> For the complete documentation index, see [llms.txt](https://ysfang82.gitbook.io/development-notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ysfang82.gitbook.io/development-notes/aws-notes/service/kms.md).

# KMS

**Introduction**

* A regional service for at rest encryption
* Can be used with API call to encrypt / decrypt data

**Feature**

* Seamlessly integrated into:
  * EBS volumes
  * S3 objects
  * Redshift data
  * RDS data
  * SSM Parameter stores
  * Etc...
* Types:
  * Customer managed [CMK](< https://docs.aws.amazon.com/zh_tw/kms/latest/developerguide/concepts.html#master_keys>):
    * Managed by our own.
    * Possibility of rotation
    * Can add Key Policy
    * Can leverage for Envelop Encryption
  * AWS managed CMK:
    * Managed by AWS, we don't have access.
    * Used by AWS Service (S3, EBS, Redshift, etc.)
* Can only support encryption up to 4 KB of data per call. If data > 4 KB, use \
  Envelop Encryption.
* API calls are tracked in CloudTrail

**Usage**

* Dynamically and programmatically to [grant](https://docs.aws.amazon.com/kms/latest/developerguide/grants.html) the ability to use the key then revoking after the need is over. (more efficient than manipulating IAM)&#x20;
* To grant access to KMS to someone:
  * Make sure permission in Key Policy
  * Make sure permission in IAM Policy


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://ysfang82.gitbook.io/development-notes/aws-notes/service/kms.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.