Passwordless Authentication and Passkeys 
A SaaS Migration Guide 

The password has been the weakest link in application security for as long as applications have had users, and the industry has finally committed to replacing it. Passwords get phished, reused across sites, stuffed from breach dumps, and guessed; every mitigation we've bolted on — complexity rules, forced rotation, SMS codes — has added friction without fixing the root problem, which is that a password is a shared secret a human has to remember and can be tricked into giving away. Passkeys change the model entirely. Built on the WebAuthn and FIDO2 standards and now supported across every major browser and platform, they replace the shared secret with public-key cryptography, and in doing so eliminate whole categories of attack rather than making them marginally harder. For a growth-stage SaaS company, moving to passwordless is both a real security upgrade and, increasingly, a competitive and enterprise-sales expectation.

How passkeys actually work

A passkey is a cryptographic key pair. When a user registers, their device generates a private key that never leaves the device (protected by the device's secure hardware) and hands your server the matching public key. To log in, your server sends a challenge; the device signs it with the private key, gated behind a local biometric or PIN, and your server verifies the signature with the public key it stored. The consequences fall out of the math. There is no shared secret to steal — your database holds only public keys, which are useless to an attacker. There is nothing for the user to type, so there is nothing to phish. And crucially, a passkey is cryptographically bound to your domain, so a user cannot be tricked into using it on a look-alike phishing site — the browser simply won't offer it. This is why passkeys are described as phishing-resistant, a property no password-plus-code scheme can claim.

What passwordless kills

• Phishing: the single biggest one. A domain-bound passkey can't be replayed on an attacker's site, which neuters the credential-harvesting playbook that drives most breaches.
• Credential stuffing and reuse: there's no reusable secret to spray from a breach dump, so the attacks that turn one company's leak into everyone's problem simply don't apply.
• Password database risk: you're no longer storing password hashes that become a liability the moment they leak. Public keys are safe to store in the clear.
• Password-reset overhead: no passwords means no 'forgot password' flow, which is both a support-cost sink and, via account-recovery, one of the most attacked paths in any app.
• MFA-fatigue and SMS interception: passkeys fold strong second-factor assurance into a single gesture, retiring the push-spam and SIM-swap weaknesses of SMS and push MFA.

Migrate gradually, not overnight

You do not flip a switch and delete passwords on Monday — a forced cutover locks out anyone whose device or habits aren't ready and generates a support fire. The proven path is incremental. First, add passkeys as an option alongside existing login, and let security-conscious and mobile users adopt them voluntarily. Then actively encourage enrollment — prompt users to add a passkey after a successful password login, framing it as faster and safer, which it genuinely is. Over time, make passwordless the default for new accounts, so the password path withers rather than being ripped out. Only once adoption is high do you consider retiring passwords for a given cohort. Throughout, meet users where their devices are: passkeys sync across a user's ecosystem (Apple, Google, Microsoft, and password managers all support this now), which resolved the old objection that losing a device meant losing access.

The parts teams underestimate

Two areas deserve more design attention than they usually get. The first is account recovery, which quietly becomes your new security frontier: once passkeys are strong, attackers pivot to the recovery flow, so a weak 'email me a reset link' backdoor undermines the whole scheme — recovery needs to be as thoughtfully secured as login itself, often with a second registered passkey or a hardware key as backup. The second is cross-device and enterprise reality: users have multiple devices, shared and managed devices exist, and enterprise buyers will expect passkeys to slot into their SSO and identity provider — so passwordless is not a bolt-on but a design consideration that touches your whole multi-tenant auth model. Getting these right is also what makes passwordless credible in a compliance context: phishing-resistant authentication is exactly the kind of control that strengthens a SOC 2 or HIPAA posture rather than just improving UX.

How Infiniti Tech Partners handles passwordless

We implement passkeys and WebAuthn as a phased migration, not a risky big-bang cutover: passkeys added alongside your existing login, enrollment prompts that drive real adoption, passwordless as the default for new accounts, and passwords retired only once a cohort is ready. We give the same care to the parts teams skip — hardened account recovery, cross-device sync, and clean integration with enterprise SSO and your multi-tenant model. The outcome is authentication that eliminates phishing and credential-stuffing instead of just slowing them down, with a login experience users actually prefer. If password resets and account-takeover risk have become a tax you're tired of paying, passwordless is how you stop paying it.