# [DL.CS.2] Sign code artifacts after each build
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 **Category:** RECOMMENDED 

 Code signing is the process of attaching a digital signature to build artifacts like binaries, containers, and other forms of packaged code to enable verifying its integrity and authenticity. Signing code artifacts minimizes risk of using or distributing tampered or counterfeit software. 

 Cryptographically sign code artifacts during the build process. Ideally this occurs after testing and before publishing to production. Follow [best practices for timestamping](https://www.digicert.com/blog/best-practices-timestamping) while signing. Timestamping provides a verified date and time of the signing, serving as evidence that the code artifact existed and met the signature criteria while the certificate was still valid. To safeguard operations, ensure that the validity of the signed code artifact is recognized even after the signing certificate itself has expired. 

 Store signatures in a location accessible to users and systems that need to verify signed code artifacts. When using [Open Containers Initiative (OCI)](https://opencontainers.org/) compliant artifact registries, it is encouraged to store digital signatures alongside the build artifacts being signed. This enables a consolidated retrieval process and allows verification systems to easily locate and validate signatures. Just as with artifacts, signatures can accumulate over time. Implement a lifecycle policy that archives or deletes older signatures that are no longer needed to help manage storage costs. 

 After a signature has been stored, it should be immutable so that the signature cannot be tampered with or replaced. Use fine-grained access controls to ensure that only authorized entities can push or modify artifacts and their corresponding signatures. Regularly back up your digital signatures. Having a backup ensures you can still verify the integrity and authenticity of your artifacts in the event of storage failures. All access and operations on stored signatures should be logged to support forensic analysis and to adhere to compliance requirements. 

 Implement cryptographic signing of artifacts during the build process. Ideally this occurs after testing and before publishing to production. This helps ensure the integrity of the artifacts and confirms their authenticity. We recommend using a managed service like [AWS Signer](https://docs.aws.amazon.com/signer/latest/developerguide/Welcome.html) to reduce the complexity that comes with managing public key infrastructure. Refer to [AWS Signer workflows](https://docs.aws.amazon.com/signer/latest/developerguide/workflows.html) for guidance that fits your use case. 

 For more control over the signing process or for complex use cases, you can create and manage your own code signing platform using Public Key Infrastructure (PKI). While this approach offers precise control, it requires consistent upkeep and adherence to best practices. [AWS Private Certificate Authority](https://aws.amazon.com/private-ca/) is a managed private CA service that helps you manage the lifecycle of your private certificates easily, without the investment and ongoing maintenance costs of operating your own private CA. 

**Related information:**
+  [AWS Well-Architected Sustainability Pillar: SUS05-BP03 Use managed services](https://docs.aws.amazon.com/wellarchitected/latest/sustainability-pillar/sus_sus_hardware_a4.html) 
+  [Using AWS Signer workflows](https://docs.aws.amazon.com/signer/latest/developerguide/workflows.html) 
+  [Configuring code signing for AWS SAM applications - AWS Serverless Application Model](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/authoring-codesigning.html) 
+  [Security Considerations for Code Signing](https://nvlpubs.nist.gov/nistpubs/CSWP/NIST.CSWP.01262018.pdf) 
+  [Code signing using AWS Certificate Manager Private CA and AWS Key Management Service asymmetric keys](https://aws.amazon.com/blogs/security/code-signing-aws-certificate-manager-private-ca-aws-key-management-service-asymmetric-keys/)