Encryption technique selection (for example, client-side, server-side, symmetric, asymmetric)

Can you explain the difference between symmetric and asymmetric encryption and when you would use each one in AWS?

Symmetric encryption uses the same key for both encryption and decryption of data, making it faster but less secure for sharing across the internet. Asymmetric encryption uses a pair of keys, a public key for encryption, and a private key for decryption, making it more secure for data transmission. In AWS, symmetric encryption is often used for Amazon S3 object encryption with AWS-managed keys (SSE-S3), while asymmetric encryption is suited for securing data transmission and sharing encrypted data between different parties, such as using AWS Key Management Service (KMS) with customer-managed keys for creating and managing cryptographic keys and their use across AWS services.

What are some considerations when choosing between client-side and server-side encryption in AWS?

When choosing client-side encryption, you retain control of the encryption process and keys. This method is preferable when data confidentiality is paramount, as it ensures data is encrypted before it leaves the client environment. However, it introduces complexity and requires key management. Server-side encryption is managed by AWS, simplifying the process as AWS handles the encryption/decryption and key management, often desired for ease of use and integration with AWS services. Consider your regulatory requirements, the sensitivity of data, performance impacts, and operational overhead when choosing.

When would you use AWS KMS for encryption, and how does it enhance security?

AWS KMS is used for creating and managing cryptographic keys and their use across AWS services. When you need to secure sensitive data, ensure compliance with standards, and maintain control over the keys used for encryption and decryption, AWS KMS is a suitable choice. It enhances security through central key management, encryption across services without managing custom encryption code, built-in auditing capabilities with AWS CloudTrail, and it supports both symmetric and asymmetric keys to fit various use cases.

How does AWS Certificate Manager (ACM) work with encryption, and what type of encryption does it support?

AWS Certificate Manager (ACM) is used to provision, manage, and deploy public and private SSL/TLS certificates used for securing network communications and establishing the identity of websites over the internet. ACM provides automatic certificate renewal and deployment, simplifying the certificate management lifecycle. It supports asymmetric encryption using public and private SSL/TLS certificates, enhancing the security of data in transit.

Can you describe envelope encryption and how AWS implements this technique?

Envelope encryption is a practice where you encrypt the plaintext data with a data encryption key (DEK), and then encrypt the DEK with a root key or master key, typically a key encryption key (KEK). AWS implements envelope encryption using AWS KMS. For instance, in Amazon S3 when using server-side encryption with AWS KMS, the object is encrypted with a unique DEK, and the DEK is then encrypted with a customer master key (CMK). This approach ensures the security of the encrypted data while allowing efficient management and protection of the key used to encrypt the DEK.

When should you use AWS managed keys versus customer managed keys?

AWS managed keys (SSE-S3) are suitable for use cases where you need server-side encryption and are comfortable with AWS managing the keys’ lifecycle and security. These are good for general use cases that do not require specific fine-grained key policies or audit trails. Customer managed keys, on the other hand, provide greater control and should be used when you need to set specific permissions on keys, audit their use, or implement compliance controls. They allow detailed key policies, key rotation controls, and the ability to use the keys outside of AWS (if required).

What security benefits does the AWS CloudHSM service provide for encryption key management?

AWS CloudHSM provides a hardware security module (HSM) in the AWS Cloud that enables you to generate and use your own encryption keys within the HSM’s tamper-resistant hardware. CloudHSM helps you meet compliance requirements for sensitive data protection by offering a dedicated hardware appliance for key management, thus ensuring that keys are managed within a secure, single-tenant HSM. It also helps maintain a strong separation of duties by giving you control over key access and operations.

How does Amazon S3 Object Encryption provide security for data at rest, and what are the encryption options available?

Amazon S3 Object Encryption provides security for data at rest by encrypting objects before saving them onto the S3 storage and decrypting them upon retrieval. The encryption options available are:

• Server-Side Encryption with Amazon S3-Managed Keys (SSE-S3): Each object is encrypted with a unique key and provides a strong level of security with minimal operational burden.
• Server-Side Encryption with AWS KMS-Managed Keys (SSE-KMS): Offers additional security controls, such as key management and auditing.
• Server-Side Encryption with Customer-Provided Keys (SSE-C): Customers manage their own encryption keys.
• Client-Side Encryption: The data is encrypted on the client’s side before uploading to Amazon S3; the client is responsible for key management.

Describe a scenario where you would implement AWS KMS multi-region keys and the advantages they provide.

AWS KMS multi-region keys are beneficial when you have applications that are geographically distributed across multiple AWS regions and require consistent and redundant key usage for encryption across these regions. For instance, if you have data replicated in two different AWS regions for disaster recovery purposes, using multi-region keys ensures you can encrypt and decrypt the replicated data in both regions independently while managing the keys centrally. Advantages include ensuring business continuity, simplified management of keys across regions, and potentially reducing latency in key access.

In what situations would it be more appropriate to use a custom key store instead of the default AWS KMS key store, and how does AWS CloudHSM support this?

A custom key store may be more appropriate when your organization is obligated by compliance or policy reasons to manage the key material in dedicated, single-tenant hardware, fully under your control. AWS CloudHSM supports the creation of a custom key store in KMS by providing the HSMs where you have total control over your keys. By using a custom AWS KMS key store backed by your own CloudHSM cluster, you meet the requirements for hardware-based key management while also benefiting from AWS KMS’s integration with AWS services for encrypting data.