🔐 Retro-Fitting SSO: Where the Real ROI Lives
Most discussions about SSO focus on new applications. But after 20+ years in .NET, I’ve found the biggest wins come from modernizing the legacy web apps that are already running the business day-to-day.
The tension is real: users are productive with their current login. They don’t want surprise changes.
But SSO brings genuine benefits - reduced password fatigue, faster onboarding, better security controls.
The solution I implemented was a hybrid authentication approach: ✅ Both the old username and password login and SSO methods coexisting in the same application. ✅ Zero disruption. ✅ Users choose when to switch.
How this worked in practice:
- User data preparation: unconventional user names need updated or account linked to user’s Microsoft login.
- Dark Launch: initially hidden from normal view, to allow thorough live testing
- Parallel migration: Users have option to sign in either way, adopting SSO at their own pace
- Easy rollback: One configuration change returns to legacy auth if needed
- Minimal database changes: Supporting passwordless accounts required surprisingly few schema changes
- Enterprise-ready: Full Microsoft Entra ID integration with comprehensive audit logging
For details on the hybrid approach taken, and the main gotchas along the way, please see my article https://www.linkedin.com/pulse/retrofitting-legacy-net-application-single-sign-paul-logan-fxcme.
The patterns used here translate well to other legacy application migrations - whether you’re moving from Forms Authentication to claims-based identity, or modernizing desktop applications.
#EnterpriseApplications #SSO #LegacyModernization