Effective Cost Reduction Techniques for AWS KMS Keys

Answer: B.

Option A is incorrect because enabling key rotation would not help reduce the cost of accessing the keys.

Option B is CORRECT because data key caching stores data keys and related cryptographic material in a cache.

When you encrypt or decrypt data, the AWS Encryption SDK looks for a matching data key in the cache.

If it finds a match, it uses the cached data key rather than generates a new one.

Data key caching can improve performance, reduce cost, and help you stay within service limits as your application scales.

Option C is incorrect because creating aliases for the key would not impact how the key is used and not reduce the access request.

Option D is incorrect because providing a key policy would not impact how the key is used and not reduce the access request.

For more information on data key caching, please refer to the below URL:

https://docs.aws.amazon.com/encryption-sdk/latest/developer-guide/data-key-caching.html

The AWS Key Management Service (KMS) provides a secure and scalable way to generate, store, and manage cryptographic keys and use them to encrypt and decrypt data. However, using KMS can incur costs, especially when keys are accessed frequently. Therefore, to reduce the cost of accessing keys in AWS KMS, one can consider the following options:

A. Enable rotation of the keys: Key rotation is a security best practice that involves replacing old keys with new ones periodically. Enabling key rotation can help reduce the risk of key compromise and ensure that the keys remain fresh. In addition, AWS KMS provides automatic key rotation for certain types of keys, which can further reduce the cost of managing keys.

B. Use data key caching: Data key caching is a technique that involves caching the plaintext data keys used for encryption and decryption in memory or on disk. This can help reduce the number of calls made to KMS to generate new data keys, thereby reducing the cost of using KMS. However, data key caching can also introduce security risks, such as exposing plaintext data keys in memory or on disk, so it should be used with caution.

C. Create an alias of the key: AWS KMS allows you to create an alias for a key, which can make it easier to reference the key in your application. By using an alias, you can avoid hardcoding the key ID in your code and make it easier to switch to a different key if needed. However, creating an alias does not directly reduce the cost of accessing the key.

D. Use the right key policy: AWS KMS allows you to define fine-grained access controls for keys using key policies. By using the right key policy, you can limit access to the keys to only the users and roles that need them, which can help reduce the risk of unauthorized access and misuse of the keys. However, using the right key policy does not directly reduce the cost of accessing the key.

In conclusion, the most effective way to reduce the cost of accessing keys in AWS KMS depends on the specific use case and requirements. However, enabling key rotation and using data key caching are two commonly used techniques that can help reduce the cost of using KMS while maintaining security and compliance.