payments FIDO authentication is increasingly adopted in:
Banking: Secure online banking logins, account access, and transaction approvals without SMS or one-time password (OTP) codes. For example, Entersekt’s implementation has helped some banks reduce phishing attacks by 99% and eliminate fraud losses by migrating away from OTPs. Learn more about Entersekt’s account takeover (ATO) fraud prevention solution.
Payments: Card issuers and payment providers use FIDO for transaction authorization, such as 3-D Secure, improving both security and customer convenience. Passkeys also reduce checkout friction and abandonment rates. See Entersekt’spasswordless authentication use casefor more details.
How FIDO supports phishing-resistant security FIDO authentication offers advanced protection against phishing and credential-based attacks through:
Origin-bound authentication: Public key credentials are cryptographically tied to the specific website or app, preventing their misuse on lookalike phishing sites.
Device-bound private keys: Even if a public key is exposed, access is impossible without the matching private key on the user’s device.
Biometric verification: Local biometric checks (such as fingerprint or facial recognition) add another layer, ensuring the real user is present.
No shared secrets: Server breaches yield no usable credentials because no password or private key is stored centrally.
This makes FIDO an essential standard for organizations seeking to deploy phishing-resistant multi-factor authentication (MFA) and achieve regulatory compliance.