Passkeys vs 2FA: Understanding the security landscape

Two technologies dominate modern account security: passkeys and two-factor authentication (2FA). Both move beyond the limitations of a single username‑password pair, but they do so in slightly different ways. This article explores how each approach works, how they stack up in terms of security, and how they can be implemented smoothly, so users can decide which fits best for their personal or business needs. 

How do passkeys work?

Both passkeys and 2FA add an extra layer of protection that makes it far harder for attackers to gain access, but they do so by leveraging different security principles.

Passkeys are built on a mature, well‑researched cryptographic primitive: public‑key infrastructure (PKI) and public key cryptography, which aims to replace passwords. When a user creates a device-bound passkey, the user’s device runs a secure enclave or trusted execution environment (TEE) that holds the private key. 

Unlike passwords, this private key remains on the device and is protected by a biometric or PIN lock. Any online service that supports a passkey only knows the public key, which cannot be used to reconstruct the private key. This strengthens online security. The public-private key pair method offers higher security than any other current authentication method. Passkeys help prevent phishing attacks on websites and apps by using a different process than traditional passwords.

Once a passkey has been created, upon login, the following process takes place:

1. Server challenge: The server sends a random nonce (number used only once) to the device.

2. Signature generation: With biometric authentication, the user’s device signs the nonce using the ECDSA or EdDSA algorithm (common choices are the secp256r1 curve for ECDSA and the ed25519 curve for EdDSA).

3. Signature verification: The website or app verifies the signature with the stored public key pair. If the signature matches, the user is authenticated.

Because the private key never leaves the device and is never transmitted over the network, an attacker who compromises the server cannot impersonate the user because they cannot authenticate a user's passkey. 

Even if attackers manage to steal the stored public key for an account, they cannot forge the required signature. This is a much stronger guarantee than the secrecy of a password, which can be stolen, guessed, or cracked. Synced passkeys provide stronger protection against data breaches than traditional passwords and help secure sensitive information.

While passkeys replace the password for an account entirely, 2FA adds a second factor to the existing password. This is why 2FA is often the first step many people take toward stronger security. It is already supported on nearly every platform, and it can be deployed using a variety of second‑factor methods, which include:

• Authenticator apps: Bitwarden Authenticator, Google Authenticator, Microsoft Authenticator, Authy, etc., that generate time‑based one‑time passwords (TOTP).  

• SMS codes: Unique codes that arrive at the user’s phone number.  

• Email codes: Codes that are sent to the user’s registered email address.  

• Hardware tokens: YubiKey or Duo Security’s hardware dongles, which provide a physical challenge‑response mechanism.

Each method balances convenience and security differently. 

Text message codes are convenient but can be intercepted through SIM swaps or network eavesdropping, so they’re typically recommended only for low‑risk accounts. However, some services, like many banks, only offer SMS or email codes for user verification.

2FA offers more security than a simple password, can be configured to suit user comfort levels, and enjoys widespread adoption. As an add‑on, 2FA doesn’t eliminate passwords, but it requires attackers to obtain both a correct password and the second factor to gain account access.

Passkeys: A public-private key challenge-response system, which is mathematically designed to be unforgeable as long as the private key never leaves the device. Because the private key is never exposed, even a compromised server cannot impersonate the user, so a bad actor cannot access an account.

This makes passkeys the most secure authentication method available today, combining cryptographic proof of possession with biometric or PIN verification in a seamless experience. And thanks to the additional layer provided by the device's fingerprint sensor or facial scanner, passkeys add biometric authentication to the process, helping prevent phishing attacks and other security breaches.

2FA: Adding a second factor dramatically raises the bar for attackers, who would need to guess or brute-force the password and obtain the second factor to access an account. 

• The strongest 2FA methods, such as hardware tokens or TOTP, are almost as secure as passkeys for many scenarios where account sign-in is required. 

• TOTP codes can be generated through standalone apps like Bitwarden Authenticator, and some password managers also offer built-in 2FA support. 

• SMS‑based 2FA is less secure because it relies on the integrity of the cellular network. However, it still provides a meaningful layer of defense against credential stuffing and brute‑force attacks. 

When choosing between passkeys and 2FA, think of security as a tiered system where passkeys sit at the very high end, while 2FA sits just below that, but still above basic password protection.

Passkeys

The way passkeys work might feel like a bit of a mystery. That's understandable, because they are relatively new. Passkeys work thanks to biometric sensors and facial recognition APIs in modern smartphones, laptops, and tablets. These biometric features activate the passkey during authentication. When creating a passkey, the public key is automatically registered with the server during setup. After that, logging in is as simple as tapping a finger on a sensor or looking at the screen. For many users, the experience feels almost invisible — no typing lengthy passwords and no remembering 2FA codes.

