"All data stored in Google Cloud is encrypted at the storage level using AES256..." (Google)
"Amazon S3 server-side encryption uses one of the strongest block ciphers available to encrypt your data, 256-bit Advanced Encryption Standard (AES-256)." (Amazon)
"With Office 365, your data is encrypted at rest and in transit, using several strong encryption protocols, and technologies that include ... Advanced Encryption Standard (AES)." (Microsoft)