SSE-KMS and FIPS validation - is the default s3 key also FIPS validated? Or is a CMK the only FIPS validated option?

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I have only recently noticed that when you go into create an S3 bucket and select SSE-KMS it allows you to choose the default S3 KMS key or use your own KMS key. Unless I am mistaken, the default S3 key is the same key that SSE-S3 is using? Am I right about that? I am just concerned about ensuring my S3 buckets are configured with the FIPS validated encryption option. I know that SSE-S3 is not FIPS validated so my assumption was just that if the same key is being used then my only option for SSE-KMS would be to use my own KMS key.

2 Answers
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Accepted Answer

Sorry for the misunderstanding; I hope this can help.

SSE-S3 refers to the default encryption that Amazon S3 applies to all new object uploads using an automatically managed key. With SSE-S3, Amazon handles the encryption, key management, and key protection.

The AWS/s3 key refers to the default KMS key that is used for server-side encryption if a specific customer-managed key is not specified. Like SSE-S3, it uses a key managed by AWS KMS but gives you more control over access since it is associated with your AWS account.

Two "key" differences are:

  • SSE-S3 is fully managed by Amazon S3 while aws/s3 gives you control by associating the encryption with your AWS account.

  • Objects encrypted with the aws/s3 key can be accessed based on the IAM policies associated with your AWS account.

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Julian
answered 3 months ago
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EXPERT
reviewed 3 months ago
  • Hmm, that makes sense to me but it does sound like the bottom line would be that as far as FIPS validation is concerned SSE-S3 and SSE-KMS using that aws/s3 key SHOULD run into the same issue since it is using that same key. But if you use SSE-KMS with a CMK then you would be able to comply with FIPS 140-2 validation for compliance purposes.

  • If FIPS compliance and being in control of your encryption key is important to you, then you should use SSE-KMS and CMK.

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Hello,

The default S3 Key will be an encryption key managed by AWS. You do not see this type of key or even manage it in the console.

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Julian
answered 3 months ago
  • What I mean is if you select SSE-KMS you will see both the AWS managed key (aws/s3) and your customer-managed keys appear in that list when you are selecting a key.

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