What is S3 server-side encryption?

Key takeaways:
Server-side encryption is crucial for securing S3 buckets.
There are three main types of server-side encryption: SSE-S3, SSE-KMS, and SSE-C.
Key management is essential for SSE-KMS and SSE-C to ensure data security.

Amazon S3 buckets often store sensitive or confidential data, as well as data that should remain unaltered by unauthorized users. To safeguard such data, you can fortify your S3 buckets by employing server-side encryption. By implementing these encryption methods, you not only enhance data security but also fulfill the necessary regulatory obligations, reducing the risk of fines and legal consequences associated with non-compliance.

Types of S3 encryptions

The following are the types of S3 encryption:

Client-side encryption: This is useful for encryption in transit and at rest. In this type of encryption, we encrypt the data on our end before sending it to be stored in the S3 bucket.
Server-side encryption: This is useful for encryption at rest. In this type of encryption, plain data is sent for storage, and S3 takes care of the encryption using the specified encryption keys.

Server-side encryption

Server-side encryption provides encryption for data stored in an S3 bucket. When a user uploads data, it is encrypted before being stored. When the user retrieves the data, it is decrypted and then presented to them. This means that while the user interacts with unencrypted data, the data remains secure throughout its storage and retrieval process, adding an extra layer of security.

Types of server-side encryption

Here are the types of server-side encryption:

Encryption using Amazon S3-managed keys (SSE-S3)

The keys used for encryption are managed by S3. This is the default encryption type for S3. This encryption is free of cost. When an object is uploaded to the bucket, S3 encrypts the data using the default encryption keys and then stores it in the bucket. Upon retrieval, this data is decrypted and then provided to the user. The encryption/decryption process takes place behind the scenes, so the user sees simple data writing and reading when making requests to S3.

Encryption using AWS Key Management Service-managed keys (SSE-KMS)

The keys used for encryption are managed by AWS. These keys first need to be created and then can be used to encrypt S3 buckets. This type of encryption provides us with more control over the encryption keys.

When a KMS key is specified as the encryption key for an S3 bucket, a data key is generated using that KMS key. This encrypted version of this data key is stored as the metadata of the S3 bucket.

When an object is uploaded to the bucket:

S3 requests the KMS to decrypt the encrypted data key.
KMS decrypts that key and sends the plaintext key to S3.
S3 uses an encryption algorithm to encrypt the input object and stores the encrypted object in the bucket.
S3 deletes the plaintext key, so in case of unauthorized access, this key is not compromised, and the unauthorized user cannot decrypt the data.
Similarly, when we try to read the object, S3 again obtains the decrypted version of the data key and then uses that key to decrypt the data, which is then returned to the requesting entity.

This encryption is further divided into two types:

Simple encryption: In this type, S3 uses the specified KMS key to encrypt the data before storing it on the bucket.
Dual-layer encryption: In this type, S3 uses the specified KMS key to encrypt the data twice using different encryption algorithms. The encrypted data is then stored in the bucket.

Encryption using Customer-Provided keys (SSE-C)

The keys used for encryption are provided and managed by the customer. This type of encryption provides us with complete control over the encryption keys.

In summary, server-side encryption in Amazon S3 is an essential component of a robust data security strategy. Encrypting Amazon S3 buckets serves as a crucial security measure for protecting sensitive or confidential data, ensuring data integrity, and complying with regulatory requirements. Server-side encryption, one of the methods available for securing data at rest, automatically encrypts data upon upload to an S3 bucket and decrypts it when retrieved, maintaining data security throughout its life cycle.