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Support for 3072-bit RSA keys in App Service managed certificate?

Edwin Otten 0 Reputation points
2025-11-19T10:55:43.2966667+00:00

My team uses the Managed certificate feature in Azure App Service and Azure Static Web App (which automatically renews certificates). Our organization policy is moving away from 2048-bit public keys and the Dutch National Cyber Security Centre recommends upgrading to 3072-bit:

The key length for RSA 2048-3071 has been downgraded to to be phased out. These guidelines pursue a cryptographic strength of 128 bits, following an RSA key length of 3,072 bits. Source: https://english.ncsc.nl/publications/publications/2025/06/26/security-guidelines-for-transport-layer-security-2025-05

 

When will the Managed certificate support 3072-bit RSA public keys? (either configurable or by default)

Azure App Service
Azure App Service

Azure App Service is a service used to create and deploy scalable, mission-critical web apps.

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  1. Anonymous
    2025-11-19T12:04:05.9466667+00:00

    Hi @Edwin Otten

    Azure App Service Managed Certificates, including those used by Azure Static Web Apps, currently support only RSA 2048-bit keys. Higher key sizes such as 3072-bit and 4096-bit are not supported in the managed certificate offering, and there has been no official announcement regarding future support for larger RSA key lengths.

    For environments that require RSA 3072-bit keys, such as those following the Dutch National Cyber Security Centre guidelines, a custom TLS certificate is required. Azure App Service fully supports uploading custom certificates with 3072-bit or 4096-bit RSA keys, and organizations can automate renewal through Azure Key Vault–based certificate rotation.

    Reference:

    If support for larger RSA key sizes in managed certificates is important for your scenario, you may consider submitting this request through the Azure Feedback platform so that the product team can review and prioritize it based on customer demand.

    Hope this helps!

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