2FA

This setup typically involves linking an authenticator app or configuring a hardware token, such as hardware keys that follow FIDO Alliance standards. Once configured, the process is straightforward: enter a username and password, then type the code that appears on the authenticator app or type the code that came via SMS. Because 2FA has been around for a long time, there is a wealth of tutorials, help articles, and support resources available, and nearly all sites and services now support this extra layer of protection.

Comparison

Both methods require a small amount of initial configuration, but the added security and user privacy are worth the setup time. Creating a passkey reduces friction by eliminating the need to type codes, thanks to the two cryptographic keys, while 2FA gives users a tangible sense of added protection. Strengthening authentication practices through either method delivers better security and helps prevent data from ending up on the dark web.

Passkeys

No additional hardware is needed if a biometric‑capable device like a phone is already in use. The only cost incurred is on the business side, with the development effort required to expose the public key to the server. For service providers, this is a one‑time integration cost per platform.

2FA

By choosing an authenticator app on a device, the cost is essentially zero. Hardware tokens incur a small one‑time purchase cost; YubiKey, for instance, costs around $50 for a basic model. For businesses, licensing or subscription fees may apply to enterprise‑grade 2FA solutions like Duo or Okta.

What is the difference between phishing-resistant and phishing-proof? The term "phishing resistance" is used by many organizations, including NIST, CISA, Microsoft, and the FIDO Alliance. Additionally, NIST SP 800-63-4 (2025) defines phishing resistance and requires it for AAL3.

Phishing-resistant systems generally include the following security measures:

• Multifactor authentication (MFA): Requires users to provide additional verification, such as a code sent to their phone or a biometric scan.

• Phishing-resistant authentication protocols: Require the use of protocols like WebAuthn or FIDO2 to provide a more secure way to authenticate users.

• Security awareness training: Users must be educated on how to identify and avoid phishing attempts.

• Advanced threat detection: AI-powered threat detection can be used to identify and block suspicious emails or messages.

CISA also repeatedly advises organizations to implement phishing-resistant multifactor authentication, such as FIDO security keys or smart cards. As of 2025, Microsoft has aligned its guidance with Zero Trust, calling for phishing-resistant MFA and passwordless rollouts. Finally, the FIDO Alliance positions passkeys/FIDO2/WebAuthn as phishing-resistant and a replacement for legacy MFA (password + SMS). 

While passkeys are recognized as phishing-resistant at AAL2, NIST SP 800-63-4 specifies that only device-bound passkeys with non-exportable private keys meet AAL3 requirements. Syncable (multi-device) passkeys, which allow synchronization across devices through cloud services, are not permitted at AAL3 because the private key must be exportable for syncing. Organizations requiring AAL3 assurance should deploy hardware security keys, smart cards, or device-bound passkeys rather than syncable passkeys.

A phishing-proof system, in theory, is completely resistant to phishing attacks, implying that it is so secure that it's impossible to use phishing techniques to trick users into divulging sensitive information. In reality, however, it's nearly impossible to create such a system because, even with the most advanced security measures, there is always the risk of human error. Such systems would require:

• Unbreakable authentication protocols: A phishing-proof system would require using protocols that are theoretically unbreakable, such as quantum-resistant cryptography.

• Perfect security awareness: All users would have to be completely immune to social engineering tactics.

• Intrusion-proof design: The system would need to be designed with security in mind, using techniques like secure coding practices and threat modeling.

Phishing-resistant systems are designed to be highly secure and can be easily and successfully implemented. Carefully investigate any service that claims to offer fully phishing-proof systems before proceeding.

Choosing the right method depends on several factors. The first factor is the simplicity of setup. 2FA is easier to set up initially, but passkeys offer a higher level of security. When making a selection, consider these tips:

• High‑value accounts (banking, corporate admin): Use a hardware token for 2FA or switch to passkeys, if supported.

• General consumer accounts (social media, email): 2FA with a TOTP authenticator app provides strong protection and is widely supported.

• Low‑risk accounts: SMS or email 2FA can be acceptable, but consider upgrading to a stronger method if the account holds any sensitive data.

When debating passkeys vs 2FA, the answer depends on priorities:

• If maximum security is paramount and a phone with fingerprint and/or facial recognition is available, passkeys are the superior choice.  

• If quick, incremental improvement over standard username/password authentication that works across many platforms is the goal, 2FA, particularly with hardware tokens or TOTP apps, is the next best step.

Either way, this moves away from the vulnerabilities of password-only authentication and takes meaningful steps toward stronger protection.

Passkeys represent a significant leap forward in secure, user‑friendly login, while 2FA remains a powerful and widely adopted safeguard that can be tailored to the user’s needs. When evaluating the choice between passkey vs 2FA, consider the trade‑offs in security, convenience, and the resources required for implementation. Whichever path is chosen, you're taking a meaningful step toward stronger digital security.

For those already using the Bitwarden password manager, or considering adoption, passkey and 2FA can be managed on Apple and Android devices, as well as across all major operating systems, consolidating security within a single tool.