What encryption standard does AWS use on S3 buckets?

AWS uses the Advanced Encryption Standard (AES) with a 256-bit key size for encrypting objects in Amazon S3 buckets. AES is a symmetric encryption algorithm that provides a high level of security and is widely adopted for securing sensitive data. The choice of 256 bits as the key length is significant because it represents a balance between strong security and performance. AES-256 offers a higher level of security than AES-128, making it suitable for protecting critical and sensitive data stored in the cloud.

Additionally, AWS allows users to configure server-side encryption (SSE) for S3 buckets, enabling automatic encryption of data at rest using AES-256. This feature simplifies the management of encryption by eliminating the need for developers to handle encryption directly, thus reducing complexity and ensuring consistent security practices.

The other choices represent different encryption standards that are not used by AWS for S3 bucket encryption. RSA is an asymmetric encryption algorithm rather than symmetric, making it less suitable for encrypting large data objects in S3. AES-128, while a valid encryption method, does not provide the same level of security as AES-256. SHA-256 is a cryptographic hash function rather than an encryption standard, designed for integrity verification rather than encryption.