Tutorial / Cram Notes
AWS offers several services that allow users to manage encryption keys, including AWS Key Management Service (KMS) and AWS CloudHSM. These services help in maintaining control over encryption keys and, by extension, over the data.
AWS Key Management Service (KMS)
AWS KMS is a managed service that makes it easy for you to create and control encryption keys used to encrypt your data. One of the features of AWS KMS is the ability to import your own key material. To do this, you must follow several steps:
Create a Customer Master Key (CMK) without key material:
AWS KMS allows you to create a CMK with no key material; this is specifically designed for subsequent key material import.
Download the public key and import token:
AWS KMS provides a public key and an import token that are used to encrypt the key material on the client’s side before uploading it to AWS.
Encrypt your key material:
Use the public key provided by AWS KMS to encrypt your key material locally.
Import key material:
Once encrypted, the key material can be imported into the CMK using the import token.
Use the CMK in AWS services:
Once the key material is imported, the CMK can be used within services that integrate with AWS KMS, such as Amazon S3, for encrypting data.
To remove the key material from AWS KMS, simply use the AWS Management Console, AWS CLI, or SDKs to delete the key material, after which, the CMK becomes unusable until new key material is reimported.
AWS CloudHSM
AWS CloudHSM provides hardware security modules in the AWS Cloud, allowing you to generate and use your own encryption keys. When using AWS CloudHSM, you have the option to import your own key material as well:
Initialize the HSM:
Create and initialize an HSM cluster and make sure you have an HSM client.
Generate an HSM key:
Use the HSM client to generate a key directly on the CloudHSM cluster.
Wrap the key for export:
If you want to bring your key into CloudHSM from another source, you will need to wrap it using a key wrapping key (KWK) that only CloudHSM knows internally.
Import the key into CloudHSM:
After wrapping the key material, it can be imported directly into CloudHSM and managed thereafter.
To remove key material from AWS CloudHSM, you can use the HSM client to delete the keys. Note that once deleted, the keys cannot be recovered.
Comparison
Here is a comparison of KMS and CloudHSM in terms of key material import and deletion:
| Feature | AWS KMS | AWS CloudHSM |
|---|---|---|
| Key Generation | Server-side; by AWS and customers | Customer-side; within HSM |
| Key Storage | Keys stored and managed by AWS KMS | Keys stored and managed within customer’s HSM |
| Key Import | Encrypted by customer-specified key before import | Wrapped by a KWK before import |
| Key Deletion | Key material can be deleted from console/CLI/SDK | Keys can be deleted using the HSM client |
| Management | Fully managed by AWS | Customer manages the HSM but AWS manages the infrastructure |
| Integration with AWS Services | Broad integration with AWS services | Can be used by services that support CloudHSM keys |
| Compliance Certifications | FIPS 140-2 | FIPS 140-2 Level 3 |
| Use Case | Suitable for users who require integration with AWS services and managed service | Suitable for users who require direct control over their HSM and additional compliance certifications |
Example
Here is an example using the AWS CLI to import key material into a CMK in AWS KMS:
<!– language: shell –>
# Create a CMK without material
aws kms create-key –origin EXTERNAL –description “CMK with imported key material”
# Download the public key and import token
aws kms get-parameters-for-import –key-id <key-id> –wrapping-algorithm RSAES_OAEP_SHA_256 –wrapping-key-spec RSA_2048
# Encrypt the key material using the provided public key (usually this is done outside the CLI with a separate tool)
# Import the key material (key material file should be encrypted)
aws kms import-key-material –key-id <key-id> –import-token <token> –encrypted-key-material fileb://<encrypted-key-material-file>
For each service, AWS provides detailed step-by-step instructions and the necessary commands to import and manage key material securely. It’s important to follow these instructions carefully to ensure the security and integrity of your encryption keys.
Practice Test with Explanation
True or False: AWS Key Management Service (KMS) allows you to import your own key material for use with AWS services.
- A) True
- B) False
Correct Answer: A) True
Explanation: AWS KMS does allow customers to import their own cryptographic key material to be used with the KMS service.
What does AWS provide to encrypt the key material before importing it into KMS?
- A) S3 server-side encryption
- B) AWS Import/Export Snowball
- C) A wrapping key
- D) Amazon Macie
Correct Answer: C) A wrapping key
Explanation: AWS provides a wrapping key along with an import token, which is used to securely import customer key material into AWS KMS.
What command is used to import key material into the AWS Key Management Service (KMS) using the AWS CLI?
- A) aws kms import-key-material
- B) aws kms create-key
- C) aws kms enable-key
- D) aws s3 cp
Correct Answer: A) aws kms import-key-material
Explanation: The ‘aws kms import-key-material’ command is specifically used to import key material into KMS for use with customer master keys (CMKs).
True or False: Customer-provided key material in AWS KMS can be set to automatically expire.
- A) True
- B) False
Correct Answer: A) True
Explanation: You can specify an expiration date for the imported key material, after which AWS KMS deletes the key material and you can no longer use the CMK for cryptographic operations.
When the imported key material expires or is deleted, what happens to the AWS resources that were encrypted with that key material?
- A) They are automatically decrypted
- B) They remain encrypted but become inaccessible
- C) They are automatically re-encrypted with a new key
- D) They are deleted alongside the key material
Correct Answer: B) They remain encrypted but become inaccessible
Explanation: Once the key material expires or is deleted, the AWS resources remain encrypted with the key material, but they can no longer be decrypted, hence becoming inaccessible until new key material is imported or the key is enabled again.
In which of the following AWS services can you import your own key material for encryption?
- A) AWS KMS
- B) AWS CloudHSM
- C) Both A and B
- D) Neither A nor B
Correct Answer: C) Both A and B
Explanation: AWS allows customers to import their own key material for encryption in both AWS Key Management Service (KMS) and AWS CloudHSM.
True or False: Once imported, the key material cannot be removed from the AWS Key Management Service (KMS).
- A) True
- B) False
Correct Answer: B) False
Explanation: AWS KMS allows customers to delete the imported key material from the service, which makes the corresponding customer master key unusable for cryptographic operations.
What is the process of managing your own cryptographic keys outside of AWS and then importing them when needed called?
- A) Bring Your Own Key (BYOK)
- B) Custom Key Store
- C) Server-Side Encryption
- D) Client-Side Key Generation
Correct Answer: A) Bring Your Own Key (BYOK)
Explanation: BYOK refers to the process where customers generate and manage their cryptographic keys in their own on-premises environments or in another secure environment, and then import them into AWS for use in the cloud.
What should you do to continue using a customer master key (CMK) in AWS KMS when the key material has expired?
- A) Create a new CMK
- B) Re-import the key material
- C) Enable automatic key rotation
- D) Contact AWS Support
Correct Answer: B) Re-import the key material
Explanation: When the key material for a CMK expires, you can re-import the same or new key material to continue using that CMK.
True or False: Customer-provided key material in AWS can be imported only through the AWS Management Console.
- A) True
- B) False
Correct Answer: B) False
Explanation: Customer-provided key material can be imported into AWS KMS using the AWS Management Console, AWS CLI, or AWS SDKs.
Interview Questions
Can you explain the process to import customer-provided key material into AWS Key Management Service (KMS)?
To import customer-provided key material into AWS KMS, you must first create a symmetric customer master key (CMK) without material, download the public key and import token, encrypt the key material using the public key, and then upload the encrypted key material along with the import token. AWS uses the import token to associate the key material with the correct CMK.
How long are the import tokens and public keys, provided by AWS KMS for key material import, valid?
The import tokens and public keys provided by AWS KMS for key material import are valid for 24 hours from the time they are downloaded. Beyond this time frame, you would need to download a new public key and import token to proceed with the import process.
What is the importance of having a key material expiration date when importing your key into AWS KMS?
Setting a key material expiration date is critical for ensuring that your key material does not remain on AWS indefinitely. It allows you to enforce key rotation policies and adhere to compliance requirements by automatically expiring the key material after a certain period, which in turn, necessitates re-import or deletion of key material.
What happens when the customer-provided key material in AWS KMS expires or is deleted?
When customer-provided key material expires or is deleted in AWS KMS, the associated CMK becomes unusable for cryptographic operations. However, you retain access to the CMK and can re-import new key material or delete the CMK as necessary. Even after deletion, you have a grace period during which you can still decrypt any previously encrypted data.
Can you delete customer-provided key material from AWS KMS? If so, how?
Yes, you can delete customer-provided key material from AWS KMS. To do this, you use the ‘DeleteImportedKeyMaterial’ API operation. Once deleted, the CMK remains in AWS without key material and can no longer be used to encrypt or decrypt data until new material is imported.
How does AWS ensure the security of imported key material when using AWS KMS?
AWS secures imported key material using hardware security modules (HSMs) that are designed to meet various compliance standards. Additionally, the service uses strong encryption and secure access controls to prevent unauthorized access to the key material.
What are the limitations when importing key material into AWS KMS?
When importing key material into AWS KMS, there are several limitations to consider:
– Only symmetric CMKs can have imported key material.
– The key material must be a 256-bit symmetric key.
– You cannot import key material into an existing AWS-managed CMK.
– AWS doesn’t allow direct access to the key material nor can you extract it later.
Is it possible to enable automatic rotation for CMKs with imported key material in AWS KMS?
No, AWS KMS does not support automatic rotation for CMKs with imported key material. If you wish to rotate these keys, you must manually import new key material to the CMK when appropriate.
How can you ensure that key material is never permanently stored in AWS KMS by setting up an automatic deletion policy?
To ensure key material is not permanently stored, you can set an expiration date for the key material at the time of import. Once this date is reached, the key material is automatically deleted. Additionally, you can also use AWS CloudWatch Events to trigger a Lambda function to delete key material after a certain period.
How do you monitor the use of customer-provided key material in AWS KMS?
You can monitor the use of customer-provided key material in AWS KMS using AWS CloudTrail, which records all API calls to AWS KMS, including those related to imported key material. This allows you to audit key usage, identify unusual patterns, and ensure compliance with your security policies.
What steps should you take if you suspect that the customer-provided key material is compromised?
If you suspect that key material is compromised, you should immediately delete the imported key material from AWS KMS to prevent its use, rotate the key material by generating and importing new material, and then re-encrypt your data using the new key. It’s also essential to investigate the cause of the compromise and take steps to prevent future occurrences.
Is there a difference between disabling a CMK and deleting imported key material in AWS KMS, and if so, what is it?
Yes, there is a difference between disabling a CMK and deleting the imported key material. Disabling a CMK makes it inactive and unusable for any cryptographic operations but retains the key material and its metadata. Deleting imported key material removes the key material from the CMK, rendering it unusable, but the CMK itself remains, along with its metadata. The latter requires you to re-import key material to re-enable the CMK.
This blog post is incredibly helpful! I’ve been trying to understand how to securely import and remove customer-provided key material, and this really breaks it down.
Can someone explain the difference between importing keys manually and using AWS KMS?
The step-by-step guide for key import is very well-written. Can anyone share their experience with real-world applications?
Thanks a lot for this guide!
What happens if the imported key material is compromised? How can we ensure it’s securely removed?
Great post!
How effective is AWS KMS for key management in a multi-region deployment?
I appreciate the detailed explanation provided here.