Johannes

The SDK returns [this object](https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/clients/client-kms/interfaces/getpublickeycommandoutput.html). Of particular interest is PublicKey, which is a Uint8Array (i.e. it's not a base64-encoded string).

Edit: This comment is in response to a now-deleted comment pointing out [this line](https://github.com/aws/aws-cdk/blob/17b09554392cf0e8ff18be3d0cc73273d76635ed/packages/%40aws-cdk/custom-resources/lib/aws-custom-resource/runtime/index.ts#L30) as a potential cause for the error: ```ts const childKey = Buffer.isBuffer(child[key]) ? child[key].toString('utf8') : child[key];...