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S3 bucket is created. Please refer the following page to create a S3 bucket. https://docs.aws.amazon.com/AmazonS3/latest/userguide/creating-bucket.html
KMS Key is created. Please refer the following page to create a KMS Key.https://docs.aws.amazon.com/kms/latest/developerguide/asymm-create-keykeys.html.
GuardDuty encrypts the findings data in your bucket by using an AWS KMS key. GuardDuty should have permission to access KMS key.
Please refer the following page to grant KMS key permission to GuardDuty: https://docs.aws.amazon.com/guardduty/latest/ug/guardduty_exportfindings.html
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