This checkbox is especially useful when you need to perform some forensic investigation into a security threat as it ensures that your log files have not been tampered with or modified at all from when they were written to your bucket in Amazon S3. To enforce this validation, CloudTrail uses algorithms such as SHA-256 for hashing and SHA-256 with RSA for digital signing:
Every time a new log file is delivered to S3 with validation enabled, CloudTrail will create a hash for it. In addition to this, and once an hour, CloudTrail will also create another file called a digest file that references each and every log file that was delivered within that hour, along with the associated hash. These digest files are signed using a private key of a public/private key pair used by CloudTrail for that region. Using the associated public key, you can then validate the digest files, which are stored in the same S3 bucket as your logs but in a different folder.
If you have...