The default encryption for data at rest in Amazon S3 is indeed AES-256 encryption. This encryption standard is widely recognized for its high level of security and efficiency.
Amazon S3 provides the option for server-side encryption, specifically Amazon S3 Server-Side Encryption (SSE), which automatically encrypts data when it is uploaded to S3 and decrypts it when accessed. AES-256 is the encryption algorithm used in this default configuration, ensuring that your data is protected while stored in S3 buckets.
This choice is particularly important because, without encryption, data at rest can be vulnerable to unauthorized access. By using AES-256, AWS adheres to industry standards for encryption, providing users with strong security guarantees.
The other choices represent either different types of encryption or hashing functions. RSA is an asymmetric encryption algorithm often used for secure data transmission rather than for data at rest. AES-128 is a variant of AES but does not provide the same level of security as AES-256. SHA-256 is a hashing algorithm designed for data integrity verification, not for encryption. Thus, AES-256 stands out as the correct choice for securing data at rest in S3.