Amazon Web Services Updated DVA-C02 Exam Questions and Answers by ishaaq

The key security requirement is to limit both scope and duration of credentials used by an external application (running outside AWS). The most secure AWS-native way to do this is to use temporary security credentials issued by AWS Security Token Service (STS), rather than long-term IAM user access keys. Temporary credentials have a short, configurable lifetime and are tied to permissions defined by an IAM role and (optionally) session policies, which enforces least privilege.

With STS AssumeRole , the application requests temporary credentials for a specific IAM role . The role’s permission policy strictly defines what AWS actions and resources the session can access. The resulting credentials automatically expire, reducing the blast radius if the credentials are exposed. This approach also supports best practices such as rotating session credentials frequently and using external IDs and condition keys (where applicable) to reduce confused-deputy risks.

Options A and B rely on long-term IAM user credentials . Even if stored in environment variables or AWS Secrets Manager, these are still persistent credentials that do not inherently meet the “limit duration” requirement and are higher risk if leaked. Secrets Manager improves storage and rotation workflows, but it does not change the fact that IAM user access keys are long-lived by default.

Option C (GetFederationToken) is not the best fit here. Federation tokens are typically used to obtain temporary credentials for a federated user session and are commonly associated with IAM users (or scenarios like providing temporary access to third parties) rather than the standard, role-based pattern for an application assuming permissions. The most direct and widely recommended method for applications needing scoped, time-bound AWS access is AssumeRole .

Therefore, D is the most secure solution: create an IAM role with least-privilege permissions and have the application call STS AssumeRole to obtain short-lived credentials for AWS API calls.

Step-by-Step Breakdown:

Requirement Summary:

In-transit encryption (when data is moving between client and S3)

Encryption at rest using AWS KMS keys (which are rotatable on-demand)

Option A: Write an S3 bucket policy to allow only encrypted connections over HTTPS by using permissions boundary

Incorrect: Permissions boundaries are for IAM policy control, not S3 bucket policies.

Also, encryption enforcement in-transit is not achieved through permissions boundaries.

Option B: Configure an S3 bucket policy to enable client-side encryption

Incorrect: AWS does not enforce client-side encryption via S3 bucket policies.

Client-side encryption must be handled entirely by the application.

Also, KMS is for server-side encryption, not client-side.

Option C: Configure the application to encrypt the objects by using an AWS KMS customer managed key before uploading the objects

Correct: This fulfills the requirement of encrypting objects at rest using a KMS CMK, which can be rotated.

You can specify the KMS key using the SSE-KMS option when putting an object.

Option D: Write an S3 bucket policy to allow only encrypted connections over HTTPS by using the aws:SecureTransport condition

Correct: This enforces in-transit encryption, which ensures that only HTTPS connections are allowed.

This is the AWS-recommended way to enforce encryption in transit via bucket policy.

Option E: Configure S3 Block Public Access settings for the S3 bucket to allow only encrypted connections over HTTPS

Incorrect: Block Public Access is used to prevent public exposure of the bucket.

It has nothing to do with encryption enforcement, whether in transit or at rest.

Using SSE-KMS: https://docs.aws.amazon.com/AmazonS3/latest/userguide/UsingKMSEncryption.html

aws:SecureTransport condition in bucket policies: https://docs.aws.amazon.com/AmazonS3/latest/userguide/amazon-s3-policy-keys.html

Server-side encryption with AWS KMS: https://docs.aws.amazon.com/AmazonS3/latest/userguide/serv-side-encryption.html