Amazon Bedrock AgentCore Identity now supports Private Key JWT auth for agents

Amazon Bedrock AgentCore Identity has introduced support for Private Key JWT client authentication, allowing agents to authenticate to downstream identity provider token endpoints using a signed JSON Web Token (JWT) instead of a shared OAuth 2.0 client secret. The private key is stored securely in AWS Key Management Service (AWS KMS), and the corresponding public key is registered with the identity provider. When an agent requests a token, AgentCore Identity builds a short-lived JWT assertion, signs it using the KMS asymmetric key via the kms:Sign operation, and sends the signed assertion to the identity provider's token endpoint. The provider verifies the signature against the registered public key and returns an access token. The private key never leaves KMS, significantly reducing the risk of credential exposure.

This feature supports three OAuth 2.0 grant flows: machine-to-machine (M2M) where the agent acts as itself using client_credentials grant; on-behalf-of (OBO) where the agent exchanges an inbound user token for a downstream token representing that user; and user-delegated access where the user authorizes the agent interactively via authorization code grant. The process requires configuring a credential provider on the AWS Management Console with the client ID, KMS key ARN, and signing algorithm (RS256, PS256, or ES256). AWS CloudTrail records all authentication events for auditing. This approach strengthens security for AI agents that need to access protected APIs, especially in enterprise environments where zero-trust and least-privilege principles are critical